WO2004025675A1 - Process for preparing nano-porous metal oxide semiconductor layers - Google Patents
Process for preparing nano-porous metal oxide semiconductor layers Download PDFInfo
- Publication number
- WO2004025675A1 WO2004025675A1 PCT/EP2002/010270 EP0210270W WO2004025675A1 WO 2004025675 A1 WO2004025675 A1 WO 2004025675A1 EP 0210270 W EP0210270 W EP 0210270W WO 2004025675 A1 WO2004025675 A1 WO 2004025675A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- nano
- metal oxide
- oxide semiconductor
- particles
- layer
- Prior art date
Links
- 239000004065 semiconductor Substances 0.000 title claims abstract description 75
- 229910044991 metal oxide Inorganic materials 0.000 title claims abstract description 59
- 150000004706 metal oxides Chemical class 0.000 title claims abstract description 59
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 14
- 238000000034 method Methods 0.000 claims abstract description 64
- 230000008569 process Effects 0.000 claims abstract description 56
- 239000006185 dispersion Substances 0.000 claims abstract description 51
- 239000002105 nanoparticle Substances 0.000 claims abstract description 38
- 238000000576 coating method Methods 0.000 claims abstract description 21
- 239000011248 coating agent Substances 0.000 claims abstract description 20
- 238000001556 precipitation Methods 0.000 claims abstract description 16
- 238000010438 heat treatment Methods 0.000 claims abstract description 13
- 238000005245 sintering Methods 0.000 claims description 21
- 239000000975 dye Substances 0.000 claims description 17
- 239000002245 particle Substances 0.000 claims description 17
- 230000003595 spectral effect Effects 0.000 claims description 6
- 235000014692 zinc oxide Nutrition 0.000 claims description 5
- 150000004770 chalcogenides Chemical class 0.000 claims description 4
- 229910052751 metal Inorganic materials 0.000 claims description 4
- 239000002184 metal Substances 0.000 claims description 4
- SOQBVABWOPYFQZ-UHFFFAOYSA-N oxygen(2-);titanium(4+) Chemical class [O-2].[O-2].[Ti+4] SOQBVABWOPYFQZ-UHFFFAOYSA-N 0.000 claims description 4
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 claims description 3
- 229910000484 niobium oxide Inorganic materials 0.000 claims description 2
- URLJKFSTXLNXLG-UHFFFAOYSA-N niobium(5+);oxygen(2-) Chemical class [O-2].[O-2].[O-2].[O-2].[O-2].[Nb+5].[Nb+5] URLJKFSTXLNXLG-UHFFFAOYSA-N 0.000 claims description 2
- VVRQVWSVLMGPRN-UHFFFAOYSA-N oxotungsten Chemical class [W]=O VVRQVWSVLMGPRN-UHFFFAOYSA-N 0.000 claims description 2
- BPUBBGLMJRNUCC-UHFFFAOYSA-N oxygen(2-);tantalum(5+) Chemical class [O-2].[O-2].[O-2].[O-2].[O-2].[Ta+5].[Ta+5] BPUBBGLMJRNUCC-UHFFFAOYSA-N 0.000 claims description 2
- 229910001936 tantalum oxide Inorganic materials 0.000 claims description 2
- 229910001887 tin oxide Inorganic materials 0.000 claims description 2
- QHGNHLZPVBIIPX-UHFFFAOYSA-N tin(ii) oxide Chemical class [Sn]=O QHGNHLZPVBIIPX-UHFFFAOYSA-N 0.000 claims description 2
- 229910001930 tungsten oxide Inorganic materials 0.000 claims description 2
- RNWHGQJWIACOKP-UHFFFAOYSA-N zinc;oxygen(2-) Chemical class [O-2].[Zn+2] RNWHGQJWIACOKP-UHFFFAOYSA-N 0.000 claims description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 105
- 239000004408 titanium dioxide Substances 0.000 description 48
- 210000004027 cell Anatomy 0.000 description 37
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 11
- 229910052707 ruthenium Inorganic materials 0.000 description 11
- WEVYAHXRMPXWCK-UHFFFAOYSA-N Acetonitrile Chemical compound CC#N WEVYAHXRMPXWCK-UHFFFAOYSA-N 0.000 description 9
- 239000004020 conductor Substances 0.000 description 9
- 239000011521 glass Substances 0.000 description 9
- 230000001235 sensitizing effect Effects 0.000 description 9
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 8
- 239000000463 material Substances 0.000 description 8
- -1 poly(styrene sulphonic acid) Polymers 0.000 description 7
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- XOLBLPGZBRYERU-UHFFFAOYSA-N SnO2 Inorganic materials O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 5
- 230000001172 regenerating effect Effects 0.000 description 5
- 239000007787 solid Substances 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- 239000000758 substrate Substances 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 229910052980 cadmium sulfide Inorganic materials 0.000 description 4
- UHYPYGJEEGLRJD-UHFFFAOYSA-N cadmium(2+);selenium(2-) Chemical compound [Se-2].[Cd+2] UHYPYGJEEGLRJD-UHFFFAOYSA-N 0.000 description 4
- 229920001609 Poly(3,4-ethylenedioxythiophene) Polymers 0.000 description 3
- 206010070834 Sensitisation Diseases 0.000 description 3
- 239000012298 atmosphere Substances 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 239000003792 electrolyte Substances 0.000 description 3
- 125000001810 isothiocyanato group Chemical group *N=C=S 0.000 description 3
- 239000011244 liquid electrolyte Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 230000008313 sensitization Effects 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 229910004613 CdTe Inorganic materials 0.000 description 2
- 229910004262 HgTe Inorganic materials 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- 229920003182 Surlyn® Polymers 0.000 description 2
- 239000005035 Surlyn® Substances 0.000 description 2
- 239000006096 absorbing agent Substances 0.000 description 2
- 229910052946 acanthite Inorganic materials 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 229910052798 chalcogen Inorganic materials 0.000 description 2
- 150000001787 chalcogens Chemical class 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 239000000084 colloidal system Substances 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- PDZKZMQQDCHTNF-UHFFFAOYSA-M copper(1+);thiocyanate Chemical group [Cu+].[S-]C#N PDZKZMQQDCHTNF-UHFFFAOYSA-M 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 230000001419 dependent effect Effects 0.000 description 2
- 230000005611 electricity Effects 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 239000011245 gel electrolyte Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 239000005340 laminated glass Substances 0.000 description 2
- 239000002650 laminated plastic Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 229910052976 metal sulfide Inorganic materials 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- ZKATWMILCYLAPD-UHFFFAOYSA-N niobium pentoxide Inorganic materials O=[Nb](=O)O[Nb](=O)=O ZKATWMILCYLAPD-UHFFFAOYSA-N 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- 230000037361 pathway Effects 0.000 description 2
- 230000000243 photosynthetic effect Effects 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 229920003023 plastic Polymers 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 239000002096 quantum dot Substances 0.000 description 2
- 238000005215 recombination Methods 0.000 description 2
- 230000006798 recombination Effects 0.000 description 2
- 238000006479 redox reaction Methods 0.000 description 2
- YAYGSLOSTXKUBW-UHFFFAOYSA-N ruthenium(2+) Chemical compound [Ru+2] YAYGSLOSTXKUBW-UHFFFAOYSA-N 0.000 description 2
- FSJWWSXPIWGYKC-UHFFFAOYSA-M silver;silver;sulfanide Chemical compound [SH-].[Ag].[Ag+] FSJWWSXPIWGYKC-UHFFFAOYSA-M 0.000 description 2
- 239000011343 solid material Substances 0.000 description 2
- 229910052959 stibnite Inorganic materials 0.000 description 2
- 239000000375 suspending agent Substances 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- PBCFLUZVCVVTBY-UHFFFAOYSA-N tantalum pentoxide Inorganic materials O=[Ta](=O)O[Ta](=O)=O PBCFLUZVCVVTBY-UHFFFAOYSA-N 0.000 description 2
- CHEANNSDVJOIBS-MHZLTWQESA-N (3s)-3-cyclopropyl-3-[3-[[3-(5,5-dimethylcyclopenten-1-yl)-4-(2-fluoro-5-methoxyphenyl)phenyl]methoxy]phenyl]propanoic acid Chemical compound COC1=CC=C(F)C(C=2C(=CC(COC=3C=C(C=CC=3)[C@@H](CC(O)=O)C3CC3)=CC=2)C=2C(CCC=2)(C)C)=C1 CHEANNSDVJOIBS-MHZLTWQESA-N 0.000 description 1
- GKWLILHTTGWKLQ-UHFFFAOYSA-N 2,3-dihydrothieno[3,4-b][1,4]dioxine Chemical compound O1CCOC2=CSC=C21 GKWLILHTTGWKLQ-UHFFFAOYSA-N 0.000 description 1
- AGBXYHCHUYARJY-UHFFFAOYSA-N 2-phenylethenesulfonic acid Chemical compound OS(=O)(=O)C=CC1=CC=CC=C1 AGBXYHCHUYARJY-UHFFFAOYSA-N 0.000 description 1
- GWOGSJALVLHACY-UHFFFAOYSA-N 2-pyridin-2-ylpyridine;ruthenium Chemical compound [Ru].N1=CC=CC=C1C1=CC=CC=N1 GWOGSJALVLHACY-UHFFFAOYSA-N 0.000 description 1
- UUIMDJFBHNDZOW-UHFFFAOYSA-N 2-tert-butylpyridine Chemical compound CC(C)(C)C1=CC=CC=N1 UUIMDJFBHNDZOW-UHFFFAOYSA-N 0.000 description 1
