Solution-processed Sr-doped NiOx as hole transport layer for efficient and stable perovskite solar cells

Nickel oxide (NiO x ) hole transport layer (HTL)-based planar perovskite solar cells (PSCs) have attracted much attention due to high power conversion efficiency (PCE) and simple processing. In this work, smooth and compact Sr-doped NiO x films with different Sr doping concentration were successfully prepared through a simple low temperature sol-gel method. The 1 at.% Sr-doped NiO x HTL-based PSCs exhibited the best performance with PCE of 20.07%, which is greatly higher than PCE of reference NiO x based PSCs (15.73%). Furthermore, the unencapsulated PSCs based on Sr:NiO x HTL still retains over 60% of the original PCE value aging for 100 days under ambient air, showing better stability. The superior performance of Sr-doped NiO x based PSCs is attributed to better electrical conductivity, crystallinity of perovskite film and energy level matching with perovskite layer, which can greatly improve hole transport and extraction abilities and reduce carrier recombination, resulting in high PCE and better stability.