Effects of structure and electronic properties of D-π-A organic dyes on photovoltaic performance of dye-sensitized solar cells

Herein,we examine the performance of dye-sensitized solar cells containing five D-π-A organic dyes designed by systematic modification of π-bridge size and geometric structure.Each dye has a simple push-pull structure with a triarylamino group as an electron donor,bithiophene-4,4-dimethyl-4 H-cyclopenta 1,2-b:5,4-b’]dithiophene(M11),4,4-dimethyl-4 H-cyclopenta[1,2-b:5,4-b’]dithiophenethiophene(M12),thiophene-4,4-dimethyl-4 H-cyclopenta[1,2-b:5,4-b’]dithiophene(M13),4,4-dimethyl-4 H-cyclopenta[1,2-b:5,4-b’]dithiophene-benzene(M14),and 4,4-dimethyl-4 H-cyclopenta[1,2-b:5,4-b’]dithiophene(M15)units asπ-bridges,and cyanoacrylic acid as an electron acceptor/anchor.The extension of theπ-bridge linkage favors wide-range absorption but,because of the concomitant molecular volume increase,hinders the efficient adsorption of dyes on the TiO_(2) film surface.Hence,higher loadings are achieved for smaller dye molecules,resulting in(i)a shift of the TiO_(2) conduction band edge to more negative values,(ii)a greater photocurrent,and(iii)suppressed charge recombination between the photoanode and the redox couple in the electrolyte.Consequently,under one-sun equivalent illumination(AM 1.5 G,100 mW/cm^(2)),the highest photovoltage,photocurrent,and conversion efficiency(η=7.19%)are observed for M15,which has the smallest molecular volume among M series dyes.

无机材料对高效钙钛矿太阳能电池缺陷的钝化

用有机材料进行表面钝化是提高钙钛矿太阳电池稳定性和效率的有效策略之一.但是,有机分子和钙钛矿层之间不牢固的键合作用仍不足以钝化各种缺陷以保护钙钛矿层免受氧气和水的侵蚀.最近,由于无机材料更稳定的化学键和更有效的钝化效果而逐渐成为研究的热门.含铅物质、碱金属卤化物、过渡元素卤化物、氧化物、疏水性物质等材料已被应用于钙钛矿太阳能电池表界面缺陷的钝化.这些无机材料通过控制钙钛矿的成核结晶过程以及形成物理保护层显著提高了器件的稳定性和效率.