- MARUHZGHZWCEQU-UHFFFAOYSA-N 5-phenyl-2h-tetrazole Chemical compound C1=CC=CC=C1C1=NNN=N1 MARUHZGHZWCEQU-UHFFFAOYSA-N 0.000 description 1
- SNFCXVRWFNAHQX-UHFFFAOYSA-N 9,9'-spirobi[fluorene] Chemical compound C12=CC=CC=C2C2=CC=CC=C2C21C1=CC=CC=C1C1=CC=CC=C21 SNFCXVRWFNAHQX-UHFFFAOYSA-N 0.000 description 1
- 241000124815 Barbus barbus Species 0.000 description 1
- 229920002284 Cellulose triacetate Polymers 0.000 description 1
- 229910000673 Indium arsenide Inorganic materials 0.000 description 1
- 239000004952 Polyamide Substances 0.000 description 1
- 239000004642 Polyimide Substances 0.000 description 1
- 239000004793 Polystyrene Substances 0.000 description 1
- 235000002492 Rungia klossii Nutrition 0.000 description 1
- 244000117054 Rungia klossii Species 0.000 description 1
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 239000005864 Sulphur Substances 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 239000007983 Tris buffer Substances 0.000 description 1
- NNLVGZFZQQXQNW-ADJNRHBOSA-N [(2r,3r,4s,5r,6s)-4,5-diacetyloxy-3-[(2s,3r,4s,5r,6r)-3,4,5-triacetyloxy-6-(acetyloxymethyl)oxan-2-yl]oxy-6-[(2r,3r,4s,5r,6s)-4,5,6-triacetyloxy-2-(acetyloxymethyl)oxan-3-yl]oxyoxan-2-yl]methyl acetate Chemical compound O([C@@H]1O[C@@H]([C@H]([C@H](OC(C)=O)[C@H]1OC(C)=O)O[C@H]1[C@@H]([C@@H](OC(C)=O)[C@H](OC(C)=O)[C@@H](COC(C)=O)O1)OC(C)=O)COC(=O)C)[C@@H]1[C@@H](COC(C)=O)O[C@@H](OC(C)=O)[C@H](OC(C)=O)[C@H]1OC(C)=O NNLVGZFZQQXQNW-ADJNRHBOSA-N 0.000 description 1
- 238000002835 absorbance Methods 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 229910021417 amorphous silicon Inorganic materials 0.000 description 1
- 125000000129 anionic group Chemical group 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 238000003491 array Methods 0.000 description 1
- CJOBVZJTOIVNNF-UHFFFAOYSA-N cadmium sulfide Chemical compound [Cd]=S CJOBVZJTOIVNNF-UHFFFAOYSA-N 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 239000002800 charge carrier Substances 0.000 description 1
- 238000001246 colloidal dispersion Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000009770 conventional sintering Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- BWFPGXWASODCHM-UHFFFAOYSA-N copper monosulfide Chemical compound [Cu]=S BWFPGXWASODCHM-UHFFFAOYSA-N 0.000 description 1
- 238000007766 curtain coating Methods 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- DHCWLIOIJZJFJE-UHFFFAOYSA-L dichlororuthenium Chemical compound Cl[Ru]Cl DHCWLIOIJZJFJE-UHFFFAOYSA-L 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 238000007606 doctor blade method Methods 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- UHPJWJRERDJHOJ-UHFFFAOYSA-N ethene;naphthalene-1-carboxylic acid Chemical compound C=C.C1=CC=C2C(C(=O)O)=CC=CC2=C1 UHPJWJRERDJHOJ-UHFFFAOYSA-N 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
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- 239000010408 film Substances 0.000 description 1
- 229910052949 galena Inorganic materials 0.000 description 1
- 238000005286 illumination Methods 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- RPQDHPTXJYYUPQ-UHFFFAOYSA-N indium arsenide Chemical compound [In]#[As] RPQDHPTXJYYUPQ-UHFFFAOYSA-N 0.000 description 1
- AKUCEXGLFUSJCD-UHFFFAOYSA-N indium(3+);selenium(2-) Chemical compound [Se-2].[Se-2].[Se-2].[In+3].[In+3] AKUCEXGLFUSJCD-UHFFFAOYSA-N 0.000 description 1
- SIXIBASSFIFHDK-UHFFFAOYSA-N indium(3+);trisulfide Chemical compound [S-2].[S-2].[S-2].[In+3].[In+3] SIXIBASSFIFHDK-UHFFFAOYSA-N 0.000 description 1
- 238000007641 inkjet printing Methods 0.000 description 1
- 238000005305 interferometry Methods 0.000 description 1
- 125000001261 isocyanato group Chemical group *N=C=O 0.000 description 1
- XCAUINMIESBTBL-UHFFFAOYSA-N lead(ii) sulfide Chemical compound [Pb]=S XCAUINMIESBTBL-UHFFFAOYSA-N 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
- DZVCFNFOPIZQKX-LTHRDKTGSA-M merocyanine Chemical compound [Na+].O=C1N(CCCC)C(=O)N(CCCC)C(=O)C1=C\C=C\C=C/1N(CCCS([O-])(=O)=O)C2=CC=CC=C2O\1 DZVCFNFOPIZQKX-LTHRDKTGSA-M 0.000 description 1
- 229910001507 metal halide Inorganic materials 0.000 description 1
- 150000005309 metal halides Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- KRTSDMXIXPKRQR-AATRIKPKSA-N monocrotophos Chemical compound CNC(=O)\C=C(/C)OP(=O)(OC)OC KRTSDMXIXPKRQR-AATRIKPKSA-N 0.000 description 1
- 239000002159 nanocrystal Substances 0.000 description 1
- 239000010955 niobium Substances 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 210000001916 photosynthetic cell Anatomy 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229910052699 polonium Inorganic materials 0.000 description 1
- HZEBHPIOVYHPMT-UHFFFAOYSA-N polonium atom Chemical compound [Po] HZEBHPIOVYHPMT-UHFFFAOYSA-N 0.000 description 1
- 229920003227 poly(N-vinyl carbazole) Polymers 0.000 description 1
- 229920000058 polyacrylate Polymers 0.000 description 1
- 229920002647 polyamide Polymers 0.000 description 1
- 229920000515 polycarbonate Polymers 0.000 description 1
- 239000004417 polycarbonate Substances 0.000 description 1
- 229920000139 polyethylene terephthalate Polymers 0.000 description 1
- 239000005020 polyethylene terephthalate Substances 0.000 description 1
- 229920001721 polyimide Polymers 0.000 description 1
- 229920000098 polyolefin Polymers 0.000 description 1
- 229920002223 polystyrene Polymers 0.000 description 1
- 229920000915 polyvinyl chloride Polymers 0.000 description 1
- 239000004800 polyvinyl chloride Substances 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
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- IRPLSAGFWHCJIQ-UHFFFAOYSA-N selanylidenecopper Chemical compound [Se]=[Cu] IRPLSAGFWHCJIQ-UHFFFAOYSA-N 0.000 description 1
- 150000004771 selenides Chemical class 0.000 description 1
- 229910052711 selenium Inorganic materials 0.000 description 1
- 239000011669 selenium Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 241000894007 species Species 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- YPMOSINXXHVZIL-UHFFFAOYSA-N sulfanylideneantimony Chemical compound [Sb]=S YPMOSINXXHVZIL-UHFFFAOYSA-N 0.000 description 1
- RBWFXUOHBJGAMO-UHFFFAOYSA-N sulfanylidenebismuth Chemical compound [Bi]=S RBWFXUOHBJGAMO-UHFFFAOYSA-N 0.000 description 1
- PGWMQVQLSMAHHO-UHFFFAOYSA-N sulfanylidenesilver Chemical compound [Ag]=S PGWMQVQLSMAHHO-UHFFFAOYSA-N 0.000 description 1
- 229910052714 tellurium Inorganic materials 0.000 description 1
- PORWMNRCUJJQNO-UHFFFAOYSA-N tellurium atom Chemical compound [Te] PORWMNRCUJJQNO-UHFFFAOYSA-N 0.000 description 1
- DZLFLBLQUQXARW-UHFFFAOYSA-N tetrabutylammonium Chemical compound CCCC[N+](CCCC)(CCCC)CCCC DZLFLBLQUQXARW-UHFFFAOYSA-N 0.000 description 1
- 238000007669 thermal treatment Methods 0.000 description 1
- ANRHNWWPFJCPAZ-UHFFFAOYSA-M thionine Chemical compound [Cl-].C1=CC(N)=CC2=[S+]C3=CC(N)=CC=C3N=C21 ANRHNWWPFJCPAZ-UHFFFAOYSA-M 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 150000003627 tricarboxylic acid derivatives Chemical class 0.000 description 1
- ODHXBMXNKOYIBV-UHFFFAOYSA-N triphenylamine Chemical class C1=CC=CC=C1N(C=1C=CC=CC=1)C1=CC=CC=C1 ODHXBMXNKOYIBV-UHFFFAOYSA-N 0.000 description 1
- 238000007704 wet chemistry method Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/20—Light-sensitive devices
- H01G9/2027—Light-sensitive devices comprising an oxide semiconductor electrode
- H01G9/2031—Light-sensitive devices comprising an oxide semiconductor electrode comprising titanium oxide, e.g. TiO2
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/20—Light-sensitive devices
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/542—Dye sensitized solar cells
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/549—Organic PV cells
Definitions
- the present invention relates to a process for preparing nano- porous metal oxide semiconductor layers .
- the first type is the regenerative cell which converts light to electrical power leaving no net chemical change behind. Photons of energy exceeding that of the band gap generate electron- hole pairs, which are separated by the electrical field present in the space-charge layer. The negative charge carriers move through the bulk of the semiconductor to the current collector and the external circuit. The positive holes are driven to the surface where they are scavenged by the reduced form of the redox relay molecular (R) , oxidizing it: h * + R —» 0, the oxidized form. 0 is reduced back to R by the electrons that re-enter the cell from the external circuit.
