GB2554119A - Stable electrolyte formulations - Google Patents

Abstract

Use of benzimidazole or benzimidazole derivatives optionally together with benzimidazolium salts in electrolyte formulations comprising iodine in at least 3.5 weight% and cyanoborate anions optionally with amounts up to 0.5 weight% of further additives, such as alkali metal iodides and/or thiocyanates, weight percentages are based on the total weight of the electrolyte formulations. The maximum weight of iodine may be 10%, the cyanoborate anions may be 4 to 25%, and the benzimidazole may be 1 to 20%. Solvents at 25-70% and iodides at 10-50% may also be included. Guanidinium thiocyanate, 1-ethyl-3-methylimidazolium thiocyanate, 1,3-dimethylimidazolium iodide, 1-ethyl-3-methylimiazolium or 1-ethyl-3-methylimidazolium iodide may be included. The cyanoborate anions may consist of monohydridotricyanoborate and dihydridodicyanoborate groups. Organic cations such as sulfonium groups may be included. The electrolyte may be used in a solar cell.

Description

Stable electrolyte formulations Field of the invention

The present Invention relates to the use of benzimidazole or benzimidazole derivatives optionally together with benzimidazollum salts in electrolyte formulations comprising iodine in at least 3,5 wt% and oyanoborate anions in absence or in conjunction with amounts up to 0.5 wt% of further additives such as alkali metal iodides and/or thiocyanates where ail weight percentages are based on the total weight of the electrolyte formulations, specific electrolyte formulations and a device comprising them,

Background of the Invention

Electrolyte formulations using ionic compounds having oyanoborate anions for use in optoelectronic devices, preferably for solar cells, are well known and have demonstrated both thermal and light soaking stability as described in Daibin Kuang Peng et a!, J. Chem, Soo. 2008, 128, 7732, Yu Bai et at, Nat Mat 2008, 7, 626 and WO 2007/093981 In WO 2012/183489, a new low cost oyanoborate, namely hydrkjoiricyanoboate, have been shown to give high performance in optoelectronic devices. In WO 2012/163490, dihydridodicyanoborates are described to give high performance in optoelectronic devices. In WO 2011/085984, difiuorodicyanoborates are described to give high performance in optoelectronic devices, especially in dye-sensitized solar cells, in WO 2012/041437, monofluorotricyanoborates are described to give high performance in optoelectronic devices, especially in dye-sensitized solar cells. In WO 2013/010841, alkyifricyanoboraies are described to give high performance in optoelectronic devices, especially in dye-sensitized solar cells, ft is also known from M. Marszalek et al, Adv. Energy Mater, 2014, 4,1301235 that electrolyte formulations comprising tefracyanoborates with sulfolane increase the overall performance. it &amp; also known from 2e Yu et a!, J. Piiys. Chenv C 2010,114, ^2$30< that additives suchas nmiethybhenziroidazofa or n~butyi~ ^rjmldazole together with guan id imum thiocyanate in: electrolyte ^^yiatlons: comprising fetracyanohorates.^ iodine to generate the ly/l* redoy couple, enhance device oerforrrianC6 ano' '0n^ temi stability. The: Same:1 combined effect of _ ^thy!feehzioddazole arid pea hidihiym thiocyanate Is also ^escrjfced in G. P. S. Lao, ChemSusiibem 2015, 8 (2), 255. ,. j- known that n-methyhbenzimidazofe or hfeutyl-henzimidazde it ^ ms? fed substituted by 1 -benzimidazole according to Hitachi Kusama t aj γ PhoicK Chem. 2004,182,,441,. Jungsik Min οί;|Ι,Μ Photo. Cherrl Mil.249, 148, WO 2012/163489 or US 8802976, yg 9s 183,992 describes a dye-sensitized solar cell having high durabi IHy a nd therm at resistance, and preventing elution ofa platinum qroup catalyst from a catalytic electrode comprising an electrolyte solution containing at feast one sulfur material In a dissolved state and when the eyitbr niatariaS is guanldlnium thiocyanate, a oqneentration df the guanidinfum thicdyahate is less than 0,1 hi in the etectrolyte solution. There is no disclosure to; use compounds having eyancKvaia ah1ons1h::|hes$'e!|#0iyle solutions, fn ai1lthe:pnor art eiectroiyte formulations, the combination ofa benzimidazole or benzimidazole derivative with at least one ferther: additive such as guanldlniurh fhiocyahate is reported to be essential to enable high peifermanoe or stebilrfy.

However, there continues to foe a demand for electrolyte formulations comprising ionic compounds having cyanofeorate anions, preferably mpnohydriddfrfcyanohorefes a π d/o r ci ihyd ridodlcy anobo rates, wh ieh can be used in optoelectronic devices resulting in good to high

Sworn! stability and light sfebtlify and high power conversion efficiency of said device.

Thermal and light stability of optoeiectropid devices mostly depend on more than one part of the device. Values depend heayely e.g, on the quality of the electrode, the electrolyte layer and the sooting. Ideally, the optoelectronic device is thermally stable more than 500 hours, preferably more than 1000 hours, particularly preferably more than 2000 hours white thermally stable means mat the device is treated at 80-© at this time.. Ideally, the optoelectronic device is stable on light soaking more than 500 hours, preferably more than 1000 hours, particularly preferably more than 2000 hours while stable on light soaking means that the device Is treated pnder simulated AiWI ,6 G light and a light intensity ofca. 1000 \/Wm® at this time.

The object of the invention is therefore to provide stableeiectmlyte .'fdfmutdtionsifd bemused in optoelectronic devices such as solar cells, preferably dye-sehsltlaed' solar cells, where at least one parameter selected from1 the group thermal stability, light stability and power oehveralpn.eiipiency Is increased compared to prior art electrolyte formul^ftens whti@:.m.atntainingihergQbdt:to high performance of the "Other two parameters.

The obieobis solved by the subject of the present claims. eumnalngly It was feond that oyanoborate based electrolyte formulations, particularly hydridocyanoborate based electrolyte formulations, including 1-benzimidazole or benzimidazole derivatives as additives but in absence or in conjunction with very low amount of further'additives result in high performance arid high stability optbelectronlo devices, particularly dye-sensitized solar ceils. β]:10]ίΏβ£ϊ..οί..Ι^ίην6!3ΐίΜ

The invention relates to the use of foefizlfriliazote or feenaml&amp;zofe derivatives optionally together with benzlmidazolium satis in electrolyte formulations comprising Iodine in at least 3,5 wt% and cyanoborafe arrhns In absence or in conjunction with amounts tig to 0,5 wt% of further additives where ail weight percentages are based ary the total weight of the electrolyte formulation.

The Invention further relates to an electrolyte formulation consisting of (I) 4 to 25 wt% of an lohto compourid having cyanoborate anions; (si) 3.5 to TO wt% iodine; {III} 10 to SO wt% of one or more iodides having an organic cation;

Civ) 1 to· 20 wt% of benzimidazole or a benzimidazole, derivative of formula (I)

(!) wherein R° and R1 are independently of each other a stralghbchain or branched alkyl group having 1 to 12 C atoms which may comprise an 0 atom or an S atom, n is 0,1,2, 3 or 4 and R2 is H or a straight-ohain or branched alkyl group having 1 to 12 C atoms which may comprise an: O atom or an S atom; {v) 0 to 5 wt% of a benzi mldazoilum salt; (vi) 0 to 0,5 wfRo of further additives and (vii) 25 to 70 wt% of one or more solvents, wherein the amounts in wt% ore based on fNe fotal·weight of thee lectroiyte formulation.

The invention farther relates to a device comprising the electrolyte formuiation as described before.

Detailed: Description of the Invention The inyehfton further relates to the use of benzimidazole Of benaWdaBole derivatives pptionaiiy together with benzimidazoilum saitsIneiecW pemppsthgiibdiha in at least TSiwiffs and cyahoborate anions in absence or in conjunction with amounts up to 0.5 wt% of further additives such as alkali metal iodides and/or thiocyanates where afweight percehtaiOs are based on the total weight of the electrolyte forrouiations wherein the further additives are alfeali metal iodides and/or thiocyanate salts, ^Ikah metal; iodides are preferably lithium iodide: sodium iodide, potassfuin Iodide:or cesium iodide. According to the invention, the amount of lithium iodide alone or in combination with thiocyanate salts Is reduced.

