Na2S decorated NiOx as effective hole transport layer for inverted planar perovskite solar cells

NiOx have been considered as an excellent material for hole transport layer (HTL) of perovskite solar cells because of its wide band gap, excellent optical transmittance, proper chemical stability and energy level matching with perovskite materials. However, the power conversion efficiency (PCE) of inverted perovskite solar cells (PSCs) is hindered by the low conductivity of unmodified NiOx. Here, we reported an operative Na2S treated NiOx HTL, which could optimize the conductivity of the NiOx layers and the crystallinity of perovskite. The synergistic effect of Na cations and S anions could strengthen the conductivity of the NiOx HTL, improve the interface contact between NiOx and perovskite, and enhance the quality of the perovskite film, so as to boost photoelectricity performance of the device. The carrier dynamics have shown that doping of Na2S could not only diminish the interface defects of the HTL/perovskite layer, but also improve the hole extraction at the NiOx/perovskite interface. All these factors led to the improvements in short-circuit density (Jsc), fill factor (FF) and PCE of inverted planar perovskite solar cells. Consequently, Na2S-decorated NiOx HTL contributes to a stable device which attains a champion efficiency of 16.9%.