Application Of Hole-Transport Material Based On Indolocarbazole And Small-Molecule Dopant In Solid-State DSSCs

Dye sensitized solar cell（DSCs）attracts wide attention because of its low-cost,simple procedures and high efficiency.However due to its liquid electrolyte suffers from potential leakages problems associated with the corrosive and volatile nature,it’s possible that solid-state dye sensitized solar cells make the large-scale applications practical.Hole-transport material（HTM）reducts the dye of oxidation state in solid-state DSCs（ssDSSCs）.To date,the focus of most solid-state DSCs is based on the2,2’7,7’-tetrakis（N,N-dimethoxyphenylamine）-9,9’-spriobifluorene（Spiro-OMeTAD）which has the best efficiency up to now.However,its high cost,fairly low conductivity and the cation of Spiro-OMeTAD has absorption in visible region which can compete with the sensitizers to absorb light have made alternatives desirable.Chemical doping in HTM spin-coating solution is an efficient way to enhance the mobility in HTMs which will improve the overall power conversion efficiency of solar cells.In the first part,hole-transport material based on indolocarbazole ZYY1 and ZYY2 have been synthesized and applied into ssDSSCs.And then ultraviolet absorption spectrum,electrochemical cycle voltammetry and photovaltaic performance have been tested and analyzed.However,ZYY1 and ZYY2 as hole-transport material show bad solubility in spin-soulution chlorobenzene,which influences electrons infiltrate into TiO₂ and the overall power conversion（0.15%,0.27%）.In order to improve the solubility of HTM,the spin-solution changes into the mixture of chlorobenzene and chloroform（v:v=1:1）,and the currentdensityincreasesfrom0.45mA/cm²to0.80mA/cm².2,3-Dichloro-5,6-dicyano-1,4-benzoquinone（DDQ）shows strong electrophilic quality because of its chemical structure.So in the second part of this paper,the effect of DDQ as p-type dopant in solid-state DSCS has been discussed.X1⁺-DDQ^-electron-transfer complex can be formed by doping DDQ into spin-coating solution with X1 as hole-transport material,and then compare the changes of conductivity and photovoltaic performance.It is shown that after doping DDQ,the series resistance of solid-state DSCs is significantly reduced,so the short-circuit current density has been improved.When doping 0.08%DDQ into spin solution with X1 as hole-transport material,the overall power conversion efficiency is 4.3%(J_sc=7.39m A/cm²,V_oc=0.80 V,ff=73%),while that of pristine solar cells is only 2.9%(J_sc=5.37m A/cm²,V_oc=0.84V,ff=65%).Because DDQ has been the successful p-type dopant into X1spin-solution,in this part DDQ has been also used in spin-solution with ZYY2 as HTM,the current density and fill factor have been improved,the overall power conversion efficiency increases from 0.14%to 0.29%.