NiCo(2)O(4) thin film prepared by electrochemical deposition as a hole-transport layer for efficient inverted perovskite solar cells

Spinel NiCo(2)O(4) is a promising p-type semiconductor for optoelectronic devices; however, it is difficult to prepare uniform and large-area NiCo(2)O(4) 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 NiCo(2)O(4) film on a fluorine-doped tin oxide (FTO) substrate. A uniform NiCo(2)O(4) film prepared through an ECD approach was used as a hole-transport layer (HTL) in inverted PSCs. The resulting NiCo(2)O(4) 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 NiCo(2)O(4) HTLs for large-area PSCs in the future.