Buried Solvent Assisted Perovskite Crystallization for Efficient and Stable Inverted Solar Cells

Abstract

Inverted (pin-type) organic-inorganic perovskite solar cells (PSCs) have very attractive for next generation photovoltaic cells, due to the advantages of low cost and facile fabrication. However, solution processed PSCs usually suffer from unsatisfactory power conversion efficiency (PCE), results from the defective perovskite layer and undesired interfacial property of PVK/PTAA. Here, pyridine (Py) is first used as a solvent for Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) and with low temperature annealing process. Due to the enhancement of polaron delocalization on the PTAA chains which affect by Py, it leads to obtain high uniformity PTAA film with low resistance. Meanwhile, buried Py induces the formation of high crystallinity perovskite film due to the presence of excess PbI 2 which result from corrosion of cationic salts by pyridine and ameliorated hydrophobic property of PTAA. Besides, PTAA (Py) based PVK film also exhibits lower defect densities and residual strain because of lewis-base Py can bind to uncoordinated Pb 2+ at perovskite surface. Finally, we achieve a champion PCE of 21.31% with PTAA (Py) based devices and the long-time/thermal/humidity stability of unencapsulated devices is significantly improved.

Keywords: PTAA, pyridine, crystallinity, perovskite solar cells, stability