The cation of the thiocyanate salt to be used as additive in electrolyte formulations is not restricted per se. If may be inorganic or organic. Frefefabiyt the thiocyanate salts have organic cations selected from the graup comprising sultenium, oxonlumt ammapiom, phosphonium, uronium, fhioufdnipm, §panidinidm cations or heferobycilc eations, Padiculsdy preferably, the thiocyanate sails have organic cations selected from guanidinium cations and heterocyclic cations. ^pccrdlng to the inyention:, the amount ofthi:;#itecyansfe^ltS'ihaylf^. gyanldrbium cations or heterocyclic cations atone or in combinatibn with alkali metal iodides is reduced. Preferred thiocyanate salts ate gadnldihium thiocyanate and 1-ethyi'-3aTiethyi;midazoiium thiocyanate.

The invention therefore relates to the useas described before whereinthe further additives ate Jithium iodide and/or §yanidiniurrt :fhtocya.h:a!e artd/or 1 mth^d^-methyiimidazoiium thiocyanate. i|n one embodiment of the inyentioniitffsp use the benzimidazoie or benzimidazole dadyative asdeadhbed befote in :eg ibid.6 wt% of alkali metsi sails as "described btgfeipahty described before and in the absence of thiocyanate salts.

In another ©mbodifaedlof theunvention i is preferred to use the benzimidazole or benzimidazole derivative as described heforeintbe salts and thiocyanate sails as described before or preferably described before,

Th# fohie dompbunds having cysnoborate anions arepreferably ionic compounds haying anions selected from the group consisting of terra cyanobomte * mboofiubmtrte dlttu^ monohydridotrioyahohorafe, dihydridooicyanoborate and aI Kyltrlcya noborate In which the alkyl group Is sfraighbchain or brahphed haying 1 to 4 C atoms. The Ionic compounds ore paiScylatly preferably ionic Pompounds haying monohydodotHcyanoborate or dlhydndodtcyanoborate anions. The most preferred ionic compound according to the invention is an Ionic compound with a rnonohydridotricyanphorete anion.

The invention therefore relates to the use as described or preferably described before wherein the ionic compounds are ionic compounds having anions selected from the group consisting of ietraoyanoboraie,. mohofiucrothoyanabotate, dif!uorodicyanoborats, •alkyltricyanoboraie ;n which the alkyl group is straight-chain or br anohed paving· 1 to 4 C atoms, A,sp:ih-hchaisi or br|hohbd::ilk:yl gmyp'Mvingf % td,4. C atoms denotes an alkyl group haying 1 2, $;w4,':C atoms, for example methyivSthyl, iso-propyl, n-propyl /so-butyi, n-butyl and fed-butyl.

The Ionic compounds haying cyanoborate anions as described before or preferably described before, are preferably ionic liquids.

Ionic liquids or liquid salts are ionic species which consist of an organic cation and an anion. They do not contain any neutral molecules and usually have melting points below3?8 K.

The organic cation W*' of the .ionic ccrn^dhd haying a cyanoborate anion· is not restricted,

Preferably, the organic cation of the Ionic compound having a cyanobarato anion as described before or preferably described before to be used ofbeing part of the electrolyte ^ accordlngio the invention is an organic cation selected from the group comprising; auifoniunt, pKohlurnJ::ammpniutb uroniurn, thtouronium, guanidinium cations or heterocyclic cations.

Particularly prefsrablyy the organic cation of the sonic compound is based on Imidazole or pyrroiidsh such as i d -diaiylpyrrolidiniym, 1-aikyl-l-alkoxyalkylpynOlldiniu m, 1 ^dlalkyilmldazo iium, 1 -aikax^tkypa-alkylimldazoitum and l^alkenyl-S-alkylimidazolium.

Preferred ll-dialkylpyrrDiidinium cations are, for example, 11-dimethy^yrrol^ifiitim, 1 -met h yl 1 -etfty Ipy rroiidirt s u m > 1 -methyM ~ propylpyrroildiniura, 1-methyll -butyipyrrolidinium, 1 -melhyj-1 -pentyl pyrrolidiniurn.. 1 orsathyi-l-hexyipyrroSsdinium, 1 -methyll-hepfyl pyrroiidiniurri, 1 -methyi-l-qotyfpyrrofsdiniunl, 1 -methyi-1 -nonyt-pyrrpiidiniura, 1 -mefhyll -deqrlpyrrolsdiRiyhi, 1,1 -disthylpyrroidinsum, 1 -ethyl 1 -p ro py Ipyrrotidin to m, 1 -ethyl 1 -duly ipy rroli dins um, 1 -ethyl-1 -pentylpyrreiidipidm, l-etNyl-l-fiexylpyrrolidinlum, 1~ethyl1~beptyl pyrrelidfeium, 1-ethyM -aciyipyrro!idiniu?% 1 -ethyll-nonyipyrroikiln-fem, 1-ethyll-deoylpyrrplMsnlym, Id-dlprppylpyrrdlidmium, 1-propyi-1 -methylpyrrslidlnlym, 1 -propyll -buiylpyrroltdlnsuw, 1-propyl-1-peniylpyrro1tdi.yiyni( l-propyll-hexylpyrrsiidinfym, 1 -propyll -heptyi-py rrottclfn ium, 1 -propyl f~odiyipyrrofidin|ym,. 1 -propyl 1 -nonyi-pyrrolldlnium, 1 -propyll -deeyipyrrelsdlyium, 1 f 1 -dlbutylpyrrolldlnium, 1~pytyl-1-ni0thylpyrroffdinrums 1?butyM -pentyipyrr©lidfeiPtf)f 1-buty|-1~ bexylpyrrdSidfelum, 1 ~bu Ly 11 -hep iy ipyrrol kli n ;u m, 1 -byiyll -octyl pyrrolldinium, 1-btityll-oonylpyrrolidinferii: l-butyll-decyl pyrroiidiniunp 1 ,.1 -dipeniylpyrrolidinium, 1-pentyl-1 -hexyipyrrolidiniufe* 1~pentyl1 -bepiylpyrrolidffeum, l-ppntyll-oefyfpyrsxdldtoiurn, 1-pentyl l-nonyipyrroltdlniunii l-pentylt-decylpyrroiidinium, 1,1-dihexyl pyrrolidlniuhi, 1 -hexyll -heptyipyrrotidiniurri, 1 -bexyll-optyl-pyrroSidimum, 1 -hexyll-nonyipyrroSidiruum, 1-hexyl 1-decyipyrrofidin~ turn, ll-dihexylpyrrolidmiupi, 1-bexyi-l-heptylpyrroiidiniym, 1-hexyl 1 -oetylpyrrslrdiniurn, l-hexyll-nopylpyrrolldinfem, 1 -hexyll-decyl· py rrdi icltnt urn s 1, ΐ-d iheptyipyrroisdinium, 1 -hepty 1 1 -oeiytpyrroiid spium, 1-hepty 11 -nony ipyrroild s nium, 1 -heptyll -deeylpyr roirdmlum > 11 ~ dloctyipyrrolidiniurn, 1 -optyll-nonylpyrrolldinium, 1 -octyl-1 -decyt-pyrrolid-nsurn, 1,1 -dinonyipyrroltdinium, 1 -nonyS-l -deqySpyrroiidlnrum or 1 y 1 -didecylpyrroldlnium Very particular preference Is given to 1 -biityi-l-feethylpyrrolidihlum or t-propyll -methytpyrirolidihlbm.

Pr^sferrecl 1 ϊuits cations are, for example, i^methoxymeihy!-1-nieftyf-i3y^r&amp;Hdfn1yrn, 1 -mefhoxymelhyl-l -ethyl-pytroildinium, 1'-(2-rr]ethoxyethy!)-1-methylpyrroiidmium> 1-(2-mefhoxyethyiM -ethylpyrroiidiniyrn, 1 -{2^Bisfexyethy1^1-propy4 pyrfoifdf niUni > 1'(2«methoxyethyl)·· i-butylpyrroiidinium, 1-(2-ethyi >-1 -rriethylpyrrofid I n ium, l-athoxymetllybf-mptNyb pyrroiidinium·. 1 li~ 1 πiurp. \/6iry parlicular preference is given ίο 1-(2-methoxyeihyi}-1'niet1iySpyrro;idini'um,

Preferred' 1,3-dialkySimidazofiym cations are, for example, 1 -etliyi-3-metPylimidaxofipm, 1e-rpethyt-3'pro|3yflrrif#a^0tiMFB, 1 f^i3^ triinefhylimsdazcSsyni:, 1 -propyl-2,3- dpothyiimidazoiiupi, 1 ^btEty 1-2,3-dirtiefitiylht110s^#liu^^ l-butyl-3-methylmlddzoiium, 1 'methyi-S-pentylimidaxoisum, i-efeyt^prapyP fmtdazoliujti, t^M^y f-etbyi-S-pentylimidazolium, 1~|yiyf-3ferppyfe 1 f3-dimethylimidazoliuni: tS-diethyk imidazoiium, 1,3~dipropy!imidazo!ium, 1 ^-dibutyiimidazoiiurn, 1<3-dfpeotyii midazoliafn, 1,3-dfhexy iirpidazeiiy m, 1,3-diheptyiimidazoiium, 1,3-droctylimidazaiium, 1 .S-dinonyfirnidazolium, 1,3-dfdecyiimidazoiium, 1 -hexyi-3-methyHmidazoiium; 1-heptyi~3-metnyl~ rmidazeiibtfe 1 1 -methyi-3-nonyl-· imldazoliam* 1-dacyl-3-rriethyllrrifdazol iumi i -sthykS-bexyl·: irnidizollam,:!-ethyi-3-Hepfyiimlddzoliumi, 1~etnyi-3~ocfyismidazoiium. 1 -ethyl^S-nonyiimtdazpifym or 1 -decyi-S-ethytimidazoirum. Particularly preferred cations pro 1 ~eihyl~3~meilr/limidazoiiyrn: 1 -bufyl-3~methyl· jraidazollum or l-mefey!-3feropy^^

Preferred· 1felkoxyaIkyI-3fe!i^ are, for example 1- feetdoxymetdyl~3-mefdylimidaz 1-mefeoxyrnefeyi-S-ethylimidazoliurn, 1 -niethoxymethyi~3-butytimidazoiium, 1 -(2- π, 3 “(2-rnet h oxy e t hy I) - 3-eth y I - frnidozdlyni, l-panethoxyethySi-S-propylirnidazolium, 1-(2- m^Qxyethyl^S^buiylirBidazoftum, 1 ~f2~0Hioxyeihy1)"3~methyl~ imidazolkiniyl'ethoxymetliy^S^iiethylinikdazoHum,

Preferred l-aikenyi-S-alkylimidazoliuni cations are, for example 1-alykS-fflethyl-Imidaaolium or 1 -aSiyl-2,3:~dime|hyli:mtdaxsiturii.

The ionic compounds Having cyaftpboraie anions described before or preferably described before, have particularly preferably Imidazolium cations as: described before,

Particularly suitable organic cations of the ionic compounds Having eyanobor ate anions as described before of preferably .described before, are 4%utyi4~m®tb^pyritdtld|niumf 1 fotbyhSmsetbyt-imidazotiurn, 1 -ethyHS^foimethylimidamlium, l-p-methoxyeihyfoS-methySimidazokuny 1 -putyj-3»m^fhyBitiid^oiiufrii, feallyhd-methyiimidazDlium,: ir«iiyP2,3>dios^ylimidazoiiym or 1,1» dimefiiylpyrroildiiliym,

The most preferred cation of the ionic compounds having dyanoborafe anions as described before or preferabiy described before Is 1 -ethykS-methy llmidazoliurn.

The electrolyte formulation oomprlslrtg: benzimidazole dr benzimidazole derivatives according to the invention preferably comprises the ionic compound as described or preferably described before in 4 to 21 wt% based on the total weight of the electrolyte formulation.

The electrolyte· formulation comprising, benzimidazole or benzimidazole derivatives according to the invention particularly preferably comprises the ionic compound as described or preferably described before in 5 to 20 wi% based on the total weight of the electrolyte formulation.

Bebzirhlbazoie: is a non~substiiuted heierocyelus which may also be named 1-benzimidazole..

BenziOltdSaola derivatives are pre%ra^|y ^substituted benzimidazoles which may optionally ba substituted on the heterocydus.

Bfefafree! benzimidazole derivStives are compounets of form ula (1} Φ wherein and H1 are iodependentiyM each dthir a straight-chain or branched alkyl group having i to e atoms which may comprise ari O atom or an S atom, n isO, 1, 2, 3 or 4 and R% H or a straight-chain or branched alkyl group having 1 to 12 C atomswhich may compare an 0 atom or an S atom

The invention therefore delates to the use as described or preferably described before wherein the benzimidazole derivative is a compound of formula |i}

(1} wherein R*3 and R1 are independently of each other a Mraight-ebain or branched alKy! group Having i to 12 C atoms which maycompme an 0 atom or an S atom, ή is 0,1,2, 3 or 4 and R2 is H or a straight-chain or branched alkyl group paving 1 to 12 C atoms which rnay comprise an O atom or an S atom. A straight-chain or branched aikyi group baying 1 to 12 C atoms denotes an aikyi group having 1,2« 3« 4, δ, 8, 7, 8, 9, 10,11 or 12 C atoms, for example methyl, ethyl, Iso-propyl, e-propyl, /so-hutyi, n-fcuiyl, te/t-butyi, n-pentyi, 1-, 2- or 3-methylbuiyi, 1,1-, 1 f.2~ or 2,2-dimethyipropyi, 1 ~eth y! p ropyI, n~hexyi, n-heptyl, n-octyl, ethylhexyl, n-ndnyi, i-doGyl, n-undeoyl or n-dodecyl. The term “Aikyi” used in the toJioMog denotes a stmighhchaln or branched alkyl group having 1 to 12 0 atoms.

The substituents RCf are independently of each other preferably a straight-chain or btohched aikyi group having 1 to 4 0 atoms.

Ptofetohly n is 0.

The sobstitoeni R2 is preferably H or a straight-chain or branched alkyl group having 1 to 4 0 atoms. The subsfiiueni Rz Is particularly preferably H.

The substituentW isptotefably a straight-chain or b ran shed alky! group having 1 to 12 G atoms.

Post preferred benzimidazole derivatives are N-rhethyi-benzimidazole (NMB) and N-buiyhbermlrnidasole (N88),

The oieeftolyto tormulaflon as described or prefer ahly desonbed before comprises bonzlmidazoSe or benzimidazole derivatives as described or preferably described before in 1 to 20 wi% based on the total weight of the electrolyte formulation.

The electrolyte formulation as described or preferably described before .particularly preferably comprises benzimidazole or benzimidazole derivatives aadesoribod or preferably cfescribed before in 2 to 15 wt% based on the total welgbf of the afaotrslyfe formulation.

Benzfmidazoliurn salts: are Ionic compounds There Is in principle no restriction to the kind of anion.

Preferred benzimidazoityrn salts correspond to formula (II)

(H) wherein

Rs* is a straight-chain or branched alkyl group having 1 to. 12: C atoms vvhleb rosy comprise an 0 atom or an: S atom, n is 0, 1, 2S 3 004, R;\ Ft2' add are independently of each other H or a straight-chain or branched alkyl group having. 1 to 12 G atoms which may comprise an 0 atom or an S atom and An" is an anion.

The substituents R°' are independently of each other preferably a straight-chain or branched alkyl group having: 1 to 4 C atoms.

Preferably n is 0.

The substituent R'!" is preferably H or a straight-chain or branched alkyl group having 1 to 12 C atoms. The substituentH1* is pattlopiarly preferably H,

The substituent R2* is prsfemhly B or a siraightmhatn or branched group Having: i to 4 C atoms. The substituent R2> Is particularly preferably H.

The: substituent R3' Is preferably B or a sfra ight-chaίn or branohed alkyl group having 1 fp 4 C atoms. The substituent R3* is particularly preferably H,

The anion Arr is preferably ^ieptecf frora a halide ion, such as F\ do !*, a pofyhalsde Ion* a fiuoroalkanesulfonate, a fluoroaSkanecarboxyiatej f triCffiiopl^lkyisuifonyOmethlde, a bisiflubroalkylsulfonyOimirte, a a if file, a hexarkiorophosphaia, # fri-, bis- and Riono-Cflyoroalkyp tetrafluoroborate, a a tetracyanoborate, .{7)pp:0fjyerpidp^irtoboraf8| biflyorbdlcyanobpfafe, menohydrldcthoyanoberafs, rtlhydrldodicyaaohorate,; alkyltricyanoborate, a fhloeyapate, an aikyisulfonate or an tlkylswlfate, .with 1 to 20 C atoms* preferably perfiuorinaied, fluoroalkyl having 1 to 20 C atoms and alky! having 1 to 20 C atoms. Fluoroalkane or fluoroaiky! is preferably perfiuorinated.

The abibn Arr is partsoularly preferably an iodide, a tetracyanoborate. a rbphbfluomtri^ a dlSpoFbdfcyaooborate, a monoHpiridofrtoyaaot^mte* a dihydrtifortfoyanoborate or an afkylpiopnpbprate in which the alkyl group is straight-chain or branched haying i to 4 c atoms.

The mpst preferred benzimldapofium salt is benzimidazolium iodide.

