Development and prospects of surface passivation schemes for high-efficiency c-Si solar cells

Photovoltaic (PV) electric power generation has the potential to account for a major portion of power generation in the global power market. Currently, the PV market is dominated by crystalline silicon (c-Si) solar cells which accounts for more than 80% of the share. Lower cost, optimized process parameters and improved PV cell efficiencies are required to reduce the overall cost per watt peak (W). In this regard, PV cell manufacturers are currently adopting thinner wafers, which tends to increase the surface recombination velocity (SRV). Excellent surface passivation at the front and rear of the PV cell becomes imperative for realizing superior efficienciy on c-Si substrates. In this article, our focus is to discuss the role of the surface passivation process for improving the PV cell efficiency. The fundamentals and strategies to improve the surface passivation for c-Si solar cells are discussed. Surface passivation schemes and materials with the ability to offer field effect passivation with dielectric charges (positive/negative) present in the passivation films were reviewed. Moreover, we discuss the use of a thin-dielectric passivation layer with a properly selected work function and band offsets for tