METHOD FOR MANUFACTURING A MULTI-CATION PEROVSKITE LAYER

Abstract

A method for manufacturing a multi-cation perovskite layer, including: a) supply of a substrate having a deposition face, b) deposition of a precursor solution including precursors comprising CsX, FAY, PbZ.sub.2, with X, Y and Z = I, Br, and an FAC1 additive, the molar ratio of cesium to lead is between approximately 4 % and 22%, the molar ratio of FAC1 relative to lead between 0.1% and 5%, and the perovskite layer has an empirical formula of the type Cs.sub.xFA(.sub.1-x+w)Pb(I.sub.yBr(.sub.1-y)).sub.3 with x between 0.04 and 0.22, y between 0 and 1 and w between 0.001 and 0.05, c) sweeping of the wet film by an inert gas to crystallize the perovskite layer, and heat treatment so that the deposition face has a temperature ranging from about 25° C. to 80° C. C at least during step b).

Claims

1. A method for manufacturing a layer of perovskite with multi-cations, with a view to form a photo-active layer, the method comprising the steps of: a) suppling a substrate having a deposition face, b) depositing a precursor solution comprising at least one solvent and perovskite precursors so as to form a wet film on the deposition face, the depositing being carried out by slot die coating or via a blade coating, the precursors comprising at least CsX, FAY, PbZ.sub.2, with X, Y and Z = I, Br, and an FACl additive, the amounts being determined such that the molar ratio of cesium to lead is comprised between about 4% and 22%, preferably between 13% and 20 %, that the molar ratio of FACl relative to lead is comprised between 0.1% and 5%, in particular between 0.1% and 2%, and that the perovskite layer has a empirical formula of the Cs.sub.xFA(.sub.1-x+w)Pb(I.sub.yBr(.sub.1-y)).sub.3 type with x comprised between 0.04 and 0.22, y comprised between 0 and 1 and w comprised between 0.001 and 0.05, and c) sweeping an exposed surface of the wet film by a flow of dry air or inert gas having a speed greater than or equal to 120 m/s so as to crystallize the multi-cations perovskite layer, the method further comprising the application of a heat treatment to the substrate so that the deposition face has a temperature ranging from about 25° C. to 80° C. at least during step b).

2. The manufacturing method according to claim 1, wherein the application of a heat treatment to the substrate is carried out so that the deposition face has a temperature ranging between about 30° C. and 70° C.

3. The manufacturing method according to claim 1, wherein the precursors of the perovskite layer are selected from a combination of CsX, FAY and PbZ.sub.2, with X, Y and Z = I, Br and the FACl additive.

4. The manufacturing method according to claim 1, wherein the at least one solvent is selected from DMF and/or DMSO.

5. The manufacturing method according to claim 1, wherein the molar concentration of lead in the precursor solution is comprised between 0.5 M and 1.7 M.

6. The manufacturing method according to claim 1, wherein the only thermal budget applied during the manufacturing method is provided by the heat treatment applied to the substrate so that the deposition face has a temperature ranging from about 25° C. to 80° C. during steps b) and c).

7. The manufacturing method according to claim 1, wherein step c) of applying the flow of inert gas or dry air is followed by a step d) of applying a thermal annealing carried out at a temperature comprised between 70° C. and 100° C.

8. The manufacturing method according to claim 1, wherein step c) of sweeping with a flow of inert gas or dry air is carried out by a relative displacement of the substrate comprising the wet film and a projection nozzle, such as a projection nozzle of a gas knife, the projection nozzle being arranged such that the length of the flow path of the inert gas or dry air between the outlet of the projection nozzle and the exposed surface of the wet film is comprised between about 3.1 millimeters and 6 millimeters.

9. The manufacturing method according to claim 8, wherein the speed of relative movement between the wet and the projection nozzle (6) during step c) is comprised between 1 and 50 mm/s.

10. The manufacturing method according to claim 8, wherein the angle α formed between the flow of inert gas or dry air and the wet film is comprised between 90° and 45°.

11. The manufacturing method according to claim 1, wherein step b) of depositing the precursor solution is carried out so as to obtain a constant wet film thickness comprised between 2 and 16 micrometers.

Description

[0064] The invention will be better understood on reading the non-limiting description which follows, made with reference to the appended figures.

