Solution-processed CuI as hole transport layer for Sn-Pb perovskite solar cells

Abstract

Mixed tin-lead (Sn-Pb) perovskites have received a lot of attention as active layers for both single junction and tandem solar cells because of their optimal band gap. Generally, Sn-Pb perovskite solar cells are fabricated in the p-i-n structure using PEDOT:PSS as the hole transport layer (HTL), though its hygroscopic nature adversely affects the long-term stability of the perovskite layer.Here we propose copper iodide (CuI), with its high conductivity, wide bandgap, and optical transparency, as a low-cost and earth-abundant HTL candidate for Sn-Pb perovskite solar cells.Utilizing CuI as HTL and using an active layer composed of EACl 0.015 Cs 0.25 FA 0.75 Sn 0.5 Pb 0.5 I 3 passivated with sodium fluoride (NaF) we obtained a remarkable short circuit current of 32,85 mA/cm 2 for a champion power conversion efficiency of 20.1%, while control devices with PEDOT:PSS show an efficiency of 19.03% and a J sc of 30.59 mA/cm -2 . In addition, the implemented CuI layer improved the device stability when stored in N 2 and under thermal stress condition at 85 °C.