- R redox relay molecular
- photosynthetic cells operate on a similar principle except that there are two redox systems: one reacting with the holes at the surface of the semiconductor electrode and the second reacting with the electrons entering the counter-electrode.
- water is typically oxidized to oxygen at the semiconductor photoanode and reduced to hydrogen at the cathode. Titanium dioxide has been the favoured semiconductor for these studies.
- Mesoscopic or nano-porous semiconductor materials minutely structured materials with an enormous internal surface area, have been developed for the first type of cell to improve the light capturing efficiency by increasing the area upon which the spectrally sensitizing species could adsorb.
- Arrays of nano- crystals of oxides such as Ti0 2 , ZnO, Sn0 2 and Nb 2 O s or chalcogenides such as CdSe are the preferred semiconductor materials and are interconnected to allow electrical conduction to take place.
- a wet type solar cell having a porous film of dye-sensitized titanium dioxide semiconductor particles as a work electrode was expected to surpass an amorphous silicon solar cell in conversion efficiency and cost.
- EP-A 1 176 646 discloses a solid state p-n heterojunction comprising an electron conductor and a hole conductor, characterized in that if further comprises a sensitizing semiconductor, said sensitizing being located at an interface between said electron conductor and said hole conductor; and its application in a solid state sensitized photovolaic cell.
- a drawback in the manufacture of nano-porous metal oxide semiconductor layers for Graetzel photovoltaic cells is the high temperature needed for making the nano-porous metal oxide semiconductor layer. This is apparently needed to obtain sufficient contact between the nano-porous metal oxide particles to create a conductive pathway for the photogenerated charges (electrons) .
- the term sintering is not the appropriate one in this context, this term is often used to describe this heating process. Usually temperatures between 300 and 550°C are applied for 15 to 90 minutes . Such high temperatures are prohibitive for making photovoltaic cells on plastic and flexible substrates. Such cells would offer a myriad of advantages for this type of photovoltaic cell.
- WO 00/72373 discloses a method for manufacturing a nanostructured porous film electrode, the method characterized by the steps of: preparing a binder-free suspension (21) of electrode material particles (11) in a volatile suspending agent (13), said particles substantially having a size within the nanometer scale, depositing the binder-free particle suspension (21) on a substrate (22) covered with a conducting film, removing the suspending agent (31) by evaporation, and compressing the particles to form an electrically conducting and mechanically stable nanostructured porous film.
- the process of WO 00/72373 enables the realization of the same solar cell performance with high pressure sintered nano- porous titanium dioxide layers as with conventional high temperature sintering. This finding was confirmed in 2000 by Pichot et al .
- layers of nano-porous metal oxide semiconductors can be prepared with nano-particles prepared by a wet precipitation process on supports by a process involving preheating the nano-particles at a temperature of 250 to 600°C, applying a coating of these preheated nano-particles to the support and subjecting the coating to a pressure of 100 to 1000 bar, without the application of the high temperatures needed for conventional sintering of titanium dioxide nano-particles i.e. 300 to 550°C.
- aspects of the present invention are realized by a process for preparing a layer of a nano-porous metal oxide semiconductor comprising the steps of: (i) providing metal oxide semiconductor nano-particles prepared by a wet precipitation process, (ii) heating said nano-particles at a temperature in the range of 250 to 600°C, (iii) preparing a dispersion of the heat-treated nano- particles from step (ii) , (iv) applying the dispersion of step (iii) to a support to produce a coating; and (v) subjecting said coating to a pressure in the range of 100 to 1000 bar at a temperature below 250°C.
- An electrically conducting and mechanically stable nano-porous metal oxide semiconductor layer is thereby prepared.
- aspects of the present invention are also realized by a layer of a nano-porous metal oxide semiconductor obtainable by the above- mentioned process.
- a photovoltaic device comprising a layer of a nano-porous metal oxide semiconductor obtainable by the above-mentioned process.
- nano-porous metal oxide semiconductor means a metal oxide semiconductor having pores with a size of 100 nm or less and having an internal surface area of at least 5 m 2 /g and not more than 300 m7g.
- chalcogenide means a binary compound containing a chalcogen and a more electropositive element or radical.
- a chalcogen is an element from group IV of the periodic table including oxygen, sulphur, selenium, tellurium and polonium.
- support means a "self-supporting material” so as to distinguish it from a “layer” which may be coated on a support, but which is itself not self-supporting. It also includes any treatment necessary for, or layer applied to aid, adhesion to the support.
- continuous layer refers to a layer in a single plane covering the whole area of the support and not necessarily in direct contact with the support.
- non-continuous layer refers to a layer in a single plane not covering the whole area of the support and not necessarily in direct contact with the support.
- coating is used as a generic term including all means of applying a layer including all techniques for producing continuous layers, such as curtain coating, doctor-blade coating etc., and all techniques for producing non-continuous layers such as screen printing, ink jet printing, flexographic printing, and techniques for producing continuous layers.
- PEDOT represents poly (3 , 4-ethylenedioxy- thiophene) .
- PSS poly(styrene sulphonic acid) or poly (styrenesulphonate) .
- a process for preparing a layer of a nano-porous metal oxide semiconductor comprising the steps of: (i) providing metal oxide semiconductor nano-particles prepared by a wet precipitation process, (ii) heating said nano-particles at a temperature in the range of 250 to 600°C, (iii) preparing a dispersion of the heat-treated nano- particles from step (ii) , (iv) applying the dispersion of step (iii) to a support to produce a coating; and (v) subjecting said coating to a pressure in the range of 100 to 1000 bar at a temperature below 250°C.
- the metal oxide semiconductor is n-type.
- the nano-porous metal oxide semiconductor has a band-gap of greater than 2.9 eV.
- the nano-porous metal oxide semiconductor nano-particle have a mean number averaged particle size ⁇ 20 run.
- the nano-porous metal oxide semiconductor is selected from the group consisting of titanium oxides, tin oxides, niobium oxides, tantalum oxides, tungsten oxides and zinc oxides.
- the nano-porous metal oxide semiconductor is titanium dioxide.
- the nano-porous metal oxide semiconductor is titanium dioxide and between 80 and 100% thereof has an anatase morphology.
- the nano-porous metal oxide semiconductor is titanium dioxide and between 90 and 100% thereof has an anatase morphology.
- the pretreatment temperature is in the range of 300 to 500°C.
- the pretreatment temperature is in the range of 350 to 450°C.
- the sintering pressure is in the range of 300 to 700 bar. According to an eleventh embodiment of the process, according to the present invention, the sintering pressure is in the range of 400 to 600 bar.
- the process further comprises heating the coating subjected to pressure from step (v) at a temperature of 100 to 200°C.
- the process further comprises heating the coating subjected to pressure from step (v) at a temperature of 125 to 170°C.
- step (v) is carried out at a temperature above 0°C.
- Step (ii) of the process, according to the present invention is carried out under the atmosphere and pressure necessary to obtain metal oxide nano-particles with semiconducting properties.
- step (ii) is carried out at under an ambient atmosphere i.e. at the pertaining ambient pressure and under the pertaining ambient atmosphere.
- the sintering pressure for a particular layer of a nano-porous metal oxide semiconductor is dependent upon the nature of the support, a sintering pressure of 300 to 700 bar being suitable for glass supports and sintering pressures up to 1000 bar being suitable for polymeric film supports.
- the coating of the nano-porous Ti02 should be between 8 and 12 ⁇ m in order to have sufficient light absorption for generating power conversion efficiencies up to 5 to 8%.
- the thicker the titanium dioxide coating the longer the pathway for the charges (electrons) have to be transported to the charge collecting electrode and the greater the probability of recombination occurring with resultant power conversion efficiency loss.
- smaller titanium dioxide nano-particles can be used, having a larger specific surface and hence enabling thinner layers to be realized with the same light absorbance values. In this way, photovoltaic cells with higher efficiencies can be obtained due to the fact that the probability of recombination is reduced due to the path traversed by the electrons to the charge collecting electrode being shorter.
- Step (i) of the process, according to the present invention provides metal oxide semiconductor nano-particles prepared by a wet precipitation process.
- the expression "wet precipitation process” distinguishes the metal oxide semiconductor nano-particles used in the process, according to the present invention, from those prepared by non-wet chemical processes such as flame pyrolysis processes such as that operated by Degussa.
- Suitable titanium dioxide nano-particles produced by wet precipitation processes include:
- the layer contains at least one spectral sensitizer for the nano-porous metal oxide semiconductor selected from the group consisting of metal chalcogenide nano-particles with a band-gap between 1.5 and 2.9 eV, organic dyes, and metallo- organic dyes .
- the layer contains at least one spectral sensitizer for the nano-porous metal oxide semiconductor selected from the group consisting of metal oxides, metal sulphides and metal selenides.
- the layer contains at least one spectral sensitizer for the nano-porous metal oxide semiconductor which is a metal sulphide.
- the layer contains at least one spectral sensitizer for the nano-porous metal oxide semiconductor selected from the group consisting of lead sulphide, bismuth sulphide, cadmium sulphide, silver sulphide, antimony sulphide, indium sulphide, copper sulphide, cadmium selenide, copper selenide, indium selenide, cadmium telluride or a mixture of two or more thereof.
- EP-A 1 176 646, herein incorporated by reference, discloses a solid state p-n heterojunction comprising an electron conductor and a hole conductor, characterized in that if further comprises a sensitizing semiconductor, said sensitizing being located at an interface between said electron conductor and said hole conductor; and its application in a solid state sensitized photovolaic cell.
