Double-sided solar cell and preparation method therefor

Abstract

Disclosed are a double-sided solar cell and a preparation method therefor. The double-sided solar cell comprises: a silicon wafer having a PN junction, and a front first silicon oxide layer, a front second silicon oxide layer, a front first nitrogen-containing silicon compound layer, a front second nitrogen-containing silicon compound layer, and a front third silicon oxide layer that are located on one side of an N-type layer of the silicon wafer and are sequentially stacked along a direction away from the silicon wafer; and a passivation layer, a back silicon oxide layer, a back first nitrogen-containing silicon compound layer, and a back second nitrogen-containing silicon compound layer that are located on one side of a P-type layer of the silicon wafer and are sequentially stacked along the direction away from the silicon wafer.

Claims

1. A bifacial solar cell, comprising a silicon wafer having a PN junction, and a front-side first silicon oxide layer, a front-side second silicon oxide layer, a front-side first nitrogen-containing silicon compound layer, a front-side second nitrogen-containing silicon compound layer and a front-side third silicon oxide layer that are located on the N-type side of the silicon wafer and stacked in sequence in a direction away from the silicon wafer; a passivation layer, a back-side silicon oxide layer, a back-side first nitrogen-containing silicon compound layer and a back-side second nitrogen-containing silicon compound layer that are located on the P-type side of the silicon wafer and stacked in sequence in the direction away from the silicon wafer, wherein each of the front-side first nitrogen-containing silicon compound layer and the back-side first nitrogen-containing silicon compound layer is a SiN.sub.x1 layer, wherein x1 is independently 0.75 to 1.34, and wherein the front-side second nitrogen containing silicon compound layer is a SiN.sub.x2/SiN.sub.x3/SiO.sub.xN.sub.y stacked structure stacked in sequence in the direction away from the silicon wafer, and the back-side second nitrogen-containing silicon compound layer is a SiN.sub.x2/SiN.sub.x3 stacked structure stacked in sequence in the direction away from the silicon wafer, wherein x2 is 0.75 to 1.34, x3 is 0.75 to 1.34, x is 1 to 2, y is 1 to 2, and x1>x2>x3.

2. The bifacial solar cell according to claim 1, wherein each of the front-side first silicon oxide layer, the front-side second silicon oxide layer, the front-side third silicon oxide layer and the back-side silicon oxide layer is a SiO.sub.2 layer.

3. The bifacial solar cell according to claim 1, wherein the front-side second silicon oxide layer, the front-side third silicon oxide layer and the back-side silicon oxide layer are electrodeposited silicon oxide layers.

4. The bifacial solar cell according to claim 1, wherein the front-side first silicon oxide layer is a thermal silicon oxide layer.

5. The bifacial solar cell according to claim 1, wherein the front-side second silicon oxide layer has a refractive index of 1.4 or more.

6. The bifacial solar cell according to claim 1, wherein the passivation layer has a thickness of 10 nm or more.

7. The bifacial solar cell according to claim 1, wherein the passivation layer is an aluminum oxide layer.

8. The bifacial solar cell according to claim 1, wherein the bifacial solar cell further comprises a silver electrode.

9. The bifacial solar cell according to claim 1, wherein a silver electrode on the N-type side of the silicon wafer passes through the front-side first silicon oxide layer, the front-side second silicon oxide layer, the front-side first nitrogen-containing silicon compound layer, the front-side second nitrogen-containing silicon compound layer and the front-side third silicon oxide layer.

10. The bifacial solar cell according to claim 1, wherein a silver electrode on the P-type side of the silicon wafer passes through the back-side silicon oxide layer, the back-side first nitrogen-containing silicon compound layer and the back-side second nitrogen-containing silicon compound layer.

11. The bifacial solar cell according to claim 1, wherein the front-side second silicon oxide layer has a thickness of 5 nm or more.

12. The bifacial solar cell according to claim 1, wherein the front-side first nitrogen-containing silicon compound layer has a refractive index of 2.0 or more.

13. The bifacial solar cell according to claim 1, wherein the front-side first nitrogen-containing silicon compound layer has a thickness of 15 nm or more.

14. The bifacial solar cell according to claim 1, wherein the front-side third silicon oxide layer has a refractive index of 1.4 or more.

15. The bifacial solar cell according to claim 1, wherein the front-side third silicon oxide layer has a thickness of 5 nm or more.

16. The bifacial solar cell according to claim 1, wherein the back-side silicon oxide layer has a refractive index of 1.4 or more.

17. The bifacial solar cell according to claim 1, wherein the back-side silicon oxide layer has a thickness of 5 nm or more.

18. The bifacial solar cell according to claim 1, wherein the back-side first nitrogen-containing silicon compound layer has a refractive index of 2.0 or more.

19. The bifacial solar cell according to claim 1, wherein the back-side first nitrogen-containing silicon compound layer has a thickness of 10 nm or more.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is an electroluminescence (EL) picture of a failed bifacial cell double-glass module after PID at a bias voltage of 1500 V in laboratory.

(2) FIG. 2 illustrates a PID failure model of a bifacial PERC cell.

(3) FIG. 3 is a structure diagram of a bifacial solar cell provided in Example 1.

REFERENCE LIST

(4) 1 silicon wafer having a PN junction 2 passivation layer 3 back-side silicon oxide layer 4 back-side first nitrogen-containing silicon compound layer 5 back-side second nitrogen-containing silicon compound layer 6 front-side first silicon oxide layer 7 front-side second silicon oxide layer 8 front-side first nitrogen-containing silicon compound layer 9 front-side second nitrogen-containing silicon compound layer 10 front-side third silicon oxide layer

(5) FIG. 4 is a flowchart of a method for preparing a bifacial solar cell provided in Example 1.

(6) FIG. 5(A) is an initial EL picture of a bifacial solar cell single-glass module provided in Example 1 in a test; FIG. 5(B) is an EL picture of Sample 1# of the bifacial solar cell single-glass module provided in Example 1 after 96 h of PID; FIG. 5(C) is an EL picture of Sample 1# of the bifacial solar cell single-glass module provided in Example 1 after 192 h of PID; and FIG. 5(D) is an EL picture of Sample 1# of the bifacial solar cell single-glass module provided in Example 1 after 288 h of PID.

(7) FIG. 6(A) is an initial EL picture of Sample 2# of the bifacial solar cell single-glass module provided in Example 1; FIG. 6(B) is an EL picture of Sample 2# of the bifacial solar cell single-glass module provided in Example 1 after 96 h of PID; FIG. 6(C) is an EL picture of Sample 2# of the bifacial solar cell single-glass module provided in Example 1 after 192 h of PID; and FIG. 6(D) is an EL picture of Sample 2# of the bifacial solar cell single-glass module provided in Example 1 after 288 h of PID.

(8) FIG. 7(A) is an initial EL picture of a bifacial solar cell double-glass module provided in Example 1; FIG. 7(B) is an EL picture of the bifacial solar cell double-glass module provided in Example 1 after 96 h of PID; FIG. 7(C) is an EL picture of the bifacial solar cell double-glass module provided in Example 1 after 192 h of PID; and FIG. 7(D) is an EL picture of the bifacial solar cell double-glass module provided in Example 1 after 288 h of PID.

DETAILED DESCRIPTION

(9) To better illustrate the present application and to facilitate the understanding of the technical solutions of the present application, the present application is further described in detail below. The examples described below are merely simple examples of the present application and not intended to represent or limit the scope of the present application. The scope of the present application is defined by the claims. Typical but non-limiting examples of the present application are described below.