Theeteetrofyte formulation as described or preferably described before comprises ^:sift as described or pfpferably described before in 0 to 5wt% based an the total weight of tbs electrolyte formulation.

The electrolyte formulation as described or preferably described before particularly preferably comprises a benzimidazafium salt as described or preferably described before in 0 to 4 wt% based on the total weight of the electrolyte formulation.

Within the electrolyte formulations -as desorlbod before or ps^rably described befera it Is further preferred that fhesum of weight percentages of the: benzimidazole or benzimidazole derivative together with the benzirnidazolium salt is at least 2 wi%.

The benzirnidazolium salts as described before or preferably described before a# preferably used together with i •benzimidazole in the stable electrolyte formulations according to the invention.

When using benzimidazole on benzirriid azole derivatives optionally together with benzirnidazolium salts in absence or in conjunction with omounisep fO;::t.§j:WtS'ibf'''furfner additives according to the invention, the eldctrblyfe;forrndiatiortjifoay aciditionally comprise: one or more organic iodides to generate the b‘/h redox couple together with:

Iodine,

The ^jNjp^slrolyteiiϊ«ιβρil:'comprises iodine (Is') lb |,b io 10 wt% based on the total weight: Of the electrolyte formulation.

The eleotrolyte formulation preferably comprises: organic iodides in 10 to 5Q wfli based: on the total formulation. The electrolyte formulatson particularly preferably comprises organic: iodides in i-5 to 45 wt% based on |bO; total weight:0f:the electrolyte formulation. ilia electrolyte formulation according to the invention may comprise o|e or more or§ anio Iodides, Preferably, the organic cations of the organic iodides are selected from 1.. 1 -diaikyfpyirolidinium, 1-alkyl-1-afexyalkylpyfrolldinjdm, l.d^iaiylliiifdagoltum, 1~aJkoxyaIkyt-3~ aikylimidazoiium and l-alkepyl^aikylimidazoflym. Preferred efehodimente of suchcations are described before.

Particularly preferred organic iodides are 1-efhyl»3-rnet^feid#^cildlB iodide (emim I), 1~propyl~3-methyiiniidazolsum iodide (proim I), 1-butyl4mrethyldmidazoliym iodide (hmirn I), l-hexyl-S· fhetbylirrtidazolium iodide (iimtm i), i ,3minfeihyMmidazo!lum Iodide (mmirn I), 1 yaliyieVmeihyNmidazQlmm iodide (amim h. N-butyi-N-meihyl-pyrrondinium iodide (bmpi 1) or N^M'-dirnethyPpyrioUclinium iodide: (mmpl I) or mixtums thereof. It is preferred to use a mixture of organic: iodides as described before. Very particular preferred ofginlb liodides are 1 s3~dimethyiimidazoiium iodide, 1-ethy!~3~ methyilmidazolium iodide and I propyi-S-methylimidazoitum iodide or mixturee tbereot

When using benzimidazole of benziniidazsfe derivatives optionally fogather wi% benziirfeazolium salts in absence or inconjunetion with amounts up to 0.5 wt% of further additives according to the invention, the electrolyte formulation may additionally comprise one or more solvents.

Organic solvents may he present in amounts of 25 to 70 wt%.

Organic eolvihfs. if present in such amounts as indicated above, may be selected from those disclosed in the literature.: Preferably, the solvent, if presenfj heeia boiling point higher than 160 degrees centigrade, more preferably higher than 190 degrees. Preferred solvents areacetonitdle, benzonlfile,: valeronirile, propylene carbonate, ethylene edrfoohate, butylehe carbonate, gamma-bufyroiaefone, gamma~va terolacfone, olutaronitrile, adiponitrile, N- metbyloxazoldihone, N-metbylpyrroHdinone, N,.N:,~:: dimefftflimy^ N.iN-Pinplhyiacelamiele, cyclic ureas preferably 1or 1s3»brmethyfc5,4 fetra hyd ro~;2f 1: H)pyrfmiriSnone, plymea preferably tatragiyme, sulfolane; sultanas which are preferably asymmetrically substituted suph at ^rplhanssulfonyi-propan^p^ethanesyffonyhSyrTipthyb: propane or 2^r©p-an^»sii^sfiyi}-biitao%;.s^^0i^ft&amp;, hpfhylsilfplapo, 3-methyisu!f0!ane, dirnethyisulfoxida, trimeihylphosphafo apO methoxy-substiiuteci nitriles. The preferred: soiyentislyfldlene^ 2~rnethyisuifolane or 3-meihyisu|folaoe>

In a preferred embodiment of the invention iheefectrDiyi© formulation consists of the described components, ^ie to an electrolyte formulation consisting of (I) 4 to 25 wt% of an looic compound having cyanoboraie anions; (il> 3.5 to 10 wt^ iodine; vsiu rD to SO wtbf.· of one or more Iodides haying ah organic dafiph·:: (iyf: 1 to 20 wf % of ben^i^idazole or a benzimidazole derivative of formula (I)

f wherein H! are indep^g^y ofeach ^ gtrai^hi-shaln or brarrched alkyl group having 1 to 12 € atoms which may comprise an O atom or an 8 atom, n is 0, i j 2; 3 or 4 and R2 is H or a straight-chain or branched alkyl group having 1 tp 12 C atoms which may comprise an O atom or an S atom; (v) D to. 5 wt%. of a benzimidazolium salt; :(vl) 0 to 0,5 wt% of further additives and (vti) 25 to 70 wf% of one or more solvents, wherein the amounts in wt% are based on the total of the formulation,

Preferably: the invention relates to an electrolyte formulation consisting of (i) 5 to 2d wt% of an ionic compound: having cyanohorate anions, (li). 4: to rwt% iodine; (ill) 16 to 45 wt% of one or mor@: Iodides having an organic cation; (ly) 2 to 15 wl% of benzimidazole or a benzsmldazQle derivative of formula (I)

(!) wherein R° and R1 are independently of each sflior a sfralgNttoham or branched; alkyl group liaving: 1 to 12 C atoms which may comprise an O atom or an Si atom;, n is 0, "I; 2, 3 or 4 and R2 is H or a straight-chain or branched alkyl group bawng 1 to 12 G atoms which may comprise an O atom or an $ atom; (y) 0 to 4 wt% of a benzlmldazolium salt:; (vl) 0 to 0,1 wt% of further additives and (vli) 46 to 65 w!:% of one or mors solvents:, wherein the amounts in wt% are based Ion file fetal of the fpfnulafion. the sum of weight percentages of the benzimidazole or benzimidazole 'derivative together with the benzimidazclium salt is at ieast 2 wt% in the above described specific electrolyte formu lotions.

The ihveotion '.therefor#1 'related %; these.; specific· formulations consisting of the: desehbed components wherein the euro of weight percentages of the benzimidazole or benzimidazole derivative together with the henzimidazoilum salt is at least 2 wt%.

Ai l preferred or particuiar preferred embodiments of the ionic compounds having oyanoborate anlenSi the further additives, the organic iodides, benzimidazole derivatives, benzimidazoiium salts and the solvents alone or in combination as described before apply accordingly for thesespecific electrolyte formulations.

The Invention therefore relates to these specrio electrolyte fermuiaiiohs consisting of the described components wherein the further additives are alkali metal Iodides and/or thiocyanate salts.

The Invention therefore relatesTo these speclfc electrolyte fermufaldns oonsfeting of the described components wherein the: further additives are lithium iodide and/or guanioinlum thiocyanate and/or t-ethyb3~mefhyljmid@^

The invention therefereTel|tes to these specific electrolyte formulations consisting of the described com portents wherein the Ionic compounds having oyandborafe anions afe ionic compounds having anions selected from the group consisting of monohydndotrieyanoboate and dihydridodioyanoborate,

The invention therefore relates to these specific electrolyte formulations consisting of the descslbed compenenfs wherein tho ionic compounds having cyanoborate anions has an organic cation fh^riil |he group comprising sulfonsum, oxon lurry ammonium, phospbontym, uranium, thlouronsum, guanidlnium cations or lieferopyeiie cations. the [nvention therefore relates to these specific electrolyte fpmigiafiorts consisting of the described components wherein the one or more solvent is selected from acetonitrile, benzonitriie, valefonitrste, propylene carbonate, ethylene carbonate, butylene carbonate, garnma-butyrolacione, gammaweieralactone, pitteronitdiej adipenitrfle, N-mefiiyloxazoNdinone, N~ mefhyipyrroi'sdinone, N,Ncdsmethryllmidazo'iidinone, N:fw dlmelhylaoetamldei 1 ;3-dlmethyl-2dmidauoila'inone, 1 i3^^-i-iS.^^tetrahydΗ)~^!Γ|^;ίί!^|^οη:ΐθιί tetraglyme, sulfolane, 2~ eth driesuifonyhprepane., 1 -οίηβπβδηΙίοηνηίνοθίηνΙ-ρΓορβηο, 2-Ipropane-S^solfeny^hutane, sulfelanej 2-methylsuifPlape, 3~ methyisuifoiarse, dimethyisutfpxide, trimethylphosphate and meihoxy-· substituted nitriles.