- the sensitizing semiconductor is in the form of particles adsorbed at the surface of said electron conductor and in a further preferred embodiment the sensitizing semiconductor is in the form of quantum dots, which according to a particularly preferred embodiment are particles consisting of PbS, CdS, Bi 2 S 3 , Sb 2 S 3 , Ag 2 S, InAs, CdTe, CdSe or HgTe or solid solutions of HgTe/CdTe or HgSe/CdSe.
- Suitable spectrally sensitizing organic dyes include cyanine, merocyanine and anionic dyes, such as:
- Suitable spectrally sensitizing metallo-organic dyes allowing for broad absorption of the solar spectrum include:
- Ruthenium 470 a ruthenium tris (2,2'bipyridyl-4, 4' dicarboxylato) dye from Solaronix ruthenium (II) dichloride
- Ruthenium 505 a ruthenium cis-bis (isocyanato) (2,2 'bipyridyl-4, 4' dye from Solaronix dicarboxylato) ruthenium (II)
- Ruthenium 535 a ruthenium cis-bis (isothiocyanato)bis (2,2' -bipyridyl- dye from Solaronix 4,4' -dicarboxylato) -ruthenium (II)
- Ruthenium 535 bis-TBA cis-bis (isothiocyanato)bis (2, 2 ' -bipyridyl- ruthenium dye from 4,4' -dicarboxylato) -ruthenium(II) bis- Solaronix tetrabutylammonium
- Ruthenium 620 Black Dye, (anion only) tris (isothiocyanato) - a ruthenium dye from ruthenium (II) -2 , 2 ' : 6 ' , 2 " -terpyridine-4 , 4 ' , 4 " • Solaronix tricarboxylic acid
- Supports for use according to the present invention include polymeric films, silicon, ceramics, oxides, glass, polymeric film reinforced glass, glass/plastic laminates, metal/plastic laminates, paper and laminated paper, optionally treated, provided with a subbing layer or other adhesion promoting means to aid adhesion to the layer configuration, according to the present invention.
- Suitable polymeric films are poly(ethylene terephthalate) , pol (ethylene naphthalate) , polystyrene, polyethersulphone, polycarbonate, polyacrylate, polyamide, polyimides, cellulosetriacetate, polyolefins and poly (vinyl chloride) , optionally treated by corona discharge or glow discharge or provided with a subbing layer.
- a photovoltaic device comprising a layer of a nano-porous metal oxide semiconductor obtainable by a process, according to the present invention.
- Photovoltaic devices comprising a layer of a nano-porous metal oxide semiconductor prepared by a process, according to the present invention, can be of two types: the regenerative type which converts light into electrical power leaving no net chemical change behind in which current-carrying electrons are transported to the anode and the external circuit and the holes are transported to the cathode where they are oxidized by the electrons from the external circuit and the photosynthetic type in which there are two redox systems one reacting with the holes at the surface of the semiconductor electrode and one reacting with the electrons entering the counter-electrode, for example, water is oxidized to oxygen at the semiconductor photoanode and reduced to hydrogen at the cathode.
- the hole transporting medium may be a liquid electrolyte supporting a redox reaction, a gel electrolyte supporting a redox reaction, an organic hole transporting material, which may be a low molecular weight material such as 2 , 2 ' , 7 , 7 ' -tetrakis (N,N-di-p-methoxyphenyl-amine) 9 , 9 ' - spirobifluorene (OMeTAD) or triphenylamine compounds or a polymer such as PPV-derivatives, poly (N-vinylcarbazole) etc., or inorganic semiconductors such as Cul, CuSCN etc.
- an organic hole transporting material which may be a low molecular weight material such as 2 , 2 ' , 7 , 7 ' -tetrakis (N,N-di-p-methoxyphenyl-amine) 9 , 9 ' - spirobifluorene (OMeTA
- the charge transporting process can be ionic, as for example in the case of a liquid electrolyte or gel electrolyte or electronic, as for example in the case of organic or inorganic hole transporting materials.
- regenerative photovoltaic devices can have a variety of internal structures in conformity with the end use. Conceivable forms are roughly divided into two types: structures which receive light from both sides and those which receive light from one side.
- An example of the former is a structure made up of a transparently conductive layer e.g. an ITO-layer or a PEDOT/PSS-containing layer and a transparent counter electrode electrically conductive layer e.g. an ITO-layer or a PEDOT/PSS-containing layer having interposed therebetween a photosensitive layer and a charge transporting lo layer.
- Such devices preferably have their sides sealed with a polymer, an adhesive etc. to prevent deterioration or volatilization of the inside substances.
- the external circuit connected to the electrically-conductive substrate and the counter electrode via the respective leads is well-known.
- the layer of a nano-porous metal oxide semiconductor prepared by a process, according to the present invention can be incorporated in hybrid photovoltaic compositions such as described in 1991 by Graetzel et al . in Nature, volume 353, pages 737-740, in 1998 by U. Bach et al . [see Nature, volume 395,
- Dispersion 2 P25 a nano-sized titanium dioxide with a mean particle size of 40 25 nm and a specific surface of 55 m 2 /g from DEGUSSA was mixed with ethanol to give a 25% by weight of solid material and then treated ultrasonically to produce Dispersion 1.
- Dispersion 2 P25 a nano-sized titanium dioxide with a mean particle size of 40 25 nm and a specific surface of 55 m 2 /g from DEGUSSA was mixed with ethanol to give a 25% by weight of solid material and then treated ultrasonically to produce Dispersion 1.
- Dispersion 2 P25 a nano-sized titanium dioxide with a mean particle size of 40 25 nm and a specific surface of 55 m 2 /g from DEGUSSA was mixed with ethanol to give a 25% by weight of solid material and then treated ultrasonically to produce Dispersion 1.
- Dispersion 2
- Ti-NanoxideTM T from SOLARONIX having a mean particle size of
- dispersion 3 a specific surface of 120 m2/g and containing 11% by weight of titanium oxide is called dispersion 3.
- Dispersions 2 or 3 were dried in a rotary evaporator, ground, spread on a sheet of glass and heated at 200, 350, 400 or 450°C, depending on the experiment, for 30 minutes in a rotary tube furnace. The resulting powders were then cooled, ground again and converted into a paste by adding water, ethanol and 10-20 UL of nitric acid. To prevent material loss, the paste was diluted with water and put in a bottle. The excess liquid was evaporated at a temperature of 100-150°C prior to use.
- Photovoltaic devices 1-46 were prepared by the following procedure:
- a glass plate (2 x 7 cm ) coated with conductive Sn0 2 :F (Pilkington TEC15/3) with a surface conductivity of ca 15 Ohm/square was ultrasonically cleaned in isopropanol for 5 minutes and then dried.
- the electrode was taped off at the borders and was doctor blade-coated in the middle (0.7 x 4.5 cm 2) with the titanium dioxide colloidal dispersion with or without dilution with ethanol depending upon the desired layer thickness.
- the layer thickness was determined mechanically with a diamond-tipped probe (Perthometer) and interferometry and are given in Tables 1 to 4.
- Coated glass electrodes with the nano titanium dioxide dispersions were heated at 450°C for 30 minutes, then cooled to
- Coated glass electrodes with the nano titanium dioxide dispersions were first dried at 110°C for 5 minutes, then, after cooling to room temperature (25°C) , a pressure of 500 bars was applied for 5 seconds. These pressure sintered coatings were then heated to 110-150°C, then immediately immersed in a 2 x 10 "4 M
- the back electrode (consisting of Sn0 2 :F glass (Pilkington TEC15/3) evaporated with platinum to catalyze reduction of the electrolyte)
- electrolyte was added through holes in the counter electrode.
- the electrolyte used was a solution of 0.5 M Lil, 0.05 M I 2 and 0.4 M t-butylpyridine in acetonitrile and was injected into the cell during cell assembly. The holes were then sealed with Surlyn® and a thin piece of glass. Conductive tape was attached on both long sides of the cell to collect the electricity during measurement. Measurements were performed immediately after cell assembly.
- the cell was irradiated with a Steuernagel Solar Constant 575 solar simulator with a metal halide 1 AM light source.
- the simulator was adjusted to about 1 sunequivalent.
- the electricity generated was recorded with a Type 2400 SMU Keithley electrometer.
- the most relevant parameter for these experiments was the short circuit current (I sc ) which is given for the examples in Tables 1 to 4.
- the open circuit voltage was in all cases almost the same (0.640 to 0.680), which was also the case for the fill factor (FF) (0.5 to 0.6). Cells with lower open circuit voltages than 0.640 V or fill factors lower than 0.5 were not considered.
- the short circuit currents, l ac for photovoltaic devices incorporating front electrodes with sintered titanium dioxide layers prepared with Dispersion 2 are given in Table 2 together with information concerning the heat pretreatment of Dispersion 2 and the sintering conditions used.
- the short circuit currents, I so device parameters for the photovoltaic devices of reference Devices 2, 8 and 9 are also included in Table 2 by way of reference.
- Dispersion 2 pretreated at 450°C was used, according to the present invention, instead of Dispersion 2 without pretreatment, then short circuit currents comparable with that observed with Device 14 incorporating a high temperature sintered layer of Dispersion 2 without pretreatment were observed, whether high pressure sintering was used, as in the case of Device 17, or high temperature sintering was used, as in the case of Device 16.
- Table 3 gives the results obtained with further photovoltaic devices with front electrodes prepared with Dispersion 2 for different titanium dioxide layer thicknesses, together with information regarding the heat pretreatment and sintering conditions.
- the short circuit currents, I sc , device parameters for the photovoltaic devices of comparative Device 14 and invention device 17 are also included in Table 3 for the sake of comparison.
- the short circuit currents, I sc for photovoltaic devices with front electrodes incorporating sintered titanium dioxide layers prepared with Dispersion 3 sintered at different pretreatment temperatures are given in Table 4 together with information concerning the heat treatment of the Dispersion and of the sintering conditions used.
