SOLID STATE HOLE TRANSPORT MATERIAL

Abstract

A solid or quasisolid state hole transport material (HTM) includes the following complex:

##STR00001##

in which M is copper (Cu), palladium (Pd), gold (Au), silver (Ag), nickel (Ni), vanadium (V) cobalt (Co); and each structure represents an at least 6,6′ disubstituted 2,2′-bipyridine, or an at least 2,9 disubstituted 1,10-phenanthroline Electronic devices, such as solar cells can include the solid or quasisolid state HTM, in which the complex is the main hole conducting compound of the HTM.

Claims

1. A solid or quasisolid state hole transport material (HTM) comprising the complex of Formula I: ##STR00009## wherein M is selected from copper (Cu), palladium (Pd), gold (Au), silver (Ag), nickel (Ni), vanadium (V) and cobalt (Co); and each structure ##STR00010## represents an at least 6,6′ disubstituted 2,2′-bipyridine, or an at least 2,9 disubstituted 1,10-phenanthroline, and wherein the complex of Formula I is a main hole conducting compound of the HTM.

2. The solid or quasisolid state HTM according to claim 1, wherein said complex of Formula I is represented by Formula II: ##STR00011## wherein each of R.sub.1, R.sub.8, R.sub.9, and R.sub.16 independently represents a group other than H, and each of R.sub.2-R.sub.7 and R.sub.10-R.sub.15 independently represents H.

3. The solid or quasisolid state HTM according to claim 1, wherein said complex of Formula I is represented by Formula III: ##STR00012## wherein each of R.sub.1, R.sub.8, R.sub.9, and R.sub.16 independently represents a group other than H, and each of R.sub.2-R.sub.7 and R.sub.10-R.sub.15 independently represents H.

4. The solid or quasisolid state HTM according to claim 2, wherein each of R.sub.1, R.sub.8, R.sub.9, and R.sub.16 independently is selected from the group consisting of substituted and non-substituted, branched and unbranched, alkyl and aryl groups.

5. The solid or quasisolid state HTM according to claim 1, wherein M is selected from Cu, Pd, Au, Ag and V.

6. The solid or quasisolid state HTM according to claim 2, wherein said complex of Formula II is M-(2,9-dimethyl-1,10-phenanthroline).sub.2.

7. The solid or quasisolid state HTM according to claim 3, wherein said complex of Formula III is M-(6,6′-dimethyl-2,2′-bipyridine).sub.2.

8. The solid or quasisolid state HTM according to claim 1, further comprising a negative counter ion selected from the group consisting of PF.sub.6.sup.− (hexafluorophosphate), TFSI.sup.− (bis(trifluoromethane) sulfonimide), Cl.sup.− (chloride) and BF.sup.− (tetrafluoroborate).

9. The solid or quasisolid state HTM according to claim 1, wherein said complex of Formula I is in a solid state.

10. An electronic device comprising the solid or quasisolid state hole transport material (HTM) according to claim 1.

11. The electronic device according to claim 10, wherein said device is an organic electronic device.

12. The electronic device according to claim 10, wherein said device is a solar cell including a hybrid solar cell, an organic solar cell, and a dye-sensitized solar cell (DSC).

13. The electronic device according to claim 10, wherein said device is a solid state dye-sensitized solar cell (ssDSC).

14. A method of producing an electronic device including a complex of Formula I: ##STR00013## wherein M is selected from copper (Cu), palladium (Pd), gold (Au), silver (Ag), nickel (Ni), vanadium (V) and cobalt (Co); and each structure ##STR00014## represents an at least 6,6′ disubstituted 2,2′-bipyridine, or an at least 2,9 disubstituted 1,10-phenanthroline, as a main hole transport material in a solid state electronic device.

15. The solid or quasisolid state HTM according to claim 2, wherein each of R.sub.1, R.sub.8, R.sub.9, and R.sub.16 independently is a lower alkyl.

16. The solid or quasisolid state HTM according to claim 2, wherein R.sub.1, R.sub.8, R.sub.9, and R.sub.16 are methyl.

17. The solid or quasisolid state HTM according to claim 1, wherein M is Cu.

18. The solid or quasisolid state HTM according to claim 2, wherein said complex of Formula II is Cu-(2,9-dimethyl-1,10-phenanthroline).sub.2.

19. The solid or quasisolid state HTM according to claim 3, wherein said complex of Formula III is Cu-(6,6′-dimethyl-2,2′-bipyridine).sub.2.