Example 1

(10) This example provides a bifacial solar cell having a structure as shown in FIG. 3. The bifacial solar cell includes a silicon wafer 1 having a PN junction, and a front-side first silicon oxide layer 6, a front-side second silicon oxide layer 7, a front-side first nitrogen-containing silicon compound layer 8, a front-side second nitrogen-containing silicon compound layer 9 and a front-side third silicon oxide layer 10 that are located on the N-type side of the silicon wafer 1 having a PN junction and stacked in sequence in a direction away from the silicon wafer; a passivation layer 2, a back-side silicon oxide layer 3, a back-side first nitrogen-containing silicon compound layer 4 and a back-side second nitrogen-containing silicon compound layer 5 that are located on the P-type side of the silicon wafer 1 having a PN junction and stacked in sequence in the direction away from the silicon wafer. The bifacial solar cell further includes a silver electrode. A silver electrode on the N-type side of the silicon wafer 1 having a PN junction passes through the front-side first silicon oxide layer, the front-side second silicon oxide layer, the front-side first nitrogen-containing silicon compound layer, the front-side second nitrogen-containing silicon compound layer and the front-side third silicon oxide layer. A silver electrode on the P-type side of the silicon wafer 1 having a PN junction passes through the back-side silicon oxide layer, the back-side first nitrogen-containing silicon compound layer and the back-side second nitrogen-containing silicon compound layer.

(11) In this example, each of the front-side first silicon oxide layer 6, the front-side second silicon oxide layer 7, the front-side third silicon oxide layer 10 and the back-side silicon oxide layer 3 is a SiO.sub.2 layer, the front-side first silicon oxide layer 6 is a thermal silicon oxide layer, and the front-side second silicon oxide layer 7, the front-side third silicon oxide layer 10 and the back-side silicon oxide layer 3 are electrodeposited silicon oxide layers. The passivation layer 2 is an aluminum oxide layer (AlO.sub.x, x=1.5).

(12) In this example, the front-side first nitrogen-containing silicon compound layer is a SiN.sub.x1 layer (x1=4/3), and the back-side first nitrogen-containing silicon compound layer is also a SiN.sub.x1 layer (x1=4/3). The front-side second nitrogen-containing silicon compound layer 9 is a SiN.sub.x2/SiN.sub.x3/SiO.sub.xN.sub.y stacked structure (x2=4/3, x3=4/3, x=1, y=1) stacked in sequence in the direction away from the silicon wafer 1 having a PN junction. The back-side second nitrogen-containing silicon compound layer 5 is a SiN.sub.x2/SiN.sub.x3 stacked structure (x2=4/3, x3=4/3) stacked in sequence in the direction away from the silicon wafer 1 having a PN junction.

(13) In the bifacial solar cell provided in this example, the front-side second silicon oxide layer 7 has a refractive index of 1.45 and a thickness of 6 nm, the front-side first nitrogen-containing silicon compound layer 8 has a refractive index of 2.2 and a thickness of 20 nm; the front-side third silicon oxide layer 10 has a refractive index of 1.4 and a thickness of 5, the passivation layer 2 has a thickness of 10 nm; the back-side silicon oxide layer 3 has a refractive index of 1.45 and a thickness of 12 nm, and the back-side first nitrogen-containing silicon compound layer 4 has a refractive index of 2.2 and a thickness of 15 nm.

(14) This example further provides a method for preparing a bifacial solar cell. Specific steps are as follows: subjecting a P-type gallium-doped silicon wafer to front-line process (texturization, HF/HCl mixed acid cleaning, diffusion and front-side laser doping SE) to obtain a silicon wafer having a PN junction, growing a front-side first silicon oxide layer on the N-type side of the silicon wafer having a PN junction through a thermal oxidation method and performing a front-side growth, a back-side growth, back-side laser grooving, silver-electrode screen printing and sintering to obtain the bifacial solar cell. A flowchart of the method is shown in FIG. 4.

(15) A method of the back-side growth includes the steps described below.

(16) In (1) step, the silicon wafer after the thermal oxidation process was inserted into a graphite boat and sent into an inner tube of a tubular PECVD furnace through a mechanical arm, where a time was set to 110 s, a temperature was set to 320 C., a pressure was set to 10000 Pa, and a speed of sending the boat was set to 1000 mm/min.

(17) In (2) step, the mechanical arm was pulled from the furnace tube, the furnace tube was closed, and at the same time, a temperature was set to 320 C., and a vacuumizing test, a leak detection and a pressure maintaining test were performed.

(18) In (3) step, the system entered a constant temperature and constant pressure stage, where a time was set to 10 s, a temperature was set to 320 C., a pressure was set to 1500 Pa, and an introduced laughing gas flow was 5800 sccm.

(19) In (4) step, the system entered a deposition stage of aluminum oxide, where a time was set to 180 s, a temperature was set to 320 C., a pressure was set to 1500 Pa, an introduced laughing gas flow was 5800 sccm, an opening degree of trimethylaluminium (TMA) was 75%, a radio frequency power was 7000 W, and a pulse switch ratio was 20/1000.

(20) In (5) step, vacuumizing was performed to evacuate the remaining gas after the reaction, where a time was set to 50 s, a temperature was set to 480 C., and a pressure was set to 0 Pa.

(21) In (6) step, the system entered a second constant temperature and constant pressure stage, where a time was set to 10 s, a temperature was set to 480 C., a pressure was set to 900 Pa, an introduced ammonia flow was 2500 sccm, and an introduced laughing gas flow was 2500 sccm.

(22) In (7) step, an activation pretreatment process of aluminum oxide was performed, that is, partial ion implantation of H passivation was performed on the aluminum oxide grown in step (4), where a time was set to 350 s, a temperature was set to 480 C., a pressure was set to 900 Pa, an introduced ammonia flow was 2500 sccm, an introduced laughing gas flow was 2500 sccm, a radio frequency power was 3500 W, and a pulse switch ratio was 30/120.

(23) In (8) step, the system entered a growth stage of silicon oxide, where a time was set to 80 s, a temperature was set to 480 C., a pressure was set to 1500 Pa, an introduced silane flow was 650 sccm, an introduced laughing gas flow was 5200 sccm, a radio frequency power was 8000 W, and a pulse switch ratio was 36/1000.

(24) In (9) step, vacuumizing was performed to evacuate the remaining gas after the reaction, where a time was set to 300 s, a temperature was set to 480 C., and a pressure was set to 0 Pa.

(25) In (10) step, the system entered a third constant temperature and constant pressure stage, where a time was set to 10 s, a temperature was set to 480 C., a pressure was set to 1700 Pa, an introduced silane flow was 1250 sccm, and an introduced ammonia flow was 4880 sccm.

(26) In (11) step, the system entered a growth stage of a first SiN.sub.x1 layer having a high refractive index, where a time was set to 240 s, a temperature was set to 480 C., a pressure was set to 1700 Pa, an introduced silane flow was 1250 sccm, an introduced ammonia flow was 4880 sccm, a radio frequency power was 13000 W, and a pulse switch ratio was 50/700.

(27) In (12) step, the system entered a growth stage of a second SiN.sub.x2 layer, where a time was set to 130 s, a temperature was set to 480 C., a pressure was set to 1700 Pa, an introduced silane flow was 850 sccm, an introduced ammonia flow was 6000 sccm, a radio frequency power was 13000 W, and a pulse switch ratio was 50/600.