- the short circuit currents, I sc device parameters for the photovoltaic devices of comparative Devices 14 and 15 are also included in Table 4 for the sake of comparison. Table 4 :
- Photovoltaic devices were prepared as described for Device numbers 46 to 49 except that the titanium dioxide layer thicknesses were different and that after sintering the titanium dioxide layers were heated for 5 minutes at 150°C before drying.
- the short circuit currents obtained with these devices, Devices 50 to 52, together with details over their titanium dioxide layer thickness and processing are given in Table 5 together with the results for Devices 46 to 49.
- the present invention may include any feature or combination of features disclosed herein either implicitly or explicitly or any generalisation thereof irrespective of whether it relates to the presently claimed invention.
Abstract
A process for preparing a layer of a nano-porous metal oxide semiconductor comprising the steps of: (i) providing metal oxide semiconductor nano-particles prepared by a wet precipitation process, (ii) heating said nano-particles at a temperature in the range of 250 to 600 °C, (iii) preparing a dispersion of said heat-treated nano-particles from step (ii), (iv) applying said dispersion prepared in step (iii) to a support to produce a coating; and (v) subjecting said coating to a pressure in the range of 100 to 1000 bar at a temperature below 250 °C; a layer of a nano-porous metal oxide semiconductor obtainable by this process; and a photovoltaic device comprising a layer of a nano-porous metal oxide semiconductor obtainable by this process.
Description
PROCESS FOR PREPARING NANO-POROUS METAL OXIDE SEMICONDUCTOR LAYERS
Field of the invention
The present invention relates to a process for preparing nano- porous metal oxide semiconductor layers .
Background of the invention.
There are two basic types of photoelectrochemical photovoltaic cells. The first type is the regenerative cell which converts light to electrical power leaving no net chemical change behind. Photons of energy exceeding that of the band gap generate electron- hole pairs, which are separated by the electrical field present in the space-charge layer. The negative charge carriers move through the bulk of the semiconductor to the current collector and the external circuit. The positive holes are driven to the surface where they are scavenged by the reduced form of the redox relay molecular (R) , oxidizing it: h* + R —» 0, the oxidized form. 0 is reduced back to R by the electrons that re-enter the cell from the external circuit. In the second type, photosynthetic cells, operate on a similar principle except that there are two redox systems: one reacting with the holes at the surface of the semiconductor electrode and the second reacting with the electrons entering the counter-electrode. In such cells water is typically oxidized to oxygen at the semiconductor photoanode and reduced to hydrogen at the cathode. Titanium dioxide has been the favoured semiconductor for these studies.
Mesoscopic or nano-porous semiconductor materials, minutely structured materials with an enormous internal surface area, have been developed for the first type of cell to improve the light capturing efficiency by increasing the area upon which the spectrally sensitizing species could adsorb. Arrays of nano- crystals of oxides such as Ti02, ZnO, Sn02 and Nb2Os or chalcogenides such as CdSe are the preferred semiconductor materials and are interconnected to allow electrical conduction to take place. A wet type solar cell having a porous film of dye-sensitized titanium dioxide semiconductor particles as a work electrode was expected to surpass an amorphous silicon solar cell in conversion efficiency and cost. These fundamental techniques were disclosed in 1991 by Graetzel et al. in Nature, volume 353, pages 737-740 and in US 4,927,721, US 5,350,644 and JP-A 05-504023. Graetzel et al
reported solid-state dye-sensitized mesoporous Ti02 solar cells with up to 33% photon to electron conversion efficiences.
In 1995 Tennakone et al. in Semiconductor Sci. Techno1., volume 10, page 1689 and O'Regan et al. in Chem. Mater., volume 7, page 1349 reported an all-solid-state solar cell consisting of a highly structured hetero-junction between a p- and n-type semiconductor with a absorber in between in which the p- semiconductor is CuSCN or Cul, the n-semiconductor is nano-porous titanium dioxide and the absorber is an organic dye. EP-A 1 176 646 discloses a solid state p-n heterojunction comprising an electron conductor and a hole conductor, characterized in that if further comprises a sensitizing semiconductor, said sensitizing being located at an interface between said electron conductor and said hole conductor; and its application in a solid state sensitized photovolaic cell.
A drawback in the manufacture of nano-porous metal oxide semiconductor layers for Graetzel photovoltaic cells is the high temperature needed for making the nano-porous metal oxide semiconductor layer. This is apparently needed to obtain sufficient contact between the nano-porous metal oxide particles to create a conductive pathway for the photogenerated charges (electrons) . Although the term sintering is not the appropriate one in this context, this term is often used to describe this heating process. Usually temperatures between 300 and 550°C are applied for 15 to 90 minutes . Such high temperatures are prohibitive for making photovoltaic cells on plastic and flexible substrates. Such cells would offer a myriad of advantages for this type of photovoltaic cell.
WO 00/72373 discloses a method for manufacturing a nanostructured porous film electrode, the method characterized by the steps of: preparing a binder-free suspension (21) of electrode material particles (11) in a volatile suspending agent (13), said particles substantially having a size within the nanometer scale, depositing the binder-free particle suspension (21) on a substrate (22) covered with a conducting film, removing the suspending agent (31) by evaporation, and compressing the particles to form an electrically conducting and mechanically stable nanostructured porous film. The process of WO 00/72373 enables the realization of the same solar cell performance with high pressure sintered nano- porous titanium dioxide layers as with conventional high temperature sintering. This finding was confirmed in 2000 by Pichot et al . in Langmuir, volume 16, pages 5625 to 5630, and in
2001 by Lindstrom et al. in Nano Letters, volume 1, pages 97 to 100. However, although this high pressure sintering process appears to work quite well with Degussa P25, a nano-sized titanium dioxide with a mean particle size of 30 nm and a specific surface of 50 m2/g from DEGUSSA, on a glass substrate or a plastic substrate, it has been found not to work with titanium dioxide particles made by a wet precipitation process.
There is a therefore a need for a low temperature process for preparing nano-porous metal oxide semiconductor layers with nano- particles prepared by wet precipitation processes on supports.
Aspects of the invention.
It is therefore an aspect of the present invention to provide a process for preparing nano-porous metal oxide semiconductor layers with nano-particles prepared by a wet precipitation process on both flexible and rigid supports.
It is a further aspect of the present invention to provide a photovoltaic cell incorporating a nano-porous metal oxide semiconductor layer prepared with nano-particles prepared by a wet precipitation process on flexible and rigid supports.
Further aspects and advantages of the invention will become apparent from the description hereinafter.
Summary of the invention.
It has been surprisingly found that layers of nano-porous metal oxide semiconductors can be prepared with nano-particles prepared by a wet precipitation process on supports by a process involving preheating the nano-particles at a temperature of 250 to 600°C, applying a coating of these preheated nano-particles to the support and subjecting the coating to a pressure of 100 to 1000 bar, without the application of the high temperatures needed for conventional sintering of titanium dioxide nano-particles i.e. 300 to 550°C.
Aspects of the present invention are realized by a process for preparing a layer of a nano-porous metal oxide semiconductor comprising the steps of: (i) providing metal oxide semiconductor nano-particles prepared by a wet precipitation process, (ii) heating said nano-particles at a temperature in the range of 250 to 600°C, (iii) preparing a dispersion of the heat-treated nano- particles from step (ii) , (iv) applying the dispersion of step
(iii) to a support to produce a coating; and (v) subjecting said coating to a pressure in the range of 100 to 1000 bar at a temperature below 250°C. An electrically conducting and mechanically stable nano-porous metal oxide semiconductor layer is thereby prepared.
Aspects of the present invention are also realized by a layer of a nano-porous metal oxide semiconductor obtainable by the above- mentioned process.
Aspects of the present invention are also realized by a photovoltaic device comprising a layer of a nano-porous metal oxide semiconductor obtainable by the above-mentioned process.
Preferred embodiments are disclosed in the dependent claims.
Detailed description of the invention.
Definitions
The term nano-porous metal oxide semiconductor means a metal oxide semiconductor having pores with a size of 100 nm or less and having an internal surface area of at least 5 m2/g and not more than 300 m7g.
The term chalcogenide means a binary compound containing a chalcogen and a more electropositive element or radical. A chalcogen is an element from group IV of the periodic table including oxygen, sulphur, selenium, tellurium and polonium.
The term "support" means a "self-supporting material" so as to distinguish it from a "layer" which may be coated on a support, but which is itself not self-supporting. It also includes any treatment necessary for, or layer applied to aid, adhesion to the support. The term continuous layer refers to a layer in a single plane covering the whole area of the support and not necessarily in direct contact with the support.
The term non-continuous layer refers to a layer in a single plane not covering the whole area of the support and not necessarily in direct contact with the support.
The term coating is used as a generic term including all means of applying a layer including all techniques for producing continuous layers, such as curtain coating, doctor-blade coating etc., and all techniques for producing non-continuous layers such as screen printing, ink jet printing, flexographic printing, and techniques for producing continuous layers.
The abbreviation PEDOT represents poly (3 , 4-ethylenedioxy- thiophene) .
The abbreviation PSS represents poly(styrene sulphonic acid) or poly (styrenesulphonate) .
Process for preparing a layer of a nano-porous metal oxide semiconductor
Aspects of the present invention are realized by a process for preparing a layer of a nano-porous metal oxide semiconductor comprising the steps of: (i) providing metal oxide semiconductor nano-particles prepared by a wet precipitation process, (ii) heating said nano-particles at a temperature in the range of 250 to 600°C, (iii) preparing a dispersion of the heat-treated nano- particles from step (ii) , (iv) applying the dispersion of step (iii) to a support to produce a coating; and (v) subjecting said coating to a pressure in the range of 100 to 1000 bar at a temperature below 250°C.
According to a first embodiment of the process, according to the present invention, the metal oxide semiconductor is n-type.
According to a second embodiment of the process, according to the present invention, the nano-porous metal oxide semiconductor has a band-gap of greater than 2.9 eV.
According to a third embodiment of the process, according to the present invention, the nano-porous metal oxide semiconductor nano-particle have a mean number averaged particle size < 20 run.
According to a fourth embodiment of the process, according to the present invention, the nano-porous metal oxide semiconductor is selected from the group consisting of titanium oxides, tin oxides, niobium oxides, tantalum oxides, tungsten oxides and zinc oxides. According to a fifth embodiment of the process, according to the present invention, the nano-porous metal oxide semiconductor is titanium dioxide.
According to a sixth embodiment of the process, according to the present invention, the nano-porous metal oxide semiconductor is titanium dioxide and between 80 and 100% thereof has an anatase morphology.
According to a seventh embodiment of the process, according to the present invention, the nano-porous metal oxide semiconductor is titanium dioxide and between 90 and 100% thereof has an anatase morphology.
According to an eighth embodiment of the process, according to the present invention, the pretreatment temperature is in the range of 300 to 500°C.
According to a ninth embodiment of the process, according to the present invention, the pretreatment temperature is in the range of 350 to 450°C.
According to a tenth embodiment of the process, according to the present invention, the sintering pressure is in the range of 300 to 700 bar. According to an eleventh embodiment of the process, according to the present invention, the sintering pressure is in the range of 400 to 600 bar.
According to a twelfth embodiment of the process, according to the present invention, the process further comprises heating the coating subjected to pressure from step (v) at a temperature of 100 to 200°C. According to a thirteenth embodiment of the process, according to the present invention, the process further comprises heating the coating subjected to pressure from step (v) at a temperature of 125 to 170°C.
According to a fourteenth embodiment of the process, according to the present invention, step (v) is carried out at a temperature above 0°C.
Step (ii) of the process, according to the present invention, is carried out under the atmosphere and pressure necessary to obtain metal oxide nano-particles with semiconducting properties. According to a fifteenth embodiment of the process, according to the present invention, step (ii) is carried out at under an ambient atmosphere i.e. at the pertaining ambient pressure and under the pertaining ambient atmosphere.
The sintering pressure for a particular layer of a nano-porous metal oxide semiconductor is dependent upon the nature of the support, a sintering pressure of 300 to 700 bar being suitable for glass supports and sintering pressures up to 1000 bar being suitable for polymeric film supports.
For efficient solar cells, the coating of the nano-porous Ti02 should be between 8 and 12 μm in order to have sufficient light absorption for generating power conversion efficiencies up to 5 to 8%. The thicker the titanium dioxide coating, the longer the pathway for the charges (electrons) have to be transported to the charge collecting electrode and the greater the probability of recombination occurring with resultant power conversion efficiency loss. In order to circumvent this problem smaller titanium dioxide nano-particles can be used, having a larger specific surface and
hence enabling thinner layers to be realized with the same light absorbance values. In this way, photovoltaic cells with higher efficiencies can be obtained due to the fact that the probability of recombination is reduced due to the path traversed by the electrons to the charge collecting electrode being shorter.
Step (i) of the process, according to the present invention, provides metal oxide semiconductor nano-particles prepared by a wet precipitation process. The expression "wet precipitation process" distinguishes the metal oxide semiconductor nano-particles used in the process, according to the present invention, from those prepared by non-wet chemical processes such as flame pyrolysis processes such as that operated by Degussa. Suitable titanium dioxide nano-particles produced by wet precipitation processes include:
which are often used as n-type semi-conductor nano-particles in making Graetzel-type photovoltaic cells, but can be also readily synthesized using fairly straightforward precipitation techniques familiar in colloid chemistry, such as described, for example, in 1997 by Barbe et al in Journal of the American Ceramic Society, volume 80(12), pages 3157 - 3171, herein incorporated by reference.
Spectral sensitization of nano-porous metal oxide semiconductor layers
Aspects of the present invention are also realized by a layer of a nano-porous metal oxide semiconductor obtainable by a process, according to the present invention. According to a first embodiment of the layer, according to the present invention, the layer contains at least one spectral sensitizer for the nano-porous metal oxide semiconductor selected from the group consisting of metal chalcogenide nano-particles with a band-gap between 1.5 and 2.9 eV, organic dyes, and metallo- organic dyes .
According to a second embodiment of the layer, according to the present invention, the layer contains at least one spectral sensitizer for the nano-porous metal oxide semiconductor selected from the group consisting of metal oxides, metal sulphides and metal selenides.
According to a third embodiment of the layer, according to the present invention, the layer contains at least one spectral sensitizer for the nano-porous metal oxide semiconductor which is a metal sulphide. According to a fourth embodiment of the layer, according to the present invention, the layer contains at least one spectral sensitizer for the nano-porous metal oxide semiconductor selected from the group consisting of lead sulphide, bismuth sulphide, cadmium sulphide, silver sulphide, antimony sulphide, indium sulphide, copper sulphide, cadmium selenide, copper selenide, indium selenide, cadmium telluride or a mixture of two or more thereof.
Vogel et al . in 1990 in Chemical Physics Letters, volume 174, page 241, herein incorporated by reference, reported the sensitization of highly porous Ti02 with in-situ prepared quantum size CdS particles (40-200A) , a photovoltage of 400 mV being achieved with visible light and high photon to current efficiences of greater than 70% being achieved at 400 nm and an energy conversion efficiency of 6.0% under monochromatic illumination with λ = 460 nm. In 1994 Hoyer et al. reported in Applied Physics, volume 66, page 349, that the inner surface of a porous titanium dioxide film could be homogeneously covered with isolated quantum dots and Vogel et al. reported in Journal of Physical Chemistry, volume 98, pages 3183-3188, herein incorporated by reference, the sensitization of various nanoporous wide-bandgap semiconductors, specifically Ti02, Nb205, Ta205, Sn02 and ZnO, with quantum-sized PbS, CdS, Ag2S, Sb2S3 and Bi2S3 and the use of quantum dot-sensitzed oxide semiconductors in liquid junction cells. The internal photocurrent quantum yield decreased with increasing particle diameter and decreased in the order Ti02 > ZnO > Nb205 > Sn02 > Ta205.
EP-A 1 176 646, herein incorporated by reference, discloses a solid state p-n heterojunction comprising an electron conductor and a hole conductor, characterized in that if further comprises a sensitizing semiconductor, said sensitizing being located at an interface between said electron conductor and said hole conductor; and its application in a solid state sensitized photovolaic cell.
In a preferred embodiment the sensitizing semiconductor is in the form of particles adsorbed at the surface of said electron conductor and in a further preferred embodiment the sensitizing semiconductor is in the form of quantum dots, which according to a particularly preferred embodiment are particles consisting of PbS, CdS, Bi2S3, Sb2S3, Ag2S, InAs, CdTe, CdSe or HgTe or solid solutions of HgTe/CdTe or HgSe/CdSe.
Suitable spectrally sensitizing organic dyes (SSOD) include cyanine, merocyanine and anionic dyes, such as:
Suitable spectrally sensitizing metallo-organic dyes allowing for broad absorption of the solar spectrum include:
chemical name
Ruthenium 470, a ruthenium tris (2,2'bipyridyl-4, 4' dicarboxylato) dye from Solaronix ruthenium (II) dichloride
Ruthenium 505, a ruthenium cis-bis (isocyanato) (2,2 'bipyridyl-4, 4' dye from Solaronix dicarboxylato) ruthenium (II)
Ruthenium 535, a ruthenium cis-bis (isothiocyanato)bis (2,2' -bipyridyl- dye from Solaronix 4,4' -dicarboxylato) -ruthenium (II)
Ruthenium 535 bis-TBA, cis-bis (isothiocyanato)bis (2, 2 ' -bipyridyl- ruthenium dye from 4,4' -dicarboxylato) -ruthenium(II) bis- Solaronix tetrabutylammonium
Ruthenium 620 "Black Dye", (anion only) tris (isothiocyanato) - a ruthenium dye from ruthenium (II) -2 , 2 ' : 6 ' , 2 " -terpyridine-4 , 4 ' , 4 " • Solaronix tricarboxylic acid
Support
Supports for use according to the present invention include polymeric films, silicon, ceramics, oxides, glass, polymeric film
reinforced glass, glass/plastic laminates, metal/plastic laminates, paper and laminated paper, optionally treated, provided with a subbing layer or other adhesion promoting means to aid adhesion to the layer configuration, according to the present invention. Suitable polymeric films are poly(ethylene terephthalate) , pol (ethylene naphthalate) , polystyrene, polyethersulphone, polycarbonate, polyacrylate, polyamide, polyimides, cellulosetriacetate, polyolefins and poly (vinyl chloride) , optionally treated by corona discharge or glow discharge or provided with a subbing layer.
Photovoltaic devices
Aspects of the present invention are realized by a photovoltaic device comprising a layer of a nano-porous metal oxide semiconductor obtainable by a process, according to the present invention.
Photovoltaic devices comprising a layer of a nano-porous metal oxide semiconductor prepared by a process, according to the present invention, can be of two types: the regenerative type which converts light into electrical power leaving no net chemical change behind in which current-carrying electrons are transported to the anode and the external circuit and the holes are transported to the cathode where they are oxidized by the electrons from the external circuit and the photosynthetic type in which there are two redox systems one reacting with the holes at the surface of the semiconductor electrode and one reacting with the electrons entering the counter-electrode, for example, water is oxidized to oxygen at the semiconductor photoanode and reduced to hydrogen at the cathode. In the case of the regenerative type of photovoltaic cell, as exemplified by the Graetzel cell, the hole transporting medium may be a liquid electrolyte supporting a redox reaction, a gel electrolyte supporting a redox reaction, an organic hole transporting material, which may be a low molecular weight material such as 2 , 2 ' , 7 , 7 ' -tetrakis (N,N-di-p-methoxyphenyl-amine) 9 , 9 ' - spirobifluorene (OMeTAD) or triphenylamine compounds or a polymer such as PPV-derivatives, poly (N-vinylcarbazole) etc., or inorganic semiconductors such as Cul, CuSCN etc. The charge transporting process can be ionic, as for example in the case of a liquid electrolyte or gel electrolyte or electronic, as for example in the case of organic or inorganic hole transporting materials.
Such regenerative photovoltaic devices can have a variety of internal structures in conformity with the end use. Conceivable forms are roughly divided into two types: structures which receive light from both sides and those which receive light from one side.
5 An example of the former is a structure made up of a transparently conductive layer e.g. an ITO-layer or a PEDOT/PSS-containing layer and a transparent counter electrode electrically conductive layer e.g. an ITO-layer or a PEDOT/PSS-containing layer having interposed therebetween a photosensitive layer and a charge transporting lo layer. Such devices preferably have their sides sealed with a polymer, an adhesive etc. to prevent deterioration or volatilization of the inside substances. The external circuit connected to the electrically-conductive substrate and the counter electrode via the respective leads is well-known. is Alternatively the layer of a nano-porous metal oxide semiconductor prepared by a process, according to the present invention, can be incorporated in hybrid photovoltaic compositions such as described in 1991 by Graetzel et al . in Nature, volume 353, pages 737-740, in 1998 by U. Bach et al . [see Nature, volume 395,
20 pages 583-585 (1998)] and in 2002 by W. U. Huynh et al. [see Science, volume 295, pages 2425-2427 (2002)].
Industrial application
25 Layers of nano-porous metal oxide semiconductors prepared according the process, according to the present invention, can be used in both regenerative and photosynthetic photovoltaic devices.
The invention is illustrated hereinafter by way of reference 30 and invention photovoltaic devices. The percentages and ratios given in these examples are by weight unless otherwise indicated.
EXAMPLE 1
35 Preparation of Titanium dioxide nano dispersions
Dispersion 1:
P25 a nano-sized titanium dioxide with a mean particle size of 40 25 nm and a specific surface of 55 m2/g from DEGUSSA was mixed with ethanol to give a 25% by weight of solid material and then treated ultrasonically to produce Dispersion 1.
Dispersion 2:
285 g of Ti-isopropoxide, 1800 mL of deionized water and 12.5 mL of nitric acid were stirred overnight at 80 °C without a cover. The total volume was made up to 1400 mL with deionized water and then autoclaved at 230°C for 14 hours. The concentration of the autoclaved colloid was reduced by evaporation to 16.2% by weight of solid material and then sufficient ethanol added to give a final solids content of 10.8% by weight, thereby producing Dispersion 2 (mean particle size of 13 nm, specific surface area 120 m2/g) .
Dispersion 3:
Ti-Nanoxide™ T from SOLARONIX, having a mean particle size of
13 nm, a specific surface of 120 m2/g and containing 11% by weight of titanium oxide is called dispersion 3.
Heat pretreatment of the Titanium dioxide nano dispersions
Dispersions 2 or 3 were dried in a rotary evaporator, ground, spread on a sheet of glass and heated at 200, 350, 400 or 450°C, depending on the experiment, for 30 minutes in a rotary tube furnace. The resulting powders were then cooled, ground again and converted into a paste by adding water, ethanol and 10-20 UL of nitric acid. To prevent material loss, the paste was diluted with water and put in a bottle. The excess liquid was evaporated at a temperature of 100-150°C prior to use.
Evaluation in photovoltaic devices with liquid electrolyte
Photovoltaic devices 1-46 were prepared by the following procedure:
Preparation of the front electrode:
2
A glass plate (2 x 7 cm ) coated with conductive Sn02:F (Pilkington TEC15/3) with a surface conductivity of ca 15 Ohm/square was ultrasonically cleaned in isopropanol for 5 minutes and then dried. The electrode was taped off at the borders and was doctor blade-coated in the middle (0.7 x 4.5 cm 2) with the titanium dioxide colloidal dispersion with or without dilution with ethanol depending upon the desired layer thickness.
The layer thickness was determined mechanically with a diamond-tipped probe (Perthometer) and interferometry and are given in Tables 1 to 4.
5 i) Front electrodes prepared by high temperature sintering of nano- porous titanium dioxide layers :
Coated glass electrodes with the nano titanium dioxide dispersions were heated at 450°C for 30 minutes, then cooled to
10 150°C by placing it on a hot plate at 150°C for 10 minutes, then immediately immersed in a 2 x 10~4 M solution of the Ruthenium 535 dye (SOLARONIX) for 15 to 17 hours followed by rinsing with acetonitrile to remove the non-adsorbed dye and drying at 50°C for several minutes . The front electrode thereby produced was is immediately used in assembling the corresponding photovoltaic cell.
ii) Front electrodes prepared by high pressure sintering of nano- porous titanium dioxide layers:
20 Coated glass electrodes with the nano titanium dioxide dispersions were first dried at 110°C for 5 minutes, then, after cooling to room temperature (25°C) , a pressure of 500 bars was applied for 5 seconds. These pressure sintered coatings were then heated to 110-150°C, then immediately immersed in a 2 x 10"4 M
25 solution of the Ruthenium 535 bis-TBA dye (SOLARONIX) for 15 to 17 hours followed by rinsing with acetonitrile to remove non-adsorbed dye and drying at 50°C for several minutes. The front electrode thereby produced was immediately used in assembling the corresponding photovoltaic cell.
30
Cell assembly
The back electrode (consisting of Sn02:F glass (Pilkington TEC15/3) evaporated with platinum to catalyze reduction of the electrolyte)
35 was sealed together with the front electrode with two pre-patterned layers of Surlyn®(DuPont) (2 x 7 cm where in the middle 1 x 6 cm had been removed) in between. This was performed at a temperature just above 100°C on a hotplate. As soon as the sealing was completed, the cell was cooled to room temperature (25°C) and
40 electrolyte was added through holes in the counter electrode. The electrolyte used was a solution of 0.5 M Lil, 0.05 M I2 and 0.4 M t-butylpyridine in acetonitrile and was injected into the cell
during cell assembly. The holes were then sealed with Surlyn® and a thin piece of glass. Conductive tape was attached on both long sides of the cell to collect the electricity during measurement. Measurements were performed immediately after cell assembly.
Device characterisation:
The cell was irradiated with a Steuernagel Solar Constant 575 solar simulator with a metal halide 1 AM light source. The simulator was adjusted to about 1 sunequivalent. The electricity generated was recorded with a Type 2400 SMU Keithley electrometer.
The most relevant parameter for these experiments was the short circuit current (Isc) which is given for the examples in Tables 1 to 4. The open circuit voltage was in all cases almost the same (0.640 to 0.680), which was also the case for the fill factor (FF) (0.5 to 0.6). Cells with lower open circuit voltages than 0.640 V or fill factors lower than 0.5 were not considered.
i) Photovoltai c devices incorporating sintered ti tani um dioxide layers prepared wi th Dispersion 1 :
The device parameters for reference photovoltaic devices incorporating front electrodes with sintered titanium dioxide prepared with Dispersion 1 together with the sintering conditions are given in Table 1.
Table 1:
ii) Photovoltai c devi ces incorporating sintered ti tanium dioxide layers prepared wi th Dispersions 1 and 2 :
The short circuit currents, lac, for photovoltaic devices incorporating front electrodes with sintered titanium dioxide layers prepared with Dispersion 2 are given in Table 2 together with information concerning the heat pretreatment of Dispersion 2 and the sintering conditions used. The short circuit currents, Iso, device parameters for the photovoltaic devices of reference Devices 2, 8 and 9 are also included in Table 2 by way of reference.
Table 2 :
The results in Table 2 show that photovoltaic cells incorporating high temperature sintered titanium dioxide layers, as expected from the prior art, exhibited high short circuit currents, that prepared with Dispersion 2 without heat pretreatment exhibiting a much higher short circuit currents than those exhibited by photovoltaic cells incorporating high temperature sintered titanium dioxide layers prepared with Dispersion 1. The results in Table 2 also show that for comparable titanium dioxide layer thicknesses the photovoltaic cell of Device 2 incorporating a high pressure sintered titanium dioxide layer prepared with Dispersion 1 exhibited a comparable short circuit current to that of Device 9 incorporating a high temperature
sintered titanium dioxide layer prepared with Dispersion 1, in accordance with the teaching of WO 00/72373.
However, if photovoltaic cells incorporated titanium layers prepared with Dispersion 2 without pretreatment, Device 15 incorporating a high pressure sintered layer exhibited a short circuit current which was much lower that that of Device 14 incorporating a high temperature sintered layer, at variance the teaching of WO 00/72373.
If, however, Dispersion 2 pretreated at 450°C was used, according to the present invention, instead of Dispersion 2 without pretreatment, then short circuit currents comparable with that observed with Device 14 incorporating a high temperature sintered layer of Dispersion 2 without pretreatment were observed, whether high pressure sintering was used, as in the case of Device 17, or high temperature sintering was used, as in the case of Device 16. This demonstrates the advantage of the present invention in making it possible to realize high short circuit currents in photovoltaic devices incorporating a high temperature sintering layer of a metal oxide semiconductor nano-particle dispersion prepared by a wet precipitation process, if the dispersion is subjected to prior thermal treatment.
iii) Influence of titanium dioxide layer thickness on photovoltaic device performance:
Table 3 gives the results obtained with further photovoltaic devices with front electrodes prepared with Dispersion 2 for different titanium dioxide layer thicknesses, together with information regarding the heat pretreatment and sintering conditions. The short circuit currents, Isc, device parameters for the photovoltaic devices of comparative Device 14 and invention device 17 are also included in Table 3 for the sake of comparison.
