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

Abstract

Solution-processed perovskite films usually contain a large quantity of grain boundaries, which decrease the film crystalline quality and introduce severe defect recombination, hindering the device performance. Therefore, obtaining high-quality films and 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, this study employed a singlemolecule liquid crystal 4-cyano-4'-pentyl biphenyl (5CB) 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 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%, respectively. In conclusion, single-molecule liquid crystal additive is a facile and efficient strategy for improving the performance of FAPbI3 solar cells.