V2Ox-based hole-selective contacts for c-Si interdigitated back-contacted solar cells

Abstract

Over the last few years, transition metal oxide layers have been proposed as selective contacts both for electrons and holes and successfully applied to silicon solar cells. However, better published results need the use of both a thin and high quality intrinsic amorphous Si layer and TCO (Transparent Conductive Oxide) films. In this work, we explore the use of vanadium suboxide (V₂O_x) capped with a thin Ni layer as a hole transport layer trying to avoid both the intrinsic amorphous silicon layer and the TCO contact layer. Obtained figures of merit for Ni/V₂O_x/c-Si(n) test samples are saturation current densities of 175 fA cm⁻² and specific contact resistance below 115 mΩ cm² on 40 nm thick V₂O_x layers. Finally, the Ni/V₂O_x stack is used with an interdigitated back-contacted c-Si(n) solar cell architecture fully fabricated at low temperatures. An open circuit voltage, a short circuit current and a fill factor of 656 mV, 40.7 mA cm⁻² and 74.0% are achieved, respectively, leading to a power conversion efficiency of 19.7%. These results confirm the high potential of Ni/V₂O_x stacks as hole-selective contacts on crystalline silicon photovoltaics.