Solution-processed vanadium oxide by low-temperature annealing for silicon solar cells with hole selective contact

Transition metal oxides (TMOs) with high work function (V2O5, MoO3, WO3) are very promising hole selective materials for high-efficiency crystalline silicon solar cells, as they can provide excellent hole transport and electron blocking capabilities simultaneously. However, the TMOs are typically obtained using vacuum deposition techniques (thermal evaporation, atomic layer deposition or sputtering), for which the preparation process is complex and the requirement for the equipments is relatively high. In this work, we prepared vanadium oxide (V2O5-X) films using low-cost solution method as the hole-selective transport layer for silicon heterojunction solar cells. The low temperature post-annealing treatment at 150 °C reduces the surface roughness of film and improves the passivation contact performance with p-Si. Furthermore, annealing in an oxygen-deficient atmosphere (N2/H2 = 95/5) improves the carrier transport due to increased oxygen vacancies and enhances the surface passivation ascribed to the additional role of hydrogen. Combined with the annealing treatments and optimized device processes, the V2O5-X/p-Si heterojunction solar cells have achieved a conversion efficiency of 17.23%, which is the highest reported so far based on solution-processed V2O5-X for crystalline silicon solar cells.