Padieuiariy preleraply, the IriventiQri relates to an electrolyte formu fatfori consisting of (i) : S to 20 wt% of an ionic compound having hydridetrfoyanpfcoraie or dihydridpdidyanoborafe arfiens; (ii) 4 to 8 iodine; (iii) 15 to 45 wi% of one or more iodides selected from 1 -ethyi~3-· methylsrhidazoifum iodide, 1~propyb3~methylimidazoiiuni iodide, labutyhS-metbyhimidazoliusii y-i mefhyitriiidazoiiUm iodld% 1 ;3"dimethyhimidazoiiurn iodide, 1~ a||yi~3neethylimidazoiiuin iodide, ^yiroildlriSum-'iodide (iv) 2 to 15 wt% of hesizimidazoie or a benzimidazole derivative df formula (1}

(i) wherein R.° and W a re Independently of each ether a straight-ohairi or branched alkyl group having 1 to 12 C atoms which may comprise an O atom or an S atom, n is 0, 1, 2. 3 or 4 and R2: Is R or a straight-chain or branched alkyl group having 1 to 1.2 C atoms which may comprise: an 0 atom or an S atom; (v) Q to 4 wt% of a ben^mldazoiium salt; {y i) the sum of weight: percentages of the benzimidazole or benzimld azole derivative together with the benzlmidazcliurn salt is at feast 2 wt%; (vii) Q to 0.1 wt% of lithium iodide, guanidinium fhiocyantate or 1 -ethyi-3-methylimidazoiuni thiocyanate and (vilj) 45 to 55 wt% of one or more .solvents, wherein the amounts in wt% are based on the total of the formulation, preferably sulfolane, 24hethyi~sisifolane or 3~methyi-suifoiaBe.

Very partlpufarly preferably, the invention relates to an electrolyte formulation: consisting of p): 5 to 20 wf% of 1 -eihyl-S-methyibenzimldazolium monohyd rid otricya n oborate or 1 ~ethyi~3~ methylhenzimidazcdium dihydridodicyanohorate; (if) 4 to 8 wt% Iodine; (ill) 15 to 45 wf% of one dr more iodides sdlested f om l-ethyl-S-methytirnldazolium iodide, 1~propyl~3-methyHmidazollum iodide add 1(3~dimethyl~imidaz;oii:U:m Iodide; {IV) 2 to 15 wt% of benzimidazole, N-methyltoenzimidazole or N-· butyl-feenzimidazote: (v) 0 to 4 wt% of a benztmidazoiiym iodide; (vi) the sum of weight percentages of the benzimidazole,: N~ methyl-benzimidazole or ht-butyld^enzit^idazole: together with feehzimidazpitum iodide is at least 2 wt%; (vi?) 0 to 0:1 wfS of lithium iodide,, guamdinium thiocyanfate or 1- ethykS-methylimidazolfum thiocyanate and (Vi) 45 to 51 wt% of sulfolane, S^methyi-snifolaoe or 3-methyl" sulfolane,:

The amount of 15 to 46 wt% of one or more Iodides selected from 1-ethyt-S-methytimiiazollum Iodide, 1 -progyl»3-methylimidazolium iodide and 1,3-dimethyi-lmldazollum Iodide may be achieved through δ to 40 wf% of 1 -8ihyl“3-methyii.midazoltum iodide, 0 to 40-:wt% of 1-. propyl-S-methylimidazoiiorn iodide and/or 0 to 40 wf% of 1s3-dimethyMmMazotiu no iodide.

When using a benzimidazole derivative such as N-methyfbenzimldaoie or N-butylbenzimidazole, It is preferred not to use a benzlmldazolium salt In the electrolyte formulation: resulting in an amount of 0 wt%.

It is mostly preferably that the electrolyte formulations according to the Invention pro in the absence of any further additive as described or preferably described.

The most preferred electrolyte formulatens according to the invention are the electrolytes 15 and 1? as described In the examples below,.

The process for manyfacturfng the electrolyte formulations according to the invention is 'known in: the art and is preferably done by mixing the specific components as described or preferably described before. eieeitolyt#formulations according to the Invention aro hP^rsfoly used In opt0etectc<|inie;:dev.i^^

The optoelectronic device according to the indention include, without lirhitation, a solar ceil, an optical detector, a photoreceptor, a photodiode, a photomultiplier, a photo resistor, a photo detectorr a iightsensitive detector, a solid-state Mode, a transistor, an igtogratod circuit, a field-quench device, a light-emitting device, a laser, a laser diode, a piasmon emitting device, an electrophotography device or a wave convertor, [Λβ term solar cell is known in the art as a:;:de¥(ee: converting shy kind of light into electricity. The term solar cell includes a photovoltaic cell, A preferred solar cell Is a dye-sensitized solar cell, A transistor inefydas a phototransister, a field-effect transistor, a thln-fflrn transistor, a fight-emitting transistor. A light-emitting device Includes an electroluminescent device, a phofofemfhesoerit device, a bioluminesceni device and a light-emitting diode.

An electroluminescent device includes a iighlpemitting eieGtrdchdrnical pell A iasir includes A diode injection laser.

The an optoelectronic device comprising an electrolvte formulation as described before or preferably described before which is a solar cel an optical detector. a photoreceptor,..a photodiode,: a photomultiplier, a photo resistor, a photo detector, a lightsensitlve detector, a solid-state diode, a transistor, an integrated circuit, a fieid-quench device, a light-em|tong device, a laser, a laser diode, a piasmon emitting device, an electrophotography device or a wave converter.

The preferred device according to the Invention is a solar eefi.

The particularpmferred optoelectronic device accprding to the invention 1$ a dye-sensitized solar cell.

In dye -sensitized solar ceils, a dye is used to absorb the sunlight to convert Into the etectricai: energy. There are no restrictions per se with: respect to the choice of the dye as long as the LUMO energy state is marginally above the conduction bandedge of the pholcefeotrode to be sensitized, Examples of dyes are disclosed in EP 0 986 070 A2, £P 1 180 774 A2 or EP 1 507 SO? A1.

Preferred blue dyeO Cbrresf ond to formula (1)

wherein R and R*in formula (1) are independently of each others straight-chain orbfs^ed alky!group having 1 to 12 Catoms,

Ri and R2 in formal 0 ) are independently of each other Hs a straight-chain or branched alkyl group having 1 to 12 C atoms or Rt anCi R8 R4 and Rs in formula (1) are independently of each other H; a straight-chain or branched alkyl group having 1 to i&amp;-&amp; atoms*, a strafe ht-chain or branched alkenyl group having 2 to 12 C atoms or an ary! groups^ having 8 to 12 C5 atoms which may be substituted, n is 0 or 1, m is 0, i, 2, 3 or 4:,

p Is 0:1 or 2S m+p is 1, 2, 3. 4, 5 or 6, and/or salts. tautomers, stereoisomers and/or solvates thereof,

Preferred dyes are organ!® dyes such as IV1K-1MK-2 or fviK~3 (Its structures are described1 in figure 1 .of N. Koumura etal J,Am,Chem,Soc. Yot 123, ho.44, 2008. 14256-14257), D102 (CAS no,. 352145-28-3), D-149fCAS no. 733843-20-7), P205 (CAS no,, 938338-21-9), Q3S8 |CAS: no. 1207838-53-6), YD-2 as described in T. Bessho at ai, Angaw, Chem, Inf. Ed, ¥ol 49?: 37, 6848-8345, 2010, Y123 (CAS no. 13124:65-92-1), bipyridin-Ruthentum dyes such as M3 (CAS no. 141460-19-7), N71S (CAS no. 207347-48-4)., Z907 (CAS 00, 6.02:893-09-8), 0101 (CAS no, 1:048984-93-7), 0108 (CAS no. 1152310-8:5-4), K19 (CAS no. 847665-45-6), HRS-1 (CAS no. 906061-30-1 as disclosed ίο K J. Jiang et a), Chens, Comm. 2460, 2006) or ter|5yrfd:in@-Rutr®niur«:dy«.s such as Μ74Θ (CAS no. 359415-47:-7).,

The structure of D285 is

The structure of D358 is

Preferred' blue dyes am the dyes {1-1} and {1-2):

including salts, tautomers, stereoisomers and/or solvates thereof. particularly preferred dyes are Z90? or Z9Q?fs|a which are both an gmpNphld ruihe^ or HRS-1. The dye ^gQTNa means NaRu(2>2:4;ipyridine'-4--€arboxylic acid“4!-caibo4yidte|f4,4dde^ partieulariypreferred dyes are Z907 or Z907Na and/or 0358. Very very particularly preferred dyes areZSOT or Z907Ma.

