Interaction at the silicon/transition metal oxide heterojunction interface and its effect on the photovoltaic performance†
Abstract
The interfacial reaction and energy level alignment at the Si/transition metal oxide (TMO, including MoO3−x, V2O5−x, WO3−x) heterojunction are systematically investigated. We confirm that the interfacial reaction appears during the thermal deposition of TMO, with the reaction extent increasing from MoO3−x, to V2O5−x, and to WO3−x. The reaction causes the surface oxidation of silicon for faster electron/hole recombination, and the reduction of TMO for effective hole collection. The photovoltaic performance of the Si/TMO heterojunction devices is affected by the interface reaction. MoO3−x are the best hole selecting materials that induce least surface oxidation but strongest reduction. Compared with H-passivation, methyl group passivation is an effective way to reduce the interface reaction and improve the interfacial energy level alignment for better electron and hole collection.