Conjugated molecule doping of triphenylamine-based hole-transport layer for high-performance perovskite solar cells

High performance perovskite solar cells (PSCs) with p-i-n device architecture often employ poly[bis(4-phenyl) (2,4,6-trimethylphenyl)amine (PTAA) as the hole-transporting layer. However, PTAA has a low intrinsic carrier concentration and generally requires dopants to enhance the conductivity, but most dopants will induce deleterious effects especially on the stability and hysteresis behavior of the devices. Here, we synthesize a novel conjugated carbazole-based molecule (TCzP) as dopant of PTAA to improve the conductivity and stability simultaneously for high-performance PSCs. Specifically, TCzP contributes to the reduction of energy barrier between PTAA and perovskite and to the formation of high-quality perovskite films owing to its intrinsic hydrophilicity for better association with the polar perovskite precursor. Therefore, PSCs by TCzP-doping exhibit significantly improved power conversion efficiency up to 18.3% in comparison to 16.0% of the device using dopant-free PTAA. Moreover, TCzP-doped PTAA leads to lower hysteresis and much better long-term stability up to 500 h of the PSCs in air. We believe this work would pave a new way towards high-performance inverted PSCs by exploring conjugated molecules as PTAA dopants to develop highly efficient and stable organic hole-transporting layers.