The dye l9Q?Na means Na Ru(2S 2’-bipyridtne-d-earhoxylic 3019-4-carb0xylate)(4)4'-dlnonyh2!2'-blpyndiSie}(NGS)2.

In a preferred embodiment,.the.dye is ooadsorbed.

There arem. restrictions: per se with respect to the co-adsorbent in the optoelectronic device adcerdidg to thednyentlbn.

Suitable co«adsorbentsare described, for example, in GhemSueCherd 2915, 8, 888 - 599. A suitable co-adsorbant is, for example, ehbfio acid (CA), deoxychofic acid (D€A): ursocIeoxycholic acid (UDCA), chenodeoxychoiic acid (CDCA), dydqpen^iaoetic acid |BPEAA), 4~guanid inobutyric acid (6B.A), 4-aminobufnc acid (ABA), but^rfc ^eid, 0etaa0ic:addi:iaude add, stearic add, 3:3,3-iripttiii^propiioniG add, pivaiic acid, citric acid, S^-dttNopropionic succi n ic acid, 3,4,3~tris{dQdecyioxy)benzoic acid, hexadscylmaionic add, phenylmalortsc acid (PMA), isopropylmaiooic acid, n-butyimatedtc acid, cydopentyimafenic add, phenylmalonic acid. benzylmaionic acid, cyclopropyiacetic acid, cydopeniyfacetic acid, cydodcKyiacatlc apid, tert-buiyiacetic acid, 1~naphf.hyiacetic acid, cydd^eptyiaceic acid, 4-padidihDbittiric acid, 2~phenylethano|C acid, S^pheaylproaicaic acid, 4~pheny::butyric acid, S-phenylpentancic add, acid, i|is-0f-3-<|tryrath:yi«byty:i| phospMnid |ddi neohexyS' phosphoric acid , phenyiphosphonle add (PRA), phosphoric acid tn-ethyi ester (PATEE), phosphoric acid trPbuiylester (FAJiBE}, 1*dpcylphcsphonic:ac|drfpPA);, dibaohfKyi blsC3,S~ dlmetbyibyiyljphcspbihic aoidllliNBQP).: dipCeoyiphosphinic acid (PFPA), acid (81V1PPA}, bis(2- ethylhdxyl) phosphide add, 4-N,M-dimethylaidnopyridine (OyAP). tefebytyiarprnoriiym isoaicotinate (T8Ali% methyilsonicotinate (MiN), 3idienyi-2t4-penianediohe, 3-btrfyi''2,4-perdansdiorse, acelyl acaieme, RubcterpyHNQSIsTBAs :(tctefpy ™ 4i4\4,!4ricarboxy'' TBA ~ tetfahuiylammofilum}, 4-(bis(9:9-d!rnethyP3H-ffd0tep~2^ acid {2~ethyib8Kyic3xy}phenyi]-9H-carba~zol~9--ypenzoicacidt 4-(0^3(9,9-dsmethyl~9il4iuoren-'2~yl)anilno)-1-naphthoic(HC''A4}1 acid, i^tfaethpxypliapp: (TEOSI, phenyitnefhoxysiiane (PTEOS). 3~ (triatboxysliyi)feran, i^-foisitrietboxysilybbeazeae, 1,3·· bls|t;riefho?i;y8ii^ (3- iT#ftseptpp^ trieth oxy-3~(2 - i rn idazoi i η-1 ~ yt)pmpyisiianeV':c^®ydcde3ddrii: p-rjyclodoxdria and γ-cydodexdrin. A p^laff^/c^daibrl^htls^oxychclic acid and/or-d»cydodexdp, A padloolar preferred co-adsorbent is deoxychoiie acid, A preferred example pf a phesphjpic acid is Pis(3,3feimetbyPbutyi)-phosphinic acid (D1NH0P} as disclosed in M.. Wang etai, Daiton Trans., 2009, 10015-1:0020. f orexample, a dye^sensifised solar cell comp rises a photo-electrode, a esunferalectrode and, between the photo-electrode and the counter electrode* an electrolyte formulation or a charge transcoding rnaterial, and wherein a sensitizing dye is absorbed on the surface of the phcto^ecirode, f n :|he side facing the counter electrode.

According to a. preferred embodiment of the device according to the invention, it comprises a semiconductor, the electrolyte formulation as described above and a counter electrode,

According to a preferred embodiment of the Invention, the semioondoptorls based on material selectedfram the group of Si, !Kk: SnOs, FecOs, WOa, ZnO, Nbi.Os, OdS, ZnS, PbS, BfeSs, GdSe, Gap, InP, G|Ass 0dT^:( Cuin%; and/or OuinSeg; Pifferably, the s#rb|b#dboiir-dohiprfses:.a. mesoporous surface, thus increasing the surface regionally covered by a dye and being in contact with ibe efsotrotyfe,

The semiconductor'f IGs may contain anatasedype crystal structure Of preferably 70 volume % dr more, particularly preferably 100 volume '?M.It ispreferable that the semiconductor is doped: With a metal to increase electron conductivity thereof, This mete! is prefembly mcnovaient, divalent or bivalent PMsj^ly,''^:i^ibQndud^ris^rea0^:<>rii a glass support or plastic or metal foil. Preferably,"the support is eonductlve.

The semitlzed metal oxide electrode to foe used in the device according to the invention may comprise an electrically conductive support, the photosensitive layer containing the sensitised metal oxide seeoitlifig to the invention as described or preferably described before and an yndeiaeling layer between fee photosensitlvelsyer and the conductive s upport.

The:: sensitized metal oxide electrode preferably comprises an eiecfndplly conductive support, the photosensitive layer Containing: the sensitized metal Oxide according to the invention and optionally an undercosfing layer between the photosensitive layer and the eondbbd Wsu pport

There ore no restrictions per se with respect to the conductive support of the sensitized metal oxide eiectrode according to the invention,:

The conductive support-may foe composed of a single iayer of an eiectricaliy conductive material or of two layers of an electrically conductive material and a substrate.

Prafemble examples of the electrically conductive material include matalssuoh ae platinum, gold: silver, copper, zinc, titanium, aluminium, indium and alloys composed thereof; carbon; conductive polymers such as PEDOT; eietrtr|ea% conductive metal oxides such as indium'rtin composie oxides and in oxides doped with fluorine or antimony. VVfoen light is irradiated from the conductive support side, I Is is substantially ttansp;a:ren|

Herein, the term -substantially transpardhf meansIblt the;liglit transmittance is W% or more to a light In visible region to near infrared region. The light: tensmlftahoe ^ δ()% or more, more preferably B0% or more, The conductive support particularly preferably has high iight transmittence to a light that the photosensitive layer has sensllvityTb,

Suitable·transparent subsirafes are glass or transparent polymer films.

Suitable glasses are low-cost sceta glass ns mn-alhafi glass that causes no alkaline elution.

Suitable· polymers within the polymer film are tetraoelylcelfitlos© (TAG), polyethylene ferephthaiate (PET), polyethylene rmphihalate (PEN), syndlofactle polystyrene pPS), polyphetiylenesulfld© (PPS):1 polycarbonate (PC); polyabrylafe (PAry pplysulfone (PSF), polyestersulfbne (PES'y polylmlde (Pi}> polyestedmide (PEI). cyclic polyolefin or brominafed phenoxy resin.

The conductive support may comprise metal leads. The metal lead is preferably made of a.metal such as platinum, gold, nickel,, titaniyny. alumidiitm, copper or silver,

The preferable electrically conducive material Is fin dioxide doped with fluorine or antimony or indium-tin oxide (ITC5),

The preferable transparent conductive support is tin dioxide doped with fluorine or antimony dr Indium-tin oxide on glass or plastic substrate.

The preferable opaque conductive- support is tin dioxide doped with fluorine or antimony or indiurn-tin oxide on metallic substrate such as titianium or steel or glass structure.

There are no restrictions per se with respect: to the method of sensitization:.

The dye or a mixture of dye with co-adsorbent may be adsorbed to the metal oxide by soaking the conductive support containing the well-dried metal oxide layer; to be sensitized in a solution or by permeating the conductive support containing the well-dried metal oxide layer with a flow of a solution.