The results in Table 3 show that the short circuit current increased with titanium dioxide layer thickness for photovoltaic devices incorporating high pressure sintered titanium dioxide layer prepared with Dispersion 2 with heat pretreatment, according to the present invention, and moreover that the short circuit currents for photovoltaic devices with high temperature sintered titanium dioxide layers prepared with Dispersion 2 with heat pretreatment were comparable to those attained with photovoltaic devices incorporating high pressure sintered titanium dioxide layers at all titanium dioxide layer thicknesses.
Table 3
iv) Influence of the heat pretreatment temperature used for the titanium dioxide dispersion upon photovoltaic device performance:
The short circuit currents, Isc, for photovoltaic devices with front electrodes incorporating sintered titanium dioxide layers prepared with Dispersion 3 sintered at different pretreatment temperatures are given in Table 4 together with information concerning the heat treatment of the Dispersion and of the sintering conditions used. The short circuit currents, Isc, device parameters for the photovoltaic devices of comparative Devices 14 and 15 are also included in Table 4 for the sake of comparison.
Table 4 :
The results in Table 4 show that the short circuit current of photovoltaic devices incorporating a high pressure sintered titanium dioxide layer prepared with Dispersion 3 with heat pretreatment, according to the present invention, are comparable with the short circuit current of photovoltaic devices incorporating a high temperature sintered titanium dioxide layer prepared with Dispersion 3 with the same heat pretreatment for pretreatment temperatures of 350 and 400°C, see the results for Devices 42 and 44 versus Devices 41 and 43.
The short circuit currents of a photovoltaic devices incorporating a high pressure sintered titanium dioxide layer prepared with Dispersion 3 heat pretreated at 450°C, Devices 46-49, were slightly below that of Device 45 incorporating a titanium dioxide layer prepared with Dispersion 3 with the heat pretreatment at 450°C and sintered at 450°C.
Furthermore, the short circuit current of a photovoltaic device incorporating a high pressure sintered titanium dioxide layer prepared with Dispersion 3 with heat pretreatment at 200°C, Device 40, was significantly below the short circuit current of that of Device 39 incorporating a high temperature sintered titanium dioxide layer prepared with Dispersion 3 with heat pretreatment at 200°C.
EXAMPLE 2
Low temperature heat treatment after high pressure sintering
Photovoltaic devices were prepared as described for Device numbers 46 to 49 except that the titanium dioxide layer thicknesses were different and that after sintering the titanium dioxide layers were heated for 5 minutes at 150°C before drying. The short circuit currents obtained with these devices, Devices 50 to 52, together with details over their titanium dioxide layer thickness and processing are given in Table 5 together with the results for Devices 46 to 49.
Table 5:
Taking into account the increase in short-circuit current with increasing titanium dioxide layer thickness, it is clear that post- pressure sintering heating at moderate temperatures increased the short-circuit current observed.
The present invention may include any feature or combination of features disclosed herein either implicitly or explicitly or any generalisation thereof irrespective of whether it relates to the presently claimed invention. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.
Claims
1. A process for preparing a layer of a nano-porous metal oxide semiconductor comprising the steps of: (i) providing metal oxide semiconductor nano-particles prepared by a wet precipitation process, (ii) heating said nano-particles at a temperature in the range of 250 to 600°C, (iii) preparing a dispersion of said heat-treated nano-particles from step (ii) , (iv) applying said dispersion prepared in step (iii) to a support to produce a coating; and (v) subjecting said coating to a pressure in the range of 100 to 1000 bar at a temperature below 250°C.
2. Process according to claim 1, wherein said metal oxide is selected from the group consisting of titanium oxides, tin oxides, niobium oxides, tantalum oxides, tungsten oxides and zinc oxides.
3. Process according to claim 1, wherein said pretreatment temperature is in the range of 300 to 500°C.
4. Process according to claim 1, wherein said sintering pressure is in the range 400 to 600 bar.
5. Process according to claim 1, wherein the process further comprises heating said coating subjected to pressure from step (v) at a temperature of 100 to 200°C.
6. Process according to claim 1, wherein said nano-porous metal oxide semiconductor has a band-gap of greater than 2.9 eV.
7. Process according to claim 1, wherein said nano-porous metal oxide nano-particles have a mean number averaged particle size < 20 nm.
8. A layer of a nano-porous metal oxide semiconductor obtainable by a process for preparing a layer of a nano-porous metal oxide semiconductor comprising the steps of: (i) providing metal oxide semiconductor nano-particles prepared by a wet precipitation process, (ii) heating said nano-particles at a temperature in the range of 250 to 600°C, (iii) preparing a dispersion of said heat-treated nano-particles from step (ii) , (iv) applying said dispersion prepared in step (iii) to a support to produce a coating; and (v) subjecting said coating to a pressure in the range of 100 to 1000 bar at a temperature between 20 and 250°C.
9. Layer according to claim 8, wherein said layer contains at least one spectral sensitizer for the nano-porous metal oxide semiconductor selected from the group consisting of metal chalcogenide nano-particles with a band-gap between 1.5 and 2.9 ev, organic dyes, and metallo-organic dyes.
10. A photovoltaic device comprising a layer of a nano-porous metal oxide semiconductor obtainable by a process for preparing a layer of a nano-porous metal oxide semiconductor comprising the steps of: (i) providing metal oxide semiconductor nano-particles prepared by a wet precipitation process, (ii) heating said nano-particles at a temperature in the range of 250 to 600°C, (iii) preparing a dispersion of said heat-treated nano-particles from step (ii) , (iv) applying said dispersion prepared in step (iii) to a support to produce a coating; and (v) subjecting said coating to a pressure in the range of 100 to 1000 bar at a temperature below 250°C.
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| AU2002336101A AU2002336101A1 (en) | 2002-09-12 | 2002-09-12 | Process for preparing nano-porous metal oxide semiconductor layers |
| JP2004535037A JP2005539377A (en) | 2002-09-12 | 2002-09-12 | Preparation of nano-porous metal oxide semiconductor layer |
| EP02769994A EP1540679A1 (en) | 2002-09-12 | 2002-09-12 | Process for preparing nano-porous metal oxide semiconductor layers |
| PCT/EP2002/010270 WO2004025675A1 (en) | 2002-09-12 | 2002-09-12 | Process for preparing nano-porous metal oxide semiconductor layers |
| US10/659,982 US6929970B2 (en) | 2002-09-12 | 2003-09-11 | Process for preparing nano-porous metal oxide semiconductor layers |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5616366A (en) * | 1994-04-20 | 1997-04-01 | Valence Technology, Inc. | Method for producing low porosity electrode |
| WO2000072373A1 (en) * | 1999-05-25 | 2000-11-30 | Forskarpatent I Uppsala Ab | Method for manufacturing nanostructured thin film electrodes |
| US6240846B1 (en) * | 1998-08-29 | 2001-06-05 | Agfa-Gevaert | Recording material comprising a substrate and a ceramic layer applied to a surface of the substrate |
| EP1164603A2 (en) * | 2000-06-15 | 2001-12-19 | Fuji Photo Film Co., Ltd. | Dye sensitized solar cell |
-
2002
- 2002-09-12 EP EP02769994A patent/EP1540679A1/en not_active Withdrawn
- 2002-09-12 AU AU2002336101A patent/AU2002336101A1/en not_active Abandoned
- 2002-09-12 WO PCT/EP2002/010270 patent/WO2004025675A1/en active Application Filing
- 2002-09-12 JP JP2004535037A patent/JP2005539377A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5616366A (en) * | 1994-04-20 | 1997-04-01 | Valence Technology, Inc. | Method for producing low porosity electrode |
| US6240846B1 (en) * | 1998-08-29 | 2001-06-05 | Agfa-Gevaert | Recording material comprising a substrate and a ceramic layer applied to a surface of the substrate |
| WO2000072373A1 (en) * | 1999-05-25 | 2000-11-30 | Forskarpatent I Uppsala Ab | Method for manufacturing nanostructured thin film electrodes |
| EP1164603A2 (en) * | 2000-06-15 | 2001-12-19 | Fuji Photo Film Co., Ltd. | Dye sensitized solar cell |
Non-Patent Citations (3)
| Title |
|---|
| BARBE C J ET AL: "MESOPOROUS TIO2 ELECTRODES FOR PHOTOVOLTAIC APPLICATIONS", MATERIALS RESEARCH SOCIETY SYMPOSIUM PROCEEDINGS, MATERIALS RESEARCH SOCIETY, PITTSBURG, PA, US, vol. 431, 11 April 1996 (1996-04-11), pages 129 - 134, XP001025709, ISSN: 0272-9172 * |
| HEPEL M ET AL: "DYE PHOTOSENSITIZATION OF TRANSITION METAL OXIDE FILM PHOTOELECTRODES", PROCEEDINGS OF THE SYMPOSIUM ON PHOTOELECTROCHEMISTRY. PARIS, AUG. 31 - SEPT. 5, 1997, PENNINGTON, NJ, ELECTROCHEMICAL SOC, US, vol. PV 97-20, 21 July 1999 (1999-07-21), pages 141 - 151, XP000792150, ISBN: 1-56677-148-X * |
| P.M. SOMMERLING ET AL.: "Flexible dye-sensitized nanocrystalline TiO2 solar cells", 16TH EUROPEAN PHOTOVOLTAIC SOLAR ENERGY CONFERENCE, 1 May 2000 (2000-05-01) - 5 May 2000 (2000-05-05), Glasgow, UK, pages 67 - 71, XP001138243 * |
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| EP1540679A1 (en) | 2005-06-15 |
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