20. The electronic device according to claim 10, wherein said device is an organic light emitting diode (OLED) or an organic transistor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings, wherein:

[0051] FIG. 1 is a schematic cross-sectional representation of the structures of the example solar cells (device A and B) according to the present invention. Device A comprises a metal contact (1), a conducting layer (2), a HTM (3), a photosensitizer/perovskite (4), a blocking layer (5) a FTO layer (6), and a glass/substrate (7). Device B has a sandwich structure of a glass/substrate (7), a FTO layer (6), a conducting layer (2), a HTM (3), a photosensitizer/perovskite (4), polymer/spacer (8), a blocking layer (5), a FTO layer (6), and a glass/substrate (7).

[0052] FIG. 2 is a diagram showing the current density vs. voltage characteristics (J-V characteristics) of DSCs comprising HTMs and liquid electrolytes of copper dimethyl phenanthroline, copper dimethybipyridine and Spiro-OMeTAD under irradiation of 100 mW cm.sup.−2 simulated AM 1.5 sunlight.

DETAILED DESCRIPTION

Examples

Example 1: Synthesis of Cudmp.SUB.2

[0053] All chemicals and solvents were purchased from Sigma-Aldrich, if not stated otherwise, and were used without further purification.

Cu(II)dmp.sub.2Cl.sub.2 (1):

[0054] One equivalent of CuCl.sub.2 was mixed with 4 equivalents of Neocuproine hydrate in ethanol, under nitrogen atmosphere, at room temperature for 2 hours. Complex (1) was collected by filtration and washed with water and diethyl ether. The yield was 80% (mol).

Cu(II)dmp.SUB.2.Cl-TFSI (2):

[0055] Complex (1) was dissolved in a 1:2 ethanol/water mixture. To this solution, 5 equivalents of Li-TFSI were added. The solution was stirred for 2 hours at room temperature under nitrogen atmosphere. Complex (2) was collected by filtration and washed with water and diethyl ether. The yield was 92% (mol).

Cu(I)dmp.SUB.2.TFSI (3):

[0056] Complex (2) was dissolved in acetonitrile. To this solution, 10 equivalents of ascorbic acid were added. The solution was stirred for 2 hours at room temperature under nitrogen atmosphere in diethyl ether. After filtration of the remaining ascorbic acid, the solvent was evaporated which provided complex (3) as a crude of dark red powder. After further purification, complex (3) was obtained as intense red powder. The yield was 90% (mol).

##STR00006## ##STR00007##

Synthetic Procedure for Copper (I/II) Phenanthroline Complexes (Cu(Dmp).SUB.2

Example 2: Synthesis of Cudmbp.SUB.2

[0057] All chemicals and solvents were purchased from Sigma-Aldrich, if not stated otherwise, and were used without further purification.

Cu(II)dmbp.sub.2Cl.sub.2 (4):

[0058] One equivalent of CuCl.sub.2 was mixed with 2.2 equivalents of 2,2′-dimethyl bipyridine in ethanol and water (1:1), under nitrogen atmosphere, at room temperature for 2 hours. Complex (4) was collected by filtration and washed with water and diethyl ether. The yield was 80% (mol).

Cu(II)dmp.SUB.2.Cl-TFSI (5):

[0059] Complex (4) was dissolved in 1:2 ethanol/water mixture. To this solution, 5 equivalents of Li-TFSI were added. The solution was stirred for 2 hours at room temperature under nitrogen atmosphere. Complex (5) was collected by filtration and washed with water and diethyl ether. The yield was 92% (mol).

Cu(I)dmbp.SUB.2.TFSI (6):

[0060] Complex (5) was dissolved in acetonitrile. To this solution, 10 equivalents of ascorbic acid were added. The solution was stirred for 2 hours at room temperature under nitrogen amosphere. After filtration of the remaining ascorbic acid, the solvent was evaporated which provided the crude of complex (6) as a dark red powder. After further purification complex (6) was obtained as intense red powder. The yield was 60% (mol).

##STR00008##

Synthetic Procedure for Copper (I/II) Dimethyl Bipyridine Complexes (Cu(dmbp).SUB.2.)

Example 3: Preparation of ssDSC Devices

[0061] A ssDSC device is fabricated using metal oxide nanoparticles with attached photosensitizer or perovskite layer as the absorber layer, see FIG. 1 (Device A and B).