In the former case, a soaking method, a dipping method, a roller method, an air-knife method may be used. As an applying method of the latter case, a wlre-bprmefhodl· a slide-hopper method, an extrusion method, a curtain method, a spin method or a spray method .may foe used.

There are ho restrictions perse with respect to the counter electrode co:rapHsed:in'th0/pP^oiootfo:pio device according to the isye?ltipr&amp;·

The counter electrode Is the counter electrically conductive layer, which is supported by a suhslrate, if necessary. Examples of electrically conductive material used for the oouhter electrically conductive layer include metals such as platinum, gold, silver, copper, aluminum, magnesium and Indium; carbon;conductive polymers such as PEDOT; and electrically conductive metal oxides :;:such as iodfdmttin composite oxides, and fluorine-doped tin oxides. The suhstratirdf the counter electrode is preferably made of a glass or plastic as described before. The counter electrode may be a mesh electrode,

Preferably, the counter electrode Is an electrode consisting of platinum, gold: silver,: copper, aluminum, magnesium or FEDOT,

The device of the present invention may be manufactured as the corresponding device of the poor art by simply replacing the electrolyte by the electrolyte formulation of the present invention, For example, In the case of dye-sensitized solar cells, device assembly is disclosed in numerous patent ierafura, for example WO 91/18719 (examples 34 and 35), but also scientific literature, for example in Barhe, G.J,, Arendse, F.t Comte, P.. Jlrousek, M,, Lenzmana, F., Shklover, V„ Gratzel, M. J, Am, Geram, Son. 1997, 80, 3157; and Wang, P.. Zakeeruddin, 8. ML, Comte, P., Charvef, Rv, Humphry-Baker, R, Critzel, M. J, Phys. Chem. B 2003,107,14336;

One suitable embodiment is a process for the manufacture of a device according to the invention as desdrihdd hetdre or preferably described before comprises the steps of - providing a dye-sensitized metal oxide electrode as a first electrode; - providing a counter electrode as a second electrode; - assembling the first and the second electrode through sealing and building an internal space d between the electrodes and - fitting the distance d with the electrolyte formulation as described before or preferably described before.

The distance d is the distance in pm between the first electrode and th§ second electrode. in another suitable embodiment, a process for the manufacture of a device according to the invention as described before or preferably describee before comprises the steps of - providing a hon-sensitized metai oxide electrode as aJrsf: electrode;; - providing a counter electrode as a second electrode; - assembling the first and the second electrode through sealing and building ah infernal space d between the electrodes; « sensitizing the rnetal oxsdewith a sensitizing solution comprising the dye; cleaining the sensitized metal oxide with a cleaning solution and ~ filling the. distanced with the electrolyte· as described before or preferably described befdm,

The device according to the Invention asdescribed before may be part of a hi alii junotion device or be pad of a module, Μ wlf:he^ that variations to ihe foregoing embodiments of the Inventiori sen foe made while siillfaSlihg v^ithin the scope of the invention, iaoh feature disclosed inthisspeeificafion, unless stated otherwise, may foe Mpiaced hy aitemaiive features serving the seme, eqyivaient or simitar puipose. Thus, unless stated otherwise, each feature disclosed is one example only of a generic series of equivalent or airntier features.

All pf the ifeitares disolosed in thisspecificatlon may be combined in any combination, except combinations where at least some of such features and/or sfepsere mutually exclusive, In particular, the preferred features Of die invention are applicable to all aspects of the invention and may he used in any combination, Likewise, features desferihed: in non-essential combinations may be used separately (not in comfofnatiohl.

The invention will howbe described In more detail by referent to the following examples, Which are iIIusfrative only and do not limit the scope of the invention.

Examples:

Within the examples, the term “electro iytes” is synonymously used for "electrolyte formulations”.

Divide EabrifeaSop andtostmg condition The dye sensitized solar cells commercially available from FhG ISE finstitut farsolare Enefgiesysteme, Freiburg), fabricated based on the disclosure of US 5f72d,4S7 or W02007/093961 and composed of 5 indiylduete and electhcaily Independent cells. Each cell included two layers of different titaniumdioxlde paste available from DyesoL namely DSL 18 NRT (two printed layers to obtain a final layer of os, 7 pm) and DSL 18NRT AO (one printed layer to obtain a ea, 4 pm layer) on a first fiuonnated finoxide substrate and a. printed plaiinium counter electrode(Platinum from iDdNiano, Pi-105020511} on a Second fiuonnated tinoxidesubstrate resuiting atypical cell gap (distance between titanis to Pt electrode) ofca. 7 μηι. The ceils are irrigated with a solution of 120 mg of Zi07 dye (available from SigmaAlcfrich, Ru(21Tmipyriclyt~4/T<ticarboxy!icacid)(4/d''dinonvi'· 2.2:-bipyridine)(HCS)·;) in 230 ml of ethanofifer 16-17 houraitunee with acetonitrile for an additional 15 Minutes and dried in vacuo for 80 minutes. The eiedmlyte formulations as described below are filled Into the interval space of the prepared ceils. The ceils are subsequently sealed with an UV-cure. glue (Lootits 350) and a 9 mm (diameter):χ·0,:12 mm (thickness) borosiSicate glass cover using a UV LED 4:Q0~pointiSmp Tom Dr. Grobel, UV Eiekfronio GmbH at set at 3$5:nm:PW/em?) for 49.4 sec. Each cell has a 2,5 cm2 area (5 mm x 50 mm).

Generic device measurement 1 he pbotocurrent and photovoitage curves are determined using a solarsimulater Sun 2000 (model 11018) frorriAhel Technologies and a Keith ley 2801A sduMemeter Whilst cooling the bask of the device using a Peltier cooler set to 25 X under 1 sun illumination (Aid 1,5G cailbraiecl td os, 995-1005 W.nrT Each cells are covered with a black photomask of 1 mm x 50 mm area. Power conversion efficiency (q or RGB) is oaloulated using ihe following expression

where Pis is the power of the incoming light, Voc is the open circuit potentiai J^ is the short cirsyit current and FF is defined as

where VmaTls the voltage at tlie maximum power point and Jma* is the current at the maximum power point.

For thermal ageing, the cells are placed into ah oven at 85 °C without humidity control. The sell performance is measured at regular interval (day 3, 4, 6, 10.17, etc,) by taking them out of the oven and cooling them to 2S X. The Tao thermal value represent the estimated time required! to obtain 80¾ of the initial power conversion '.efficiency determined at day 3.

For the light soaring ageing, the sails are placed into a Bolixan A-45 from Solaronix, Switzerland The devices are cooled to 25 X whilst under illumination to ca, Tsun '{AM 1,50, ca. 1000 Mny2)- Prior to light soak, the devices, the cells are subjected of the thermal stress at BS X for 72 hours to ensure the cell sealing is working as intended. Afterward, the ceil performance Is measured at regular interval (clay Q, 1, 4, 7,10, etc.) by taking them out of the light soaking chamber for ca, 10-30 minutes. The Tes light; soaking value represent the estimated1 time required to obtain. 80% of the Initial power conversion efficiency determined at day 0,..

The following eiectroiytas have been prepared.: All chemicals are sourced from Merck KBaA or 8igma~ASdrfeh,

* Not according to this invention

ΈΜϊΜ ~ 1 -eihyί-3 -rneth y Nm o 5 i 1.¾ m 1 * ts3~€llmeihyiimlcJazoiium iodide EMIM I' ~ 1'-e!hyi--3-rneih^limidazofiym iodide NBB « N-butyibenzimidazoie GOA SON ~ guanidinium thiocyanate

EfVIIM MNS - 1-ethyl-Suriethyiimidazoiiurn hydridoinoyanoborate. DSSG device odaracteristies for eleofrolytes are shown id Table 1,.

Table 1, Photovoltaic cell characteristics obtained under 1 sun illumination (Alvi 1,6Gt 100 73 mW.enr2),

* Mot according to this invention

As one cad conclude from the above example:, electrolyte 4 and 6 with extremely low amount of guanibiniumthioeyanateshow surprisingly increase: thermal stability (e.g. higher I® Thermal value) cempamd-fo· electrolytes 1 to 3 with higher amount of guanidmtum thiocyanate whilst demonstrating eguivajent power conversion efficiencies, A) Eleefrofyt# Freparaflon

The following electrolytes have been: prepared,. All chemicals are BOMfeePTropyeroh KGaA or Sigma-Aldrich, pphzlmliazoilum Iodide (81,HI) is prepared os followed To an ethanol sdlufion (50fern3) of pphiareldazote (3tT4f:, 0.300 otol) is added dropwise a solution of iodic acid (38.4a, 0,30 mol, 57 %) and sirred: for 2 hours at 23 *C, The solvent is completely evaporated and 103 cm3 diethyl etlier added. The residue Is filtered and washed with 4 x 50 cm3 ethyl acetate and 3x100 prtl3 diethyl ether. The product dried under high vacuum at 2380 yielding 46.0 g (62.3 %) of the title product, ΝΜΕ:{1::Η, CDsCN); δ 10,88 (hr, 2% 8.73 (s, 1H); 7 87 (m. 2H); 7.51 (m, 2H).