(28) In (13) step, the system entered a growth stage of a third SiN.sub.x3 layer, where a time was set to 130 s, a temperature was set to 480 C., a pressure was set to 1700 Pa, an introduced silane flow was 600 sccm, an introduced ammonia flow was 6500 sccm, a radio frequency power was 13000 W, and a pulse switch ratio was 50/600.

(29) In (14) step, after the process was completed, the system entered a stage of vacuumizing and filling with nitrogen back to normal pressure, where a time was set to 150 s, a temperature was set to 430 C., a pressure was set to 10000 Pa, and an introduced nitrogen flow was 40000 sccm.

(30) In (15) step, a door of the furnace was opened, and the boat was taken out to end the entire back-side PECVD film coating process, where a time was set to 110 s, a temperature was set to 430 C., a pressure was set to 10000 Pa, and a speed of taking out the boat was set to 1000 mm/min.

(31) A method of the front-side growth includes the steps described below.

(32) In (1) step, a boat was sent into a furnace, that is, the silicon wafer was placed on a graphite holder and sent into a tubular PECVD film coating device through a mechanical arm, where a time was set to 120 s, a temperature was set to 500 C., and a pressure was 10000 Pa.

(33) In (2) step, vacuumizing was performed, that is, vacuumizing was performed on a furnace tube for the first time, where a time was set to 200 s, a temperature was set to 500 C., and a pressure was 0 Pa.

(34) In (3) step, a leak detection was performed, that is, whether the vacuum had leak was tested, so as to ensure a process effect before a process gas was introduced, where a time was set to 20 s, a temperature was set to 500 C., and a pressure was 10000 Pa.

(35) In (4) step, vacuumizing was performed, that is, re-vacuumizing was rapidly performed on the furnace tube, where a time was set to 20 s, a temperature was set to 500 C., and a pressure was 0 Pa.

(36) In (5) step, the system entered a pressure equalizing stage, that is, the system was vacuumized to reach a set pressure, and a portion of the process gas was pre-introduced, where a time was set to 20 s, a temperature was set to 500 C., a pressure was 200 Pa, a silane flow was 985 sccm, and a laughing gas flow was 4620 sccm.

(37) In (6) step, silicon oxide was deposited, where a time was set to 80 s, a temperature was set to 500 C., a pressure was set to 200 Pa, an introduced silane flow was 985 sccm, an introduced laughing gas flow was 4620 sccm, a radio frequency power was 12600 W, and a pulse switch ratio was 5/150.

(38) In (7) step, vacuumizing was performed to pump an excess reaction gas to prepare for the next step, where a time was set to 20 s, a temperature was set to 500 C., and a pressure was 0 Pa.

(39) In (8) step, the system entered a pressure equalizing stage, that is, the system was vacuumized to reach a set pressure, and a portion of the process gas was pre-introduced, where a time was set to 20 s, a temperature was set to 500 C., a pressure was 230 Pa, a silane flow was 2200 sccm, and an ammonia flow was 6600 sccm.

(40) In (9) step, a first SiN.sub.x1 layer having a high refractive index was deposited, where a time was set to 65 s, a temperature was set to 500 C., a pressure was set to 230 Pa, an introduced silane flow was 2200 sccm, an introduced ammonia flow was 6600 sccm, a radio frequency power was 16500 W, and a pulse switch ratio was 5/80.

(41) In (10) step, in a stage of depositing a second SiN.sub.x2 layer, a time was set to 160 s, a temperature was set to 500 C., a pressure was set to 230 Pa, an introduced silane flow was 1000 sccm, an introduced ammonia flow was 12000 sccm, a radio frequency power was 17500 W, and a pulse switch ratio was 5/80.

(42) In (11) step, in a stage of depositing a third SiN.sub.x3 layer, a time was set to 250 s, a temperature was set to 500 C., a pressure was set to 230 Pa, an introduced silane flow was 800 sccm, an introduced ammonia flow was 12200 sccm, a radio frequency power was 17500 W, and a pulse switch ratio was 5/80.

(43) In (12) step, in a stage of depositing a SiO.sub.xN.sub.y layer, a time was set to 160 s, a temperature was set to 500 C., a pressure was set to 190 Pa, an introduced silane flow was 1000 sccm, an introduced ammonia flow was 2800 sccm, an introduced laughing gas flow was 7800 sccm, a radio frequency power was 17500 W, and a pulse switch ratio was 5/80.

(44) In (13) step, vacuumizing was performed to pump an excess reaction gas to prepare for the next step, where a time was set to 20 s, a temperature was set to 500 C., and a pressure was 0 Pa.

(45) In (14) step, the system entered a pressure equalizing stage, that is, the system was vacuumized to reach a set pressure, and a portion of the process gas was pre-introduced, where a time was set to 10 s, a temperature was set to 500 C., a pressure was 180 Pa, a silane flow was 600 sccm, and a laughing gas flow was 9600 sccm.

(46) In (15) step, an outermost silicon oxide layer was deposited, where a time was set to 180 s, a temperature was set to 500 C., a pressure was set to 180 Pa, an introduced silane flow was 600 sccm, an introduced laughing gas flow was 9600 sccm, a radio frequency power was 14500 W, and a pulse switch ratio was 5/150.

(47) In (16) step, vacuumizing was performed to pump an excess reaction gas, where a time was set to 25 s, a temperature was set to 500 C., and a pressure was 0 Pa.

(48) In (17) step, the furnace tube was cleaned, and a residual gas in the furnace was purged, where a time was set to 15 s, a temperature was set to 500 C., a pressure was 0 Pa, and a nitrogen flow was 25000 sccm.

(49) In (18) step, vacuumizing was performed to pump an excess reaction gas, where a time was set to 15 s, a temperature was set to 500 C., and a pressure was 0 Pa.

(50) In (19) step, the system was back to normal pressure to prepare for opening a door of the furnace, where a time was set to 90 s, a temperature was set to 500 C., a pressure was 10000 Pa, and a nitrogen flow was 50000 sccm.

(51) In (20) step, the door of the furnace was opened, and the graphite boat was taken out to end the entire front-side PECVD film coating process, where a time was set to 110 s, a temperature was set to 500 C., a pressure was set to 10000 Pa, and a speed of taking out the boat was set to 1000 mm/min.

(52) The bifacial solar cell provided in this example was prepared into a bifacial PERC cell single-glass module, which had a structure of front-plate glass/front-side EVA/cell sheet/back-side white EVA/white back-plate.

(53) Two samples (1# and 2#) were taken out from the above single-glass module for a PID test at a bias voltage of 1500 V. The test results are shown in the following table. A qualification criterion is as follows: the degradation of peak power after 96 h of PID is less than or equal to 3%, and each of the degradation of peak power after 192 h of PID and the degradation of peak power after 288 h of PID is less than or equal to 5%.

(54) TABLE-US-00001 TABLE 1 Short Open Degradation Fill Circuit Circuit Peak Peak Peak of Peak Whether PID/h Sample Factor/% Current/A Voltage/V Current/A Voltage/V Power/W Power/% Qualified 0 1# 79.37 11.357 49.54 10.864 41.11 446.60 0.00 / 96 79.19 11.258 49.33 10.771 40.83 439.78 1.53 qualified 192 79.12 11.236 49.40 10.759 40.82 439.14 1.67 qualified 288 79.01 11.240 49.29 10.748 40.72 437.67 2.00 qualified 0 2# 79.41 11.324 49.50 10.835 41.08 445.14 0.00 / 96 78.76 11.273 49.25 10.738 40.71 437.21 1.78 qualified 192 78.44 11.245 49.37 10.681 40.76 435.40 2.19 qualified 288 78.46 11.270 49.16 10.717 40.56 434.72 2.34 qualified

(55) As can be seen from the above table, after 288 h of the 1500 V bias voltage test, the power degradation of the single-glass module can still be maintained less than 2.5%.

