Effect of the post-annealing temperature on the thermal-decomposed NiO_x hole contact layer for perovskite solar cells

A hysteresis-less inverted perovskite solar cell (PSC) with power conversion efficiency (PCE) of 13.57% was successfully achieved based on the thermal-decomposed NiOx hole contact layer, possessing better electron blocking and hole extraction properties for its suitable work function and high-conduction band edge position. Herein, the transparent and high-crystalline NiO_x film is prepared by thermal-decomposing of the solution-derived Ni(OH)₂ film in our study, which is then employed as hole transport layer (HTL) of the organic-inorganic hybrid PSCs. Reasonably, the post-annealing treatment, especially for the annealing temperature, could greatly affect the Ni(OH)₂ decomposition process and the quality of decomposed NiO_x nanoparticles. The vital NiO_x HTLs with discrepant morphology, crystallinity and transmission certainly lead to a wide range of device performance. As a result, an annealing process of 400°C/2 h significantly promotes the photovoltaic properties of the NiOx layer and the further device performance.