[0062] Briefly, a blocking layer (100-200 nm) is deposited on top of a transparent conducting oxide (FTO) layer to prevent ohmic contact between the HTM and FTO. Next, a metal oxide layer (for example in the form of nanoparticles, nanotubes, nanowires, etc) is deposited on top of the blocking layer. Subsequent to deposition, the metal oxide substrate is treated with a photosensitizer or a perovskite layer to afford a layer of absorber material along the surface of the metal oxide. Preferred metal oxide materials are TiO.sub.2, SnO.sub.2, ZnO, Sb.sub.2O.sub.3, PbO, Nb.sub.2O.sub.5, ZrO.sub.3, CeO.sub.2, WO.sub.3, SiO.sub.2, Al.sub.2O.sub.3, CuAlO.sub.2, SrTiO.sub.3, SrCu.sub.2O.sub.2 or a complex oxide containing several of these oxides. Next, an HTM as described herein is applied to the metal oxide/photosensitizer. The sensitized TiO.sub.2 film is coated with a constant thickness layer of HTM, which can be applied by vapour deposition, or by solution process deposition, for example spin-coating or spray-coating of a HTM solution, followed by drying.

[0063] Then a conducting buffer layer of poly(3,4-ethylenedioxythiophene) (PEDOT) or graphite and a metal layer (Ag, Au, Al, Ca or Mg) is deposited on top of the HTM to complete the device (Device A) or with electrodeposited PEDOT on FTO Glass substrate with thermoplastic polymer (e.g. Surlyn) as spacer in a sandwich arrangement (Device B).

Example 4: Preparation of ssDSC Prototypes Based on Spiro-OMeTAD, Cudmp.SUB.2 .and Cudmbp.SUB.2 .as HTMs

[0064] In this Example, an HTM composition including Cudmp.sub.2 or Cudmbp.sub.2 (Cu(I) 0.2 M and Cu(II) 0.05 M), 4-tert-butylpyridine (TBP, 0.5 M), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI 0.1 M) in a mixture of chlorobenzene (CB) or acetonitrile (CH.sub.3CN) was used. The different HTMs/electrolytes used are listed below in Table 1.

[0065] Each of the HTM compositions was dispersed onto TiO.sub.2 nanoparticle substrates that had previously been soaked in a solution of photosensitizer (0.2 mM, LEG 4 in tert-butanol and acetonitrile). Following (Device B) a deposition of PEDOT/FTO (aq. Electrodepostion of PEDOT) electrode on top by melting Surlyn as a spacer.

TABLE-US-00001 TABLE 1 Tested HTM/electrolyte and structure of device No. HTM/Electrolyte Device A/B 1 Cudmbp.sub.2 HTM B 2 Cudmbp.sub.2 EL B 3 Cudmp.sub.2 HTM B 4 Cudmp.sub.2 EL B 5 Spiro-OMeTAD B

[0066] The photocurrent density-voltage (J-V) characteristics of the DSCs and ssDSCs with the solid state HTMs and liquid electrolytes of copper dimethyl phenanthroline, copper dimethybipyridine and Spiro-OMeTAD were subsequently tested under 100 m W cm.sup.−2 AM 1.5 illumination. The detailed photovoltaic parameters of the open circuit voltage (V.sub.∝), fill factor (FF), short-circuit current density (J.sub.SC) and photovoltaic conversion efficiency (q) are given in Table 2 as well as in FIG. 2.

TABLE-US-00002 TABLE 2 J-V characteristics of DSCs and ssDSCs No. HTM/Electrolyte V.sub.oc (mV) J.sub.sc (mA/cm2) FF η (%) 1 Cudmbp.sub.2 HTM 995 11.8 0.63 7.4 2 Cudmbp.sub.2 EL 915 6.3 0.69 4.0 3 Cudmp.sub.2 HTM 1010 9.4 0.62 6.8 4 Cudmp.sub.2 EL 1010 6.6 0.67 4.5 5 Spiro-OMeTAD 895 9.4 0.67 5.6

[0067] As demonstrated in Table 2 above, use of copper dimethylphenanthroline or dimethylbipyridine as solid state HTMs improved the photocurrent density. The J.sub.SC of the DSC Cudmp.sub.2 and Cudmbp.sub.2 increased from 6.6 mA cm.sup.−2 to 9.4 mA cm.sup.−2 and 6.3 mA cm.sup.−2 to 11.8 mA cm.sup.−2 respectively, when Cudmp.sub.2 and Cudmbp.sub.2 were used as HTMs in ssDSC. Thus, the solid state HTMs show improvement both over the corresponding liquid HTMs and over Spiro-OMeTAD.