NiCo2O4 thin film prepared by electrochemical deposition as a hole-transport layer for efficient inverted perovskite solar cells

Abstract

Spinel NiCo₂O₄ is a promising p-type semiconductor for optoelectronic devices; however, it is difficult to prepare uniform and large-area NiCo₂O₄ films, which hinders its application as a hole transport material for perovskite solar cells (PSCs). In this study, a novel, mild, and low-cost KCl-assisted electrochemical deposition (ECD) approach was developed to directly prepare a uniform NiCo₂O₄ film on a fluorine-doped tin oxide (FTO) substrate. A uniform NiCo₂O₄ film prepared through an ECD approach was used as a hole-transport layer (HTL) in inverted PSCs. The resulting NiCo₂O₄ HTL-based device achieved a power conversion efficiency (PCE) of 19.24% with negligible hysteresis and excellent reproducibility. Additionally, it outperformed a NiO_x-based device (PCE = 18.68%). The unsealed devices retained 90.7% of their initial efficiency when subjected to stability measurements for 360 h in an ambient atmosphere. This study shows the great potential of ECD-prepared NiCo₂O₄ HTLs for large-area PSCs in the future.