Doped Nickel Oxide Carrier-Selective Contact for Silicon Solar Cells

Transition metal oxides such as MoO3, WO3, V2O5, and NiO have shown potential as hole-selective passivating contact for crystalline silicon (c-Si) solar cells. Among them, NiO is a notoriously poor hole-conducting semiconductor. Doping metal oxide with multivalent metal cations is an effective method to modify their electronic properties because dopant-induced favorable defect states play a crucial role in charge carrier transport in device applications. We use first-principles density functional theory to identify suitable metal cations that favorably affect the hole-conducting properties of NiO. We identify Al, Mg, and Zn as suitable dopants for NiO, improving ohmic contact properties with c-Si. Subsequently, Al-doped NiO (AlxNiyO) films were synthesized onto c-Si using an atomic layer deposition supercycle approach. The AlxNiyO films showed a contact resistivity of 331 mΩ cm2 with c-Si, in contrast to undoped NiO where no ohmic contact could be formed. This in-depth computational study followed by the experimental synthesis of AlxNiyO films removes a critical barrier for the future applications of NiO-based carrier-selective passivating contacts for c-Si and other types of solar cells and provides a path for the optimization of other functional materials.