单分子液晶添加剂在甲脒铅碘钙钛矿太阳能电池中的应用

Application of Single-molecule Liquid Crystal Additives in CH(NH2)2PbI3 Perovskite Solar Cells

溶液制备的钙钛矿薄膜通常含有大量晶界,会降低薄膜结晶质量,导致缺陷复合,不利于提升器件性能。因此,制备更高结晶质量的薄膜来进一步提升能量转化效率是钙钛矿太阳能电池面临的挑战。液晶分子具有强的自组装能力和形貌调节能力,本研究引入一种向列型单分子液晶4-氰基-4′-戊基联苯(5CB)作为甲脒铅碘(CH(NH2)2PbI3,FAPbI3)钙钛矿前驱液的添加剂,可以增大钙钛矿晶粒尺寸,减少晶界。此外,5CB的氰基能钝化钙钛矿晶粒表面未配位的Pb^(2+),降低缺陷态密度,从而抑制非辐射复合。经过优化,添加0.2 mg/mL 5CB的钙钛矿太阳能电池的能量转化效率达到21.27%,开路电压为1.086 V,电流密度为24.17 mA/cm^(2),填充因子为80.96%。本研究证明使用单分子液晶作为添加剂是提升FAPbI3钙钛矿电池性能的有效策略。

Solution-processed perovskite films usually contain a large quantity of grain boundaries,which decrease the film crystalline quality and introduce severe defect recombination,hindering performance of the devices based on them.Therefore,preparation of high-quality films to achieve high power conversion efficiencies remains a great challenge for perovskite solar cells.Due to high abilities of self-assembly and morphology-tuning for liquid crystal molecules,a single-molecule liquid crystal 4-cyano-4′-pentyl biphenyl(5CB)was employed as additive in CH(NH2)2PbI3(FAPbI3)precursor solution to increase the perovskite grain size and decrease the grain boundaries.In addition,the cyano group in 5CB passivates the uncoordinated Pb^(2+)in the perovskite films,which reduces the trap density concentration and inhibits the nonradiative recombination.The resulting perovskite solar cells with 0.2 mg/mL 5CB in the precursor achieve an efficient power conversion efficiency of 21.27%with an open circuit voltage of 1.086 V,a current density of 24.17 mA/cm^(2),and a fill factor of 80.96%.In conclusion,introducing single-molecule liquid crystal as additive is a facile and efficient strategy for improving the performance of FAPbI3 solar cells.