(56) FIGS. 5(A) to 5(D) are EL pictures (EL refers to electroluminescence) of 1# at different times, respectively, and FIGS. 6(A) to 6(D) are EL pictures of 2# at different times, respectively. As can be seen from the above figures, from the beginning of the test to 288 h, no apparent failed dark sheet of the cell is seen in the EL pictures.

(57) The bifacial solar cell provided in this example was prepared into a bifacial PERC cell double-glass module, which had a structure of front-plate glass/high-transmittance EVA/cell sheet/transparent POE/back-plate glass.

(58) A sample (3#) was taken out from the above double-glass module for a PID test at a bias voltage of 1500 V. The test results are shown in the following table. A qualification criterion is as follows: the degradation of peak power after 96 h of PID is less than or equal to 3%, and each of the peak power degradation after 192 h of PID and the peak power degradation after 288 h of PID is less than or equal to 5%.

(59) TABLE-US-00002 TABLE 2 Short Open Degradation Fill Circuit Circuit Peak Peak Peak of Peak Whether PID/h Sample Factor/% Current/A Voltage/V Current/A Voltage/V Power/W Power/% Qualified 0 3# 79.32 11.396 49.55 10.876 41.19 447.94 0.00 / 96 79.14 11.345 49.42 10.829 40.98 443.71 0.94 qualified 192 78.98 11.349 49.48 10.819 40.99 443.48 1.00 qualified 288 79.06 11.336 49.47 10.829 40.94 443.35 1.03 qualified

(60) As can be seen from the above table, after 288 h of the 1500 V bias voltage test, the power degradation of the double-glass module can still be maintained about 1.0%.

(61) FIGS. 7(A) to 7(D) are EL pictures of 3# at different times, respectively. As can be seen from the above figures, from the beginning of the test to 288 h, no apparent failed dark sheet of the cell is seen in the EL pictures.

Example 2

(62) The structure and the material type of the bifacial solar cell provided in this example are the same as those in Example 1. Specific thickness parameters of the bifacial solar cell provided in this example are as follows: the front-side second silicon oxide layer 7 has a refractive index of 1.43 and a thickness of 7 nm; the front-side first nitrogen-containing silicon compound layer 8 has a refractive index of 2.1 and a thickness of 23 nm; the front-side third silicon oxide layer 10 has a refractive index of 1.4 and a thickness of 8; the passivation layer 2 has a thickness of 12 nm; the back-side silicon oxide layer 3 has a refractive index of 1.485 and a thickness of 12 nm; and the back-side first nitrogen-containing silicon compound layer 4 has a refractive index of 2.3 and a thickness of 18 nm.

(63) The preparation method of this example differs from Example 1 in that this example has the methods of the back-side growth and the front-side growth described below.

(64) The method of the back-side growth includes the steps described below.

(65) In (1) step, the silicon wafer after the thermal oxidation process was inserted into a graphite boat and sent into an inner tube of a tubular PECVD furnace through a mechanical arm, where a time was set to 110 s, a temperature was set to 310 C., a pressure was set to 10000 Pa, and a speed of sending the boat was set to 1000 mm/min.

(66) In (2) step, the mechanical arm was pulled from the furnace tube, the furnace tube was closed and at the same time, a temperature was set to 310 C., and a vacuumizing test, a leak detection and a pressure maintaining test were performed.

(67) In (3) step, the system entered a constant temperature and constant pressure stage, where a time was set to 10 s, a temperature was set to 310 C., a pressure was set to 1450 Pa, and an introduced laughing gas flow was 5800 sccm.

(68) In (4) step, the system entered a deposition stage of aluminum oxide, where a time was set to 170 s, a temperature was set to 310 C., a pressure was set to 1450 Pa, an introduced laughing gas flow was 5800 sccm, an opening degree of TMA was 75%, a radio frequency power was 7000 W, and a pulse switch ratio was 20/1000.

(69) In (5) step, vacuumizing was performed to evacuate the remaining gas after the reaction, where a time was set to 45 s, a temperature was set to 470 C., and a pressure was set to 0 Pa.

(70) In (6) step, the system entered a second constant temperature and constant pressure stage, where a time was set to 9 s, a temperature was set to 470 C., a pressure was set to 850 Pa, an introduced ammonia flow was 2500 sccm, and an introduced laughing gas flow was 2500 sccm.

(71) In (7) step, an activation pretreatment process of aluminum oxide was performed, that is, partial ion implantation of H passivation was performed on the aluminum oxide grown in step (4), where a time was set to 340 s, a temperature was set to 470 C., a pressure was set to 850 Pa, an introduced ammonia flow was 2500 sccm, an introduced laughing gas flow was 2500 sccm, a radio frequency power was 3500 W, and a pulse switch ratio was 30/120.

(72) In (8) step, the system entered a growth stage of silicon oxide, where a time was set to 75 s, a temperature was set to 470 C., a pressure was set to 1450 Pa, an introduced silane flow was 650 sccm, an introduced laughing gas flow was 5200 sccm, a radio frequency power was 8000 W, and a pulse switch ratio was 36/1000.

(73) In (9) step, vacuumizing was performed to evacuate the remaining gas after the reaction, where a time was set to 290 s, a temperature was set to 470 C., and a pressure was set to 0 Pa.

(74) In (10) step, the system entered a third constant temperature and constant pressure stage, where a time was set to 9 s, a temperature was set to 470 C., a pressure was set to 1650 Pa, an introduced silane flow was 1250 sccm, and an introduced ammonia flow was 4880 sccm.

(75) In (11) step, the system entered a growth stage of a first SiN.sub.x1 layer having a high refractive index, where a time was set to 235 s, a temperature was set to 470 C., a pressure was set to 1650 Pa, an introduced silane flow was 1250 sccm, an introduced ammonia flow was 4880 sccm, a radio frequency power was 13000 W, and a pulse switch ratio was 50/700.

(76) In (12) step, the system entered a growth stage of a second SiN.sub.x2 layer, where a time was set to 125 s, a temperature was set to 470 C., a pressure was set to 1650 Pa, an introduced silane flow was 850 sccm, an introduced ammonia flow was 6000 sccm, a radio frequency power was 13000 W, and a pulse switch ratio was 50/600.

(77) In (13) step, the system entered a growth stage of a third SiN.sub.x3 layer, where a time was set to 125 s, a temperature was set to 470 C., a pressure was set to 1650 Pa, an introduced silane flow was 600 sccm, an introduced ammonia flow was 6500 sccm, a radio frequency power was 13000 W, and a pulse switch ratio was 50/600.

(78) In (14) step, after the process was completed, the system entered a stage of vacuumizing and filling with nitrogen back to normal pressure, where a time was set to 150 s, a temperature was set to 430 C., a pressure was set to 10000 Pa, and an introduced nitrogen flow was 40000 sccm.

(79) In (15) step, a door of the furnace was opened, and the boat was taken out to end the entire back-side PECVD film coating process, where a time was set to 110 s, a temperature was set to 430 C., a pressure was set to 10000 Pa, and a speed of taking out the boat was set to 1000 mm/min.

(80) The method of the front-side growth includes the steps described below.

(81) In (1) step, a boat was sent into a furnace, that is, the silicon wafer was placed on a graphite holder and sent into a tubular PECVD film coating device through a mechanical arm, where a time was set to 120 s, a temperature was set to 4900 C., and a pressure was 10000 Pa.

(82) In (2) step, vacuumizing was performed, that is, vacuumizing was performed on a furnace tube for the first time, where a time was set to 200 s, a temperature was set to 490 C., and a pressure was 0 Pa.

(83) In (3) step, a leak detection was performed, that is, whether the vacuum had leak was tested, so as to ensure a process effect before a process gas was introduced, where a time was set to 20 s, a temperature was set to 490 C., and a pressure was 10000 Pa.

(84) In (4) step, vacuumizing was performed, that is, re-vacuumizing was rapidly performed on the furnace tube, where a time was set to 20 s, a temperature was set to 490 C., and a pressure was 0 Pa.

(85) In (5) step, the system entered a pressure equalizing stage, that is, the system was vacuumized to reach a set pressure, and a portion of the process gas was pre-introduced, where a time was set to 15 s, a temperature was set to 490 C., a pressure was 195 Pa, a silane flow was 985 sccm, and a laughing gas flow was 4620 sccm.

(86) In (6) step, silicon oxide was deposited, where a time was set to 75 s, a temperature was set to 450 C., a pressure was set to 195 Pa, an introduced silane flow was 985 sccm, an introduced laughing gas flow was 4620 sccm, a radio frequency power was 12600 W, and a pulse switch ratio was 5/150.

(87) In (7) step, vacuumizing was performed to pump an excess reaction gas to prepare for the next step, where a time was set to 15 s, a temperature was set to 500 C., and a pressure was 0 Pa.

(88) In (8) step, the system entered a pressure equalizing stage, that is, the system was vacuumized to reach a set pressure, and a portion of the process gas was pre-introduced, where a time was set to 15 s, a temperature was set to 490 C., a pressure was 225 Pa, a silane flow was 2200 sccm, and an ammonia flow was 6600 sccm.

(89) In (9) step, a first SiN.sub.x1 layer having a high refractive index was deposited, where a time was set to 60 s, a temperature was set to 450 C., a pressure was set to 225 Pa, an introduced silane flow was 2200 sccm, an introduced ammonia flow was 6600 sccm, a radio frequency power was 16500 W, and a pulse switch ratio was 5/80.

(90) In (10) step, in a stage of depositing a second SiN.sub.x2 layer, a time was set to 155 s, a temperature was set to 490 C., a pressure was set to 225 Pa, an introduced silane flow was 1000 sccm, an introduced ammonia flow was 12000 sccm, a radio frequency power was 17500 W, and a pulse switch ratio was 5/80.

(91) In (11) step, in a stage of depositing a third SiN.sub.x3 layer, a time was set to 240 s, a temperature was set to 490 C., a pressure was set to 225 Pa, an introduced silane flow was 800 sccm, an introduced ammonia flow was 12200 sccm, a radio frequency power was 17500 W, and a pulse switch ratio was 5/80.

(92) In (12) step, in a stage of depositing a SiO.sub.xN.sub.y layer, a time was set to 160 s, a temperature was set to 490 C., a pressure was set to 185 Pa, an introduced silane flow was 1000 sccm, an introduced ammonia flow was 2800 sccm, an introduced laughing gas flow was 7800 sccm, a radio frequency power was 17500 W, and a pulse switch ratio was 5/80.

(93) In (13) step, vacuumizing was performed to pump an excess reaction gas to prepare for the next step, where a time was set to 20 s, a temperature was set to 490 C., and a pressure was 0 Pa.

(94) In (14) step, the system entered a pressure equalizing stage, that is, the system was vacuumized to reach a set pressure, and a portion of the process gas was pre-introduced, where a time was set to 10 s, a temperature was set to 490 C., a pressure was 180 Pa, a silane flow was 600 sccm, and a laughing gas flow was 9600 sccm.

(95) In (15) step, an outermost silicon oxide layer was deposited, where a time was set to 175 s, a temperature was set to 490 C., a pressure was set to 175 Pa, an introduced silane flow was 600 sccm, an introduced laughing gas flow was 9600 sccm, a radio frequency power was 14500 W, and a pulse switch ratio was 5/150.

(96) In (16) step, vacuumizing was performed to pump an excess reaction gas, where a time was set to 25 s, a temperature was set to 490 C., and a pressure was 0 Pa.

(97) In (17) step, the furnace tube was cleaned, and a residual gas in the furnace was purged, where a time was set to 15 s, a temperature was set to 490 C., a pressure was 0 Pa, and a nitrogen flow was 25000 sccm.

(98) In (18) step, vacuumizing was performed to pump an excess reaction gas, where a time was set to 15 s, a temperature was set to 490 C., and a pressure was 0 Pa.

(99) In (19) step, the system was back to normal pressure to prepare for opening a door of the furnace, where a time was set to 90 s, a temperature was set to 490 C., a pressure was 10000 Pa, and a nitrogen flow was 50000 sccm.

(100) In (20) step, the door of the furnace was opened, and the graphite boat was taken out to end the entire front-side PECVD film coating process, where a time was set to 110 s, a temperature was set to 490 C., a pressure was set to 10000 Pa, and a speed of taking out the boat was set to 1000 mm/min.

(101) The bifacial solar cell provided in this example was prepared into a bifacial PERC cell single-glass module according to the method of Example 1, and a PID test was performed on this module according to the method of Example 1. The test results are described below.

(102) TABLE-US-00003 TABLE 3 Short Open Degradation Fill Circuit Circuit Peak Peak Peak of Peak Whether PID/h Factor/% Current/A Voltage/V Current/A Voltage/V Power/W Power/% Qualified 0 79.63 11.186 41.39 10.710 34.43 368.71 0.00 / 96 79.34 11.177 41.22 10.686 34.21 365.55 0.86 qualified 192 79.42 11.131 41.21 10.661 34.17 364.24 1.21 qualified

(103) The bifacial solar cell provided in this example was prepared into a bifacial PERC cell double-glass module according to the method of Example 1, and a PID test was performed on this module according to the method of Example 1. The test results are described below.

(104) TABLE-US-00004 TABLE 4 Short Open Fill Circuit Circuit Peak Peak Peak Degradation Factor/ Current/ Voltage/ Current/ Voltage/ Power/ of Peak Whether PID/h % A V A V W Power/% Qualified 0 79.47 11.180 41.41 10.702 34.37 367.88 0.00 / 96 79.25 11.171 41.27 10.679 34.22 365.39 0.68 qualified 192 79.17 11.145 41.24 10.657 34.15 363.93 1.07 qualified

Example 3

(105) The structure and the material type of the bifacial solar cell provided in this example are the same as those in Example 1. Specific thickness parameters of the bifacial solar cell provided in this example are as follows: the front-side second silicon oxide layer 7 has a refractive index of 1.48 and a thickness of 10 nm; the front-side first nitrogen-containing silicon compound layer 8 has a refractive index of 2.4 and a thickness of 20 nm; the front-side third silicon oxide layer 10 has a refractive index of 1.42 and a thickness of 8 nm; the passivation layer 2 has a thickness of 15 nm; the back-side silicon oxide layer 3 has a refractive index of 1.48 and a thickness of 15 nm; and the back-side first nitrogen-containing silicon compound layer 4 has a refractive index of 2.4 and a thickness of 20 nm.

(106) A method of the back-side growth includes the steps described below.

(107) In (1) step, the silicon wafer after the thermal oxidation process was inserted into a graphite boat and sent into an inner tube of a tubular PECVD furnace through a mechanical arm, where a time was set to 110 s, a temperature was set to 330 C., a pressure was set to 10000 Pa, and a speed of sending the boat was set to 1000 mm/min.

(108) In (2) step, the mechanical arm was pulled from the furnace tube, the furnace tube was closed and at the same time, a temperature was set to 330 C., and a vacuumizing test, a leak detection and a pressure maintaining test were performed.

(109) In (3) step, the system entered a constant temperature and constant pressure stage, where a time was set to 11 s, a temperature was set to 330 C., a pressure was set to 1550 Pa, and an introduced laughing gas flow was 5800 sccm.

(110) In (4) step, the system entered a deposition stage of aluminum oxide, where a time was set to 190 s, a temperature was set to 330 C., a pressure was set to 1550 Pa, an introduced laughing gas flow was 5800 sccm, an opening degree of TMA was 75%, a radio frequency power was 7000 W, and a pulse switch ratio was 20/1000.

(111) In (5) step, vacuumizing was performed to evacuate the remaining gas after the reaction, where a time was set to 50 s, a temperature was set to 490 C., and a pressure was set to 0 Pa.

(112) In (6) step, the system entered a second constant temperature and constant pressure stage, where a time was set to 11 s, a temperature was set to 490 C., a pressure was set to 950 Pa, an introduced ammonia flow was 2500 sccm, and an introduced laughing gas flow was 2500 sccm.

(113) In (7) step, an activation pretreatment process of aluminum oxide was performed, that is, partial ion implantation of H passivation was performed on the aluminum oxide grown in step (4), where a time was set to 360 s, a temperature was set to 490 C., a pressure was set to 950 Pa, an introduced ammonia flow was 2500 sccm, an introduced laughing gas flow was 2500 sccm, a radio frequency power was 3500 W, and a pulse switch ratio was 30/120.

(114) In (8) step, the system entered a growth stage of silicon oxide, where a time was set to 85 s, a temperature was set to 490 C., a pressure was set to 1550 Pa, an introduced silane flow was 650 sccm, an introduced laughing gas flow was 5200 sccm, a radio frequency power was 8000 W, and a pulse switch ratio was 36/1000.

(115) In (9) step, vacuumizing was performed to evacuate the remaining gas after the reaction, where a time was set to 300 s, a temperature was set to 490 C., and a pressure was set to 0 Pa.

(116) In (10) step, the system entered a third constant temperature and constant pressure stage, where a time was set to 11 s, a temperature was set to 490 C., a pressure was set to 1800 Pa, an introduced silane flow was 1250 sccm, and an introduced ammonia flow was 4880 sccm.

(117) In (11) step, the system entered a growth stage of a first SiN.sub.x1 layer having a high refractive index, where a time was set to 245 s, a temperature was set to 490 C., a pressure was set to 1750 Pa, an introduced silane flow was 1250 sccm, an introduced ammonia flow was 4880 sccm, a radio frequency power was 13000 W, and a pulse switch ratio was 50/700.

(118) In (12) step, the system entered a growth stage of a second SiN.sub.x2 layer, where a time was set to 135 s, a temperature was set to 490 C., a pressure was set to 1750 Pa, an introduced silane flow was 850 sccm, an introduced ammonia flow was 6000 sccm, a radio frequency power was 13000 W, and a pulse switch ratio was 50/600.

(119) In (13) step, the system entered a growth stage of a third SiN.sub.x3 layer, where a time was set to 135 s, a temperature was set to 490 C., a pressure was set to 1750 Pa, an introduced silane flow was 600 sccm, an introduced ammonia flow was 6500 sccm, a radio frequency power was 13000 W, and a pulse switch ratio was 50/600.

(120) In (14) step, after the process was completed, the system entered a stage of vacuumizing and filling with nitrogen back to normal pressure, where a time was set to 150 s, a temperature was set to 430 C., a pressure was set to 10000 Pa, and an introduced nitrogen flow was 40000 sccm.

(121) In (15) step, a door of the furnace was opened, and the boat was taken out to end the entire back-side PECVD film coating process, where a time was set to 110 s, a temperature was set to 430 C., a pressure was set to 10000 Pa, and a speed of taking out the boat was set to 1000 mm/min.

(122) A method of the front-side growth includes the steps described below.

(123) In (1) step, a boat was sent into a furnace, that is, the silicon wafer was placed on a graphite holder and sent into a tubular PECVD film coating device through a mechanical arm, where a time was set to 120 s, a temperature was set to 510 C., and a pressure was 10000 Pa.

(124) In (2) step, vacuumizing was performed, that is, vacuumizing was performed on a furnace tube for the first time, where a time was set to 200 s, a temperature was set to 510 C., and a pressure was 0 Pa.

(125) In (3) step, a leak detection was performed, that is, whether the vacuum had leak was tested, so as to ensure a process effect before a process gas was introduced, where a time was set to 20 s, a temperature was set to 510 C., and a pressure was 10000 Pa.

(126) In (4) step, vacuumizing was performed, that is, re-vacuumizing was rapidly performed on the furnace tube, where a time was set to 20 s, a temperature was set to 510 C., and a pressure was 0 Pa.

(127) In (5) step, the system entered a pressure equalizing stage, that is, the system was vacuumized to reach a set pressure, and a portion of the process gas was pre-introduced, where a time was set to 25 s, a temperature was set to 510 C., a pressure was 205 Pa, a silane flow was 985 sccm, and a laughing gas flow was 4620 sccm.

(128) In (6) step, silicon oxide was deposited, where a time was set to 85 s, a temperature was set to 510 C., a pressure was set to 205 Pa, an introduced silane flow was 985 sccm, an introduced laughing gas flow was 4620 sccm, a radio frequency power was 12600 W, and a pulse switch ratio was 5/150.

(129) In (7) step, vacuumizing was performed to pump an excess reaction gas to prepare for the next step, where a time was set to 25 s, a temperature was set to 510 C., and a pressure was 0 Pa.

(130) In (8) step, the system entered a pressure equalizing stage, that is, the system was vacuumized to reach a set pressure, and a portion of the process gas was pre-introduced, where a time was set to 25 s, a temperature was set to 510 C., a pressure was 235 Pa, a silane flow was 2200 sccm, and an ammonia flow was 6600 sccm.

(131) In (9) step, a first SiN.sub.x1 layer having a high refractive index was deposited, where a time was set to 70 s, a temperature was set to 510 C., a pressure was set to 235 Pa, an introduced silane flow was 2200 sccm, an introduced ammonia flow was 6600 sccm, a radio frequency power was 16500 W, and a pulse switch ratio was 5/80.

(132) In (10) step, in a stage of depositing a second SiN.sub.x2 layer, a time was set to 165 s, a temperature was set to 510 C., a pressure was set to 235 Pa, an introduced silane flow was 1000 sccm, an introduced ammonia flow was 12000 sccm, a radio frequency power was 17500 W, and a pulse switch ratio was 5/80.

(133) In (11) step, in a stage of depositing a third SiN.sub.x3 layer, a time was set to 260 s, a temperature was set to 510 C., a pressure was set to 235 Pa, an introduced silane flow was 800 sccm, an introduced ammonia flow was 12200 sccm, a radio frequency power was 17500 W, and a pulse switch ratio was 5/80.

(134) In (12) step, in a stage of depositing a SiO.sub.xN.sub.y layer, a time was set to 165 s, a temperature was set to 510 C., a pressure was set to 195 Pa, an introduced silane flow was 1000 sccm, an introduced ammonia flow was 2800 sccm, an introduced laughing gas flow was 7800 sccm, a radio frequency power was 17500 W, and a pulse switch ratio was 5/80.

(135) In (13) step, vacuumizing was performed to pump an excess reaction gas to prepare for the next step, where a time was set to 20 s, a temperature was set to 510 C., and a pressure was 0 Pa.

(136) In (14) step, the system entered a pressure equalizing stage, that is, the system was vacuumized to reach a set pressure, and a portion of the process gas was pre-introduced, where a time was set to 15 s, a temperature was set to 510 C., a pressure was 185 Pa, a silane flow was 600 sccm, and a laughing gas flow was 9600 sccm.

(137) In (15) step, an outermost silicon oxide layer was deposited, where a time was set to 185 s, a temperature was set to 510 C., a pressure was set to 185 Pa, an introduced silane flow was 600 sccm, an introduced laughing gas flow was 9600 sccm, a radio frequency power was 14500 W, and a pulse switch ratio was 5/150.

(138) In (16) step, vacuumizing was performed to pump an excess reaction gas, where a time was set to 25 s, a temperature was set to 510 C., and a pressure was 0 Pa.

(139) In (17) step, the furnace tube was cleaned, and a residual gas in the furnace was purged, where a time was set to 15 s, a temperature was set to 510 C., a pressure was 0 Pa, and a nitrogen flow was 25000 sccm.

(140) In (18) step, vacuumizing was performed to pump an excess reaction gas, where a time was set to 15 s, a temperature was set to 510 C., and a pressure was 0 Pa.

(141) In (19) step, the system was back to normal pressure to prepare for opening a door of the furnace, where a time was set to 90 s, a temperature was set to 510 C., a pressure was 10000 Pa, and a nitrogen flow was 50000 sccm.

(142) In (20) step, the door of the furnace was opened, and the graphite boat was taken out to end the entire front-side PECVD film coating process, where a time was set to 110 s, a temperature was set to 510 C., a pressure was set to 10000 Pa, and a speed of taking out the boat was set to 1000 mm/min.

(143) The bifacial solar cell provided in this example was prepared into a bifacial PERC cell single-glass module according to the method of Example 1, and a PID test was performed on this module according to the method of Example 1. The test results are described below.

(144) TABLE-US-00005 TABLE 5 Short Open Fill Circuit Circuit Peak Peak Peak Degradation Factor/ Current/ Voltage/ Current/ Voltage/ Power/ of Peak Whether PID/h % A V A V W Power/% Qualified 0 80.40 11.379 41.67 10.898 34.98 381.19 0.00 / 96 80.13 11.319 41.53 10.822 34.81 376.66 1.19 qualified 192 79.47 11.291 41.25 10.718 34.54 370.19 2.89 qualified

(145) The bifacial solar cell provided in this example was prepared into a bifacial PERC cell double-glass module according to the method of Example 1, and a PID test was performed on this module according to the method of Example 1. The test results are described below.

(146) TABLE-US-00006 TABLE 6 Short Open Fill Circuit Circuit Peak Peak Peak Degradation Factor/ Current/ Voltage/ Current/ Voltage/ Power/ of Peak Whether PID/h % A V A V W Power/% Qualified 0 80.39 11.412 41.82 10.930 35.10 383.68 0.00 / 96 79.85 11.358 41.65 10.842 34.84 377.71 1.56 qualified 192 78.96 11.345 41.45 10.701 34.70 371.33 3.22 qualified

Example 4

(147) The bifacial solar cell provided in this example differs from that in Example 1 only in that the back-side silicon oxide layer 3 has a refractive index of 1.2.

(148) The bifacial solar cell provided in this example was prepared into a bifacial PERC cell single-glass module according to the method of Example 1, and a PID test was performed on this module according to the method of Example 1. The test results are described below.

(149) TABLE-US-00007 TABLE 7 Short Open Fill Circuit Circuit Peak Peak Peak Degradation Factor/ Current/ Voltage/ Current/ Voltage/ Power/ of Peak Whether PID/h % A V A V W Power/% Qualified 0 80.22 11.481 41.78 10.976 35.05 384.74 0.00 / 96 79.21 11.409 41.53 10.806 34.73 375.31 2.45 qualified 192 75.26 11.395 41.13 10.363 34.04 352.75 8.31 unqualified

(150) The bifacial solar cell provided in this example was prepared into a bifacial PERC cell double-glass module according to the method of Example 1, and a PID test was performed on this module according to the method of Example 1. The test results are described below.

(151) TABLE-US-00008 TABLE 8 Short Open Fill Circuit Circuit Peak Peak Peak Degradation Factor/ Current/ Voltage/ Current/ Voltage/ Power/ of Peak Whether PID/h % A V A V W Power/% Qualified 0 79.45 10.938 41.28 10.464 34.29 358.80 0.00 / 96 78.05 10.568 39.66 10.053 32.53 327.08 8.84 unqualified 192 78.22 10.544 39.63 10.072 32.45 326.83 8.91 unqualified

Example 5

(152) The bifacial solar cell provided in this example differs from that in Example 1 only in that the back-side silicon oxide layer 3 has a thickness of 4 nm. The bifacial solar cell provided in this example was prepared into a bifacial PERC cell single-glass module according to the method of Example 1, and a PID test was performed on this module according to the method of Example 1. The test results are described below.

(153) TABLE-US-00009 TABLE 9 Short Open Fill Circuit Circuit Peak Peak Peak Degradation Factor/ Current/ Voltage/ Current/ Voltage/ Power/ of Peak Whether PID/h % A V A V W Power/% Qualified 0 80.31 11.460 41.81 10.969 35.08 384.79 0.00 / 96 79.66 11.398 41.55 10.847 34.78 377.28 1.95 qualified 192 78.13 11.380 41.30 10.660 34.45 367.18 4.58 unqualified

(154) The bifacial solar cell provided in this example was prepared into a bifacial PERC cell double-glass module according to the method of Example 1, and a PID test was performed on this module according to the method of Example 1. The test results are described below.

(155) TABLE-US-00010 TABLE 10 Short Open Fill Circuit Circuit Peak Peak Peak Degradation Factor/ Current/ Voltage/ Current/ Voltage/ Power/ of Peak Whether PID/h % A V A V W Power/% Qualified 0 79.49 10.953 41.26 10.476 34.29 359.24 0.00 / 96 78.77 10.543 39.77 10.105 32.68 330.26 8.07 unqualified 192 78.71 10.553 39.74 10.122 32.61 330.05 8.13 unqualified

Example 6

(156) The bifacial solar cell provided in this example differs from that in Example 1 only in that the back-side first nitrogen-containing silicon compound layer 4 has a refractive index of 1.8.

(157) The bifacial solar cell provided in this example was prepared into a bifacial PERC cell single-glass module according to the method of Example 1, and a PID test was performed on this module according to the method of Example 1. The test results are described below.

(158) TABLE-US-00011 TABLE 11 Short Open Fill Circuit Circuit Peak Peak Peak Degradation Factor/ Current/ Voltage/ Current/ Voltage/ Power/ of Peak Whether PID/h % A V A V W Power/% Qualified 0 80.39 11.412 41.82 10.930 35.10 383.68 0.00 / 96 79.85 11.358 41.65 10.842 34.84 377.71 1.56 qualified 192 78.94 11.299 41.13 10.675 34.37 366.87 4.38 unqualified

(159) The bifacial solar cell provided in this example was prepared into a bifacial PERC cell double-glass module according to the method of Example 1, and a PID test was performed on this module according to the method of Example 1. The test results are described below.

(160) TABLE-US-00012 TABLE 12 Short Open Fill Circuit Circuit Peak Peak Peak Degradation Factor/ Current/ Voltage/ Current/ Voltage/ Power/ of Peak Whether PID/h % A V A V W Power/% Qualified 0 79.56 10.935 41.27 10.468 34.30 359.05 0.00 / 96 78.32 10.460 39.29 9.986 32.23 321.87 10.36 unqualified 192 78.57 10.420 39.26 9.980 32.21 321.46 10.47 unqualified

Example 7

(161) The bifacial solar cell provided in this example differs from that in Example 1 only in that the back-side first nitrogen-containing silicon compound layer 4 has a thickness of 4 nm.

(162) The bifacial solar cell provided in this example was prepared into a bifacial PERC cell single-glass module according to the method of Example 1, and a PID test was performed on this module according to the method of Example 1. The test results are described below.

(163) TABLE-US-00013 TABLE 13 Short Open Fill Circuit Circuit Peak Peak Peak Degradation Factor/ Current/ Voltage/ Current/ Voltage/ Power/ of Peak Whether PID/h % A V A V W Power/% Qualified 0 80.32 11.444 41.69 10.962 34.95 374.20 0.00 / 96 78.46 11.368 41.27 10.683 34.46 363.25 2.93 qualified 192 77.90 11.299 41.03 10.594 34.09 353.85 5.74 unqualified

(164) The bifacial solar cell provided in this example was prepared into a bifacial PERC cell double-glass module according to the method of Example 1, and a PID test was performed on this module according to the method of Example 1. The test results are described below.

(165) TABLE-US-00014 TABLE 14 Short Open Fill Circuit Circuit Peak Peak Peak Degradation Factor/ Current/ Voltage/ Current/ Voltage/ Power/ of Peak Whether PID/h % A V A V W Power/% Qualified 0 79.63 10.954 41.29 10.480 34.37 360.19 0.00 / 96 78.32 10.476 39.35 9.979 32.35 322.81 10.38 unqualified 192 78.28 10.453 39.42 9.975 32.34 322.57 10.44 unqualified

Comparative Example 1

(166) The bifacial solar cell provided in this comparative example differs from that in Example 1 only in that the no back-side silicon oxide layer 3 is included.

(167) The bifacial solar cell provided in this example was prepared into a bifacial PERC cell single-glass module according to the method of Example 1, and a PID test was performed on this module according to the method of Example 1. The test results are described below.

(168) TABLE-US-00015 TABLE 15 Short Open Fill Circuit Circuit Peak Peak Peak Degradation Factor/ Current/ Voltage/ Current/ Voltage/ Power/ of Peak Whether PID/h % A V A V W Power/% Qualified 0 41.18 34.200 11.46 10.942 79.28 374.20 0.00 / 96 40.76 33.520 11.36 10.689 77.40 358.25 4.26 unqualified 192 40.76 33.520 11.27 10.556 77.06 353.85 5.44 unqualified

(169) The bifacial solar cell provided in this example was prepared into a bifacial PERC cell double-glass module according to the method of Example 1, and a PID test was performed on this module according to the method of Example 1. The test results are described below.

(170) TABLE-US-00016 TABLE 16 Short Open Fill Circuit Circuit Peak Peak Peak Degradation Factor/ Current/ Voltage/ Current/ Voltage/ Power/ of Peak Whether PID/h % A V A V W Power/% Qualified 0 40.95 33.850 11.36 10.818 78.73 366.18 0.00 / 96 40.21 32.940 11.15 10.604 77.89 349.23 4.63 unqualified 192 39.78 32.440 10.85 10.365 77.89 336.26 8.17 unqualified

Comparative Example 2

(171) The bifacial solar cell provided in this comparative example differs from that in Example 1 only in that the no back-side first nitrogen-containing silicon compound layer 4 is included.

(172) The bifacial solar cell provided in this example was prepared into a bifacial PERC cell single-glass module according to the method of Example 1, and a PID test was performed on this module according to the method of Example 1. The test results are described below.

(173) TABLE-US-00017 TABLE 17 Short Open Fill Circuit Circuit Peak Peak Peak Degradation Factor/ Current/ Voltage/ Current/ Voltage/ Power/ of Peak Whether PID/h % A V A V W Power/% Qualified 0 41.17 34.170 11.47 10.932 79.14 373.57 0.00 / 96 40.86 33.630 11.34 10.714 77.75 360.31 3.55 unqualified 192 40.80 33.500 11.27 10.467 76.24 350.65 6.14 unqualified

(174) The bifacial solar cell provided in this example was prepared into a bifacial PERC cell double-glass module according to the method of Example 1, and a PID test was performed on this module according to the method of Example 1. The test results are described below.

(175) TABLE-US-00018 TABLE 18 Short Open Fill Circuit Circuit Peak Peak Peak Degradation Factor/ Current/ Voltage/ Current/ Voltage/ Power/ of Peak Whether PID/h % A V A V W Power/% Qualified 0 40.93 33.830 11.37 10.832 78.73 366.46 0.00 / 96 40.22 33.010 11.16 10.623 78.11 350.72 4.30 unqualified 192 39.61 32.270 10.93 10.393 77.44 335.35 8.49 unqualified

(176) In view of the data of the preceding examples and comparative examples, it can be seen that the bifacial solar cells provided in Examples 1 to 3 each adopt a special design of a layered film structure (including a multilayer design of a front-side film and a multilayer design of a back-side film, where the back-side silicon oxide layer and the back-side first nitrogen-containing silicon compound layer are the most critical structures for solving back-side PID of the bifacial PERC cell), which enhances the compactness and electrical characteristics of a comprehensive film and can slow down an occurrence of the back-side PID very effectively.

(177) In Example 4, since the back-side silicon oxide layer 3 has a relatively low refractive index, the film is not compact enough, resulting in a damage to the passivation layer on the back side by Na.sup.+ ions.

(178) In Example 5, since the back-side silicon oxide layer 3 has a relatively low thickness, the film is relatively thin, which easily causes a damage to the passivation layer on the back side by Na.sup.+ ions.

(179) In Example 6, since the back-side first nitrogen-containing silicon compound layer 4 has a relatively low refractive index, the film is not compact enough, resulting in a damage to the passivation layer on the back side by Na.sup.+ ions.

(180) In Example 7, since the back-side first nitrogen-containing silicon compound layer 4 has a relatively low thickness, the film is relatively thin, which easily causes a damage to the passivation layer on the back side by Na.sup.+ ions.

(181) In Comparative Example 1, since the no back-side silicon oxide layer 3 is included, no protective film serves to block, resulting in a damage to the passivation layer on the back side by Na.sup.+ ions.

(182) In Comparative Example 2, since the no back-side first nitrogen-containing silicon compound layer 4 is included, no protective film serves to block, resulting in a damage to the passivation layer on the back side by Na.sup.+ ions.

(183) The applicant has stated that although the detailed method of the present application is described through the examples described above, the present application is not limited to the detailed method described above, which means that the implementation of the present application does not necessarily depend on the detailed method described above.