Optimization of halide perovskite solar cells based on nanocolumnar ZnO

•The ZnO(AZO)/CH3NH3PbI2 interface has been investigated by ab initio density functional calculations.•The partial density of states analysis indicates a spike in the band diagram at the ZnO/CH3NH3PbI3 interface.•An ideal band alignment is recovered by introducing an interfacial AZO layer.•Tuning the band offset by Al-doping is consistent with the observed enhanced PCE.

Halide perovskite solar cells based on nanocolumnar ZnO are considered alternative candidates to the more established TiO2 based devices. Replacing the scaffold oxide layer by ZnO has the benefit of a larger electron mobility and lower processing temperatures, still reaching power conversion efficiencies (PCEs) of over 15%. The perovskite layer stability and improving the PCE are currently two major issues under investigation. Regarding the latter, the presence of an interfacial layer of Al-doped ZnO (AZO) gives an enhanced power output, as it was recently reported. Using density functional theory calculations we discuss the band alignment at the ZnO (AZO) - halide perovskite interface, indicating one possible source for the enhanced PCE.