Enhanced Charge Transport in Inverted Perovskite Solar Cells via Electrodeposited La-Modified NiO x Layers

This work explored an electrochemical approach for synthesizing lanthanum-modified nickel oxide (NiO x :La) as a hole transport layer (HTL) in inverted perovskite solar cells (IPSCs). By varying the La 3+ concentration, the chemical, charge transport, structural, and morphological properties of the NiO x :La film and the HTL/PVK interface were evaluated to enhance photovoltaic performance. X-ray photoelectron spectroscopy (XPS) confirmed La 3+ incorporation, a higher Ni 3+ /Ni 3+ ratio, and a valence band shift, improving p-type conductivity. Electrochemical impedance spectroscopy and Mott–Schottky analyses indicated that NiO x :La 0.5% exhibited the lowest resistance and the highest carrier density, correlating with higher recombination resistance. The NiO x :La 0.5% based cell achieved a PCE of 20.08%. XRD and SEM confirmed no significant changes in PVK structure, while photoluminescence extinction demonstrated improved charge extraction. After 50 days, this cell retained 80% of its initial PCE, whereas a pristine NiO x device retained 75%. Hyperspectral imaging revealed lower optical absorption loss and better homogeneity. These results highlight NiO x :La as a promising HTL for efficient and stable IPSCs.