[0065] [FIG. 1] is a schematic view illustrating steps a) to b) of an embodiment of the method of the invention.

[0066] [FIG. 2] is a schematic view illustrating steps b) and c) of the method of the invention.

[0067] [FIG. 3] is a schematic view illustrating step c) of the method of the invention.

[0068] [FIG. 4] is a schematic view of the outlet of a gas flow projection nozzle according to step c) of the method of the invention.

[0069] [FIG. 5] is a schematic view of an inclined projection nozzle according to step c) of the method of the invention.

[0070] [FIG. 6] is a schematic view of an architecture of the structure for a NIP-type solar cell formed from a layer of perovskite 100 manufactured according to an embodiment of the method of the invention.

[0071] [FIG. 7] is a view of an X-ray diffraction (XRD) analysis of the structure for NIP type solar cell without FACI additive.

[0072] [FIG. 8] is an XRD view of the structure for a NIP-type solar cell comprising a 0.1% molar ratio of FACI relative to lead according to one embodiment of the method of the invention.

[0073] [FIG. 9] is a view of an XRD analysis of the structure for a NIP-type solar cell comprising a 0.5% molar ratio of FACI relative to lead according to one embodiment of the method of the invention.

[0074] [FIG. 10] is a view of a XRD analysis of the structure for PIN-type solar cell without FACI additive.

[0075] [FIG. 11] is a view of an XRD analysis of the structure for a PIN-type solar cell comprising a 0.1% molar ratio of FACI relative to lead according to one embodiment of the method of the invention.

[0076] [FIG. 12] is a view of an XRD analysis of the structure for a PIN-type solar cell comprising a 0.5% molar ratio of FACI relative to lead according to one embodiment of the method of the invention.

[0077] In the following examples, the Pbl.sub.2 used is 99.99% pure and comes from TCI Chemicals (Japan), the PbBr.sub.2, FAI, Csl, FACI, DMF and DMSO come from Sigma Aldrich.

[0078] The used gas knife is the Silent X-Stream Air Blade equipment, available from AirFlow supplier.

[0079] The slot die coating is carried out using the Automatic-Research TFC 300 equipment.

[0080] The blade coating is carried out using a Zehntner ZUA 2000 deposition blade.

[0081] In these examples described below, the substrate 1 and the deposition face 2 are immobile but according to a particular arrangement, the substrate 1 and therefore the deposition face 2 moves while the device for depositing the wet film (blade coating) and the gas flow projection device (gas knife) are immobile (case of the flexible substrate in rolled form).

First Example Embodiment of the Method for Manufacturing a Layer of Crystalline Perovskite 100 According to the Invention by Blade Coating

[0082] The steps of the method are illustrated in FIGS. 1 to 3. FIG. 1 illustrates step a) of the method consisting in supplying a substrate 1 including a deposition face 2 on a heating platform 3 in a controlled-atmosphere enclosure (temperature about 21° C. and a relative humidity about 20%). Within the framework of the preparation of photovoltaic devices, the substrate 1 used is a structure (5 cm×5 cm) consisting of a glass support 7 (thickness 1.1 mm), covered with a layer of ITO 8 (layer of indium and tin oxide with a thickness about 220 nm) itself covered with a layer of SnO.sub.2 9 (tin oxide) prepared with a view to manufacture a NIP-type solar cell (illustrated in FIG. 6). Typically, the SnO.sub.2 layer was deposited beforehand by spin coating or slot-die coating then dried at 80° C. for one minute. It has a thickness about 50 nm and its roughness is about 5 nm.

[0083] A substrate 1 consisting of a PIN type solar cell structure can also be used, as can a substrate 1 making it possible to manufacture a tandem type structure using silicon. In the case of a PIN-type architecture, a self-assembled monolayer of 2-Pacz (or [2-(9H-Carbazol-9-yl)ethyl] phosphonic Acid supplied by the company TCI America - CAS number: 20999- 38-6) forms the holes extracting layer 11. This layer 11 is deposited by spin-coating on the ITO glass substrate previously treated with UV-ozone.

[0084] A heat treatment is applied via the heating platform 3 to the substrate 1 through the face opposite the deposition face 2. This heat treatment is controlled so that the temperature of the deposition face 2 of the substrate 1 is maintained at approximately 40° C.

