NiOx thin films prepared by liquid phase deposition (LPD) method for hole transport layers in inverted perovskite solar cells

Abstract

Nickel oxide (NiOx) thin films were prepared by liquid phase deposition (LPD) mehod and applied as hole transport layers (HTLs) in inverted perovskite solar cells (PSCs). The as-deposited α-3Ni(OH)2 · 2H2O films with porous nanoflake morphology were converted to NiOx by heat treatment at 500 °C. The heat-treatment duration was varied from 1 to 3 h to tune the chemical state and electrical properties of the LPD-NiOx films. X-ray photoelectron spectroscopy and Mott–Schottky analysis revealed that prolonged heat treatment increased the Ni3+/Ni2+ ratio and acceptor concentration. PSCs using the NiOx film heat-treated for 3 h exhibited the highest power conversion efficiency of 13.69%. Photoluminescence, external quantum efficiency, electrochemical impedance spectroscopy, and light-intensity-dependent measurements indicated that the improved performance originated from enhanced hole extraction and suppressed interfacial recombination. These results suggest that LPD-derived NiOx thin films have potential as solution-processed inorganic HTLs for inverted PSCs.