Exploring Non-Stoichiometric Nickel Oxide (NiOx) as a Hole Transport Layer for Cesium Tin Triiodide (CsSnI3) Perovskite Solar Cells

Abstract

Inverted planar CsSnI3 perovskite p-i-n structure shows a high potential as a candidate for inorganic lead-free perovskite solar cells (PVSCs). Nickel oxide (NiOx) offers promising characteristics for a winning hole transport layer (HTL), such as high optical transmittance, high stability, easy processability, and a wide band gap that allows high hole mobility and good electron blocking ability. In this work, NiOx was synthesized by first forming Ni(OH)2 in the precipitation reaction of (Ni(NO3)2· 6H2O) and NaOH. The synthesized NiOx nanocrystals was dissolved in DI water to different concentrations and used as a HTL in the inverted p-i-n CsSnI3 PVSCs. The effects of annealing condition, concentration of NiOx ink and spin speed on the NiOx film morphology and surface roughness were explored. In addition, CsSnI3 thin films were fabricated to be the active layer and solar cells with the inverted structure were fabricated and tested.