[0085] A precursor solution is prepared from the following quantities of precursors Pbl.sub.2, (3.707 g), PbBr.sub.2 (1.453 g), FAI (1.631 g), Csl (0.468 g) and the FACI additive (9.7 mg), dissolved in 12 ml of a solvent mixture consisting of 10.8 ml of DMF and a 1.2 ml of DMSO. The concentration of Pb in the solution is about 1 M, the molar ratio of Cs to Pb is about 15% and the molar ratio of FACI to Pb is about 0.1%.

[0086] After stirring the precursor solution at 40° C. for approximately 12 hours, the deposition is carried out by a ‘blade coating’ device on a deposition face 2 of the substrate 1 having a temperature about 40° C. The distance between the spreading blade 4 of the blade coating device and the deposition face 2 of the substrate 1 is approximately 70 micrometers. The relative speed between the deposition face 2 and the spreading blade 4 is 20 mm/s and the volume of ink used is 20 microliters. The nitrogen flow is applied to the exposed surface of the wet film 5 with a speed about 137 m/s. The nitrogen flow projection nozzle 6 is arranged so that the length L of the gas flow path is approximately 3.6 mm. The nozzle 6 moves at a speed of 5 mm/s.

[0087] The projection nozzle 6 is oriented so that the nitrogen flow is sprayed by forming an angle αof 50° with the exposed surface of the wet film 5. According to a step d) (not shown) of the method, a heat treatment for a duration of 5 minutes at a temperature of 100° C. under an inert atmosphere is carried out after the passage of the projection nozzle. A layer of crystalline perovskite 100 with the molecular formula Cs.sub.0.15FA.sub.0.79Pb(l.sub.0.78Br.sub.0.22).sub.2.94 is obtained with high quality (the precision concerning the values of the molecular formula is limited to two decimal places).

[0088] Extended annealing tests were also carried out, with a total annealing time of 60 minutes at 100° C., still under an inert atmosphere.

Second Example Embodiment of the Method for Manufacturing a Layer of Crystalline Perovskite 100 According to the Invention by Blade Coating

[0089] In this second example, the precursor solution has the following quantities of precursors Pbl.sub.2, (3.707 g), PbBr.sub.2 (1.453 g), FAI (1.631 g), Csl (0.468 g) and FACI (48.3 mg) dissolved in 12 ml of a mixture consisting of 10.8 ml of DMF and 1.2 ml of DMSO. The concentration of Pb in the solution is about 1 M, the molar ratio of Cs to Pb is about 15% and the molar ratio of FACI to Pb is about 0.5%.

[0090] The other parameters described for the first example embodiment are identical for this second example embodiment.

[0091] Although this is not described in the examples, the deposition of the precursor solution by slot die coating is a possible deposition route.

Analyzes and Measurements Carried Out From the Layers of Perovskites Formed According to the Manufacturing Method of the Invention

[0092] Different layers of perovskite 100 were fabricated by a blade coating device for FACl/Pb molar ratios of 0.1 and 0.5% in NIP architecture (FIGS. 8 and 9) and PIN architecture (FIGS. 11 and 12) (the other elements remaining unchanged). The same analyzes were also carried out on layers prepared from a precursor solution not containing the FACI additive, and therefore serve as a reference (FIG. 7 for the NIP and FIG. 10 for the PIN).

[0093] The XRD (acronym for X-Ray Diffraction) analyzes of the formed layers show that a layer of polycrystalline perovskite 100 (alpha phase, or so-called black phase) is indeed present whether at 0.1 or 0.5% molar ratio of FACI with a total absence of a delta phase (or so-called yellow phase, which is not desired).

[0094] Moreover, a rate of 0.5% of the FACI additive makes it possible to limit or even eliminate the appearance of the signal relating to Pbl.sub.2 (between 12.5° and 13°) whether in NIP or PIN architecture (refer to FIGS. 9 or 12) while this signal is indeed present for the reference solution (FIGS. 7 or 10) and for the solution comprising an FACl/Pb molar ratio of 0.1%, the Pbl.sub.2 peak is moreover increased with an extended annealing 60 minutes at 100° C. (not shown). Interestingly, for this FACI level of 0.5%, the peak relating to Pbl.sub.2 is also not observed after prolonged annealing (total duration of 60 minutes - not shown).