Not according to this invention;

EMM ~ 1 -ethyi-3-methyiimiazoilun·) ΜΜΜ I * 1,3-dimethy iimidszoiium iodide £MM f« 1-^h^!"3~mefhyiirnlclazoifurn iodide BS 1-benzimidazole BI.HI ™ 1 “benzlrnidazoliym Iodide: EMIM SON « 1 -ethyl-S-mathyiimidszoiium ihlQcyariate MHB ™ 1 “ethyi-3~mef^yffmsdazolsym bydrsdotrieyanoborate. B) Dev see lest DSSG device characteristics for electrolytes are strewn In Table Z Table 2. Photovoltaic ceil characteristics obtained under 1 sun iumfnatisrs (AM 1,56, 100J3 mW,enr2}.

* Not according to this ihvehtion Example 3 A) Electrolyte Preparation

The following electrolytes have been prepared. Ail chemicals are sourced from Merck K6aA cr Sigma-Aldhch,

* -'Mot according to this invention B) Device lest DSSC device characteristics for electrolytes are shown in Tstife J,

Table 3, Photovoltaic ceil characteristics obtained under 1 sun illumination (AP 1 ,SG, 100,73 mW,cnr2),

* Not according to this invention

As one oars conclude from the above example, 1) Electrolytes 9 to 17 without gyantdinium thiocyanate show surprisingly equal or greater power conversion efficiencies compared to electrolytes 1 to 3 containing guanidlteum thiocyanate whilst demonstrating higher' thermal siabOity (e.g, higher T80 thermal), 2) High concentration of alternative SChl salt {e>g, ΕΜΙΜ SC.N m Guo SON) oan enhance In: some cases the thermal stability #<§, higher T80 thermal) as shown with devices made of electrolytes, 6 fo 8 and 18-21 hut the power conversion efficiency are significantly lower compared to devices using electrolytes 8-17,

Devices containing electrolytes 15 and 17 show significant increase of the light soaliing stability (e,g. Tso iighf soaking) compared to devices' containing electrolytes 8 to 8 and 18 to 21 which include SC hi salts.

Claims (12)

1. Patent Claims 1 >: Use of benzimidazole: or benzimidazole derivatives optionally together with banZimibazoliurn salts in electrolyte formolatbns comprising iodine Irt at least 3.5 wf% and cyanoborate anions in absence or tn conjunction with amounts up to 0.5 wt% of further additives where ail weight percentages are based on the-total weight of the electrolyte formulation, 2-, lisa according to claim 1 wherein the further additives are alkali metai iodides and/or thiocyanate salts.
2. 3, Use according to claim 1 or 2 wherein the further additives are lithium iodide and/or gyahidiniurn thiocyanate and/or 1:~ethyf*3» methyilmldazoilum thiocyanate,
3. 4, Use according to one or more: of claims 1 to 3 Wherein the ionlo compounds: haying cyanoborate anions are ionic compounds; having anions selected from the group consisting of tetraeyanoborate. monofiuorofncyanohorate, bifluorodicyagoborate, monohydddotncyanoboraie, dihydndodioyanoboraie or aikylfrioyanoborate in which· the; alky! group is straight-chain or branched having 1 to 4 6; atoms,
4. 5, Use according to one or more of claims 1 to 4 'wherein the benzimidazole derivatives are compounds of formula (!)

   (!) wherein Rc and R1 are independently of each other a straight-chain or branched alkyl group having 1 to 12 0 atoms which may comprise an D atom or an S -atom, n. Is 0:1, 2, 3 or 4 and R2 is H or a straight-chain or branched alkyl group having 1 to 12 ¢5 atoms which may comprise an O atom or an S atom.,
5. 8, An electrolyte formulation consisting of (i) 4 to 25 wt% of an Ionic compound having oyahoborate anions' (ii) .3,5 to 10 wt% iodine; (Hi) 10 fa 50 wt% of one or more iodides having an organic cation; (iv) 1 to 20 wt% of benzimidazole or a benzimidazole derivative of formula (I)

   (i) wherein and R1: are independently of each other a straight-chain or branched alkyl group having 1 to 12 Ό atoms which may comprise ·βη O atom or an S atom, n is 0, 1. 2. 5 or 4 and R3 Is H or a straight-chain or branched alkyl group having 1 to 12 C atoms which may comprise: an O atom or an S atom; :(v) 0 to 5 wf% of a behzlmldazolium salt: (Vi) 0 to 6S v$% of further additives and (vii) 25 to 70 wt% of one or more solvents:, wherein the amounts, in wt% are based: on the total weight of the electrolyte formulation, -An.:ele^fQiyt« formulation according to claim 6 consisting of (I): δ to 20: wt% of an Ionic compound'.having. fiydildpeyanehoFate anions; {if) 4 to 8 wt% iodine; (ill) I S to 46 wt% of one or more iodides having: an organic cation; (iv) 2 to 15 wt% of benzimidazoie or a benzimidazole derivative of formula (1)

   jfl) wherein R0 and R1 are independently of each other a stralghbchaln or branched alkyl group having 1 to 12 C atoms which may comprise an O atom or an S atom, n Is 0; 1. 2. 3 or 4 and R2 is H or a straigSihchain or branched alkyl group having 1 to 12 0 atoms which may comprise an O atom or an S atom; (y) 9 to 4 wt%: of a bsnzlmidazollum salt; (vi) 0 to 0,1 wt% of further additives and (vil) 46 to 66 wt% of one or more solvents, wherein the: amounts in wt% are based on the total weight Of the formulation.

   8. An electrolyte formulation accordino to claim 6 or 7 wherein the sum of weight percentages of the benzimidazole or benzimidazole derivative together with the benzimldazefium salt is at least 2 wt%
6. 9, An electrolyte formulation aoeording to one or more of claims § to 8 wherein the further additives are alkali metai iodides, and/or thiocyanate salts.
7. 10, An electrolyte formulation according to one or more of claims β to 9 wherein the further additives arc (ifofofoilDdid^^ihdfor guanldtnibra thiocyanate:and/or 1~ethyl3Amethy!imidazoHurn thiocyanate.
8. 11, AneiecMyte formulation according to one or more of claims 6 to 10 wherein the ionic compounds having eyanoborate anions are ionic oombounds:hewing anions selected from theiiWp consisting of pfnbHydri^ and: dihyd ridod icy an ©borate.
9. 12, An electrolyte formulation according to one or more of claims 6 to 11 wherein :f bp ionic compound having eyanoborate anions has an organic cation selected from the group comprising suifonium^oxoniurni ammonium, phosphonium, uronlum. fhiouronium, guanidinium cations or heterocyclic cations.
10. 13, An electrolyte formulation according to one or more of claims δ to 12 wherein the one or more solvent is selected from acsfopiirilfo bonzonitrilo.valeronitriie^propyfene carbonate; ethylene carbonate, butylene carbonate, gamma-butyrolactone, gamma-valerolactone, gtutaronitrile, adiponitrile, N~ methyloxazoSidinone, N-mefhylpyrrolidlnone, N,N-dimethylimidazolidinone, N.N dlmethylacetamide, 1 .Sfoimethyl-a-irhWazoiidlrioney 1 (3foimcfhyl~3!4t§t6-'tefranydro*2(1 H}~ pynmtbinone, fefragiyme, sulfolane, ^-ethanesulfonyl-propane, 1 -etflar1esulfonyA2-methyl·ρropanet 2~(propane-2~suIfohy !}fou tone, sulfolane, 2-mefhylsMlfoiane, S-mathy IsuIfolane, dimeihy isuIfoxide, trlmethyiphosphate and methoxy-substiuted nitriles.
11. 14, A debtee oomprising an electrolyte foumuiafloh according to one or more of claims 6 to 13 which is a solar cell, an optioit detector, a photoreceptor, a photodiode, a photomultiplier, a photo resistor, a photo detector, a fightsensitive defector, a sohd-state inode, a transistor, an integrated circuit, a fieid-quench device, a ilg.ht^m%?h| device, a laser, a laser diode, a piasmon. emitting device, an elaotmplietopfaphy devise m a wave converter:.
12. 15. A device according to claim 14 which is a solar celt