A-site cation engineering enables oriented Ruddlesden-Popper perovskites towards efficient solar cells

Quasi two-dimensional(Q-2D) perovskites with favorable environment stability and satisfied device performance are attracting great attention and becoming star materials.The unique characteristics of more wide range of Goldschmidt tolerance factor endow Q-2D perovskites with exceptional composition tunability and great potential.Herein,Guanidinium(Gua) was firstly introduced into the octahedral cation site of BA2MA3Pb4I13perovskite to partially replace methylammonium(MA).With the incorporation of Gua,the XRD intensity ratio of(202)/(111) increased nearly 100% for control and 0.10Gua-mixed Q-2D perovskite,from1.49 to 2.84,indicating that the layered perovskite crystallization orientation is significantly regulated.Coupling with GIWAXS results,a preferential orientation Q-2D perovskite film was obtained.Meanwhile,the Gua-based Q-2D perovskite exhibits significantly reduced nonradiative recombination,which greatly promotes the efficient transport of carriers leading to a high efficiency of 15.41% in the BA2(MA0.9GA0.1)3Pb4I13-based solar cell.Moreover,the solar cells display superior environmental stability at an average humidity of 35%±5% in the air for 1200 h.This work points the way to the regulation of crystal orientation for enhancing the performance of Q-2D perovskite by the A-site cation engineering.