Heterojunction Doping of Poly(triarylamine) with Cesium-Doped Vanadium Oxide via Interfacial Electron Transfer toward High-Performance Perovskite Solar Cells

As an alternative to the traditional blend casting method, a novel heterojunction doping approach is developed to dope hole extraction layers (HELs) for greatly boosting the efficiency of charge carrier collection in perovskite solar cells (PSCs). The HELs are prepared by sequential deposition of Cs-doped VO_x and poly­(triarylamine) (PTAA) thin films, and extensive heterojunction doping is observed in the contact interface between the two thin films due to the presence of electron transfer from PTAA to Cs-doped VO_x. The interfacial doping in the Cs-doped VO_x/PTAA HELs enhances their conductivity and improves their energy level alignment. These increase V_OC, J_SC, FF, and power conversion efficiency (PCE) in PSCs compared to those in the PSCs with the use of Cs-doped VO_x and PTAA separately.