Novel Boron-Doped p-Type Cu₂O Thin Films as a Hole-Selective Contact in c-Si Solar Cells

p-type Cu₂O thin films doped with trivalent cation boron are demonstrated for the first time as an efficient hole-selective layer for c-Si heterojunction solar cells. Cu₂O and Cu₂O:B films were deposited by rf magnetron sputtering, and the optical and electrical properties of the doped and undoped films were investigated. Boron doping enhanced the carrier concentration and the electrical conductivity of the Cu₂O film. The band alignment of the Cu₂O:B/Si heterojunction was investigated using XPS and UPS measurements. The Cu₂O:B/Si interface has a valance band offset of 0.08 eV, which facilitates hole transport, and a conduction band offset of 1.35 eV, which blocks the electrons. A thin SiO tunnel oxide interlayer was also explored as the passivation layer. The initial trials of incorporating this Cu₂O:B layer as a hole transporting layer in a single heterojunction solar cell with the structure, ITO/Cu₂O:B/n-Si/Ag, and a cell area of 1 cm² yielded an open-circuit voltage of 370 mV, a short-circuit current density of 36.5 mA/cm², and an efficiency of 5.4%. This p-type material could find potential applications in various optoelectronic applications like organic solar cells, TFTs, and LEDs.