MoO₃ doped PTAA for high-performance inverted perovskite solar cells

The hole transport layer (HTL) plays a key role in determining the performance of planar perovskite solar cells (PSCs). Poly[bis(4-phenyl)(2,4, 6-triMethylphenyl)aMine] (PTAA), a polymer with good stability, is one of the promising HTL candidates for PSCs. However, notable interfacial carrier recombination limits the performance of PSCs based on PTAA HTL, due to the large gap between the highest-occupied molecular orbital (HOMO) of PTAA and the valance band maximum (VBM) of MAPbI₃ perovskite as well as the low intrinsic hole mobility of PTAA. Herein, PTAA was doped by 3 wt% of molybdenum oxide (MoO₃) to move down its HOMO by 0.16 eV, leading to a better matching with the MAPbI₃ perovskite. Meanwhile, the MoO₃ dopant was demonstrated to improve the hole transport in PTAA and hole extraction at the PTAA/perovskite interface. Eventually, the fabricated inverted planar PSCs using PTAA HTL with 3 wt% MoO₃ achieved the PCE of 20.06% as compared to that of 17.71% by using pristine PTAA HTL. The present work thus proposes a simple approach to utilize MoO₃ as a dopant to substantially improve the molecular HTLs for high-performance PSCs and other perovskite-based optoelectronics.