Implementation of the Perovskite Layers Prepared According to the Invention in Solar Cells

So Called N-I-P Configuration

[0095] The perovskite 100 layers prepared as previously described are deposited on substrates 1 comprising a glass support 7, an ITO layer 8 (transparent electrode)/a SnO.sub.2 layer 9 (electron extracting layer) in a square shape of 5 cm x 5 cm. In order to complete the manufacture of the device, a holes extracting layer 11 of doped PTAA is deposited by spin coating on the perovskite layer 100, then an upper gold electrode 12 is evaporated in surface (refer to the stack in FIG. 6).

So Called P-I-N Configuration

[0096] In this other configuration, the perovskite layers prepared as previously described above are deposited on substrates comprising a glass support, a layer of ITO (transparent electrode) / a self-assembled monolayer of 2-PACz (or [2-(9H-Carbazol-9-yl) ethyl] phosphonic Acid supplied by the company TCI America - CAS number: 20999-38-6) forming the holes extracting layer, in the square shape of 5 cm x 5 cm. In order to complete the manufacture of the device, an electron extracting layer of C.sub.60 then a layer of BCP (or Bathocuproine, derivative of 1,10-phenanthroline, supplied by Sigma Aldrich - CAS number 4733-39-5) and an upper silver electrode are surface evaporated.

[0097] The photovoltaic performances of the 200 solar cells were measured at 25° C. under standard lighting conditions (1000 W.m-2, AM 1.5 G) with a Newport brand solar simulator. Current-voltage curves were recorded using a Keithley. The results are recorded in Table 1 below.

[0098] The first line of Table 1 reports the results obtained for a perovskite layer deposited by the Dr Blade method in NIP architecture without the FACI additive and serves as a reference. The results of the first example embodiment of a perovskite layer 100 with additive (Dr Blade coating as previously described) in NIP architecture are recorded in the second line of Table 1. These devices were prepared in the form of modules comprising 8 strips connected in series with a total active area of 10 cm.sup.2.

[0099] The third line of Table 1 shows the results obtained from cells 200 prepared in PIN architecture without the FACI additive and serves as a reference. The results of producing a layer of perovskite 100 with additive (Dr Blade coating as previously described) in PIN architecture are given in the fourth line of Table 1. These devices were prepared in the form of unit cells with a surface area of 33 mm.sup.2.

TABLE-US-00001 Deposit conditions V.sub.oc (mV) J.sub.sc (mA.cm.sup.-2) FF (%) PCE (%) Deposit by blade coating .sup.(2) (1 M in Pb — Cs/Pb 15%) NIP Architecture Reference Without Additive 9280 2.54 69.4 16.4 Deposit by blade coating.sup.(2) (1 M in Pb — Cs/Pb 15%) NIP Architecture With FACI Additive 0.5% 9635 2.44 77.5 18.2 Deposit by blade coating.sup.(1) (1 M in Pb — Cs/Pb 15%) PIN Architecture Reference Without Additive 1028 19.5 67.4 13.5 Deposit by blade coating.sup.(1) (1 M in Pb — Cs/Pb 15%) ( PIN Architecture With FACI Additive 0.5% 1073 20.8 66.2 14.8 .sup.(1) Best result obtained for cells prepared in the form of unit cells with an area of 33 mm.sup.2 .sup.(2) Best result obtained for cells prepared in the form of modules comprising 8 strips connected in series.

[0100] On reading the table, it can be seen that the performance of the solar cells 200 is increased for the perovskite layer obtained with the FACI additive. The presence of the additive makes it possible in particular to significantly improve the Voc whether in NIP or PIN configuration. Thus, the layers of perovskite 100 obtained according to the method of the present invention are of high quality and can be implemented in very efficient perovskite solar cells.

[0101] In conclusion, the invention makes it possible to optimize the manufacturing method of a layer of perovskite 100 with multi-cations. It makes it possible to form a quality crystalline layer 100, under conditions suitable for an industrial solution. The integration of these layers in devices of the solar cell type 200 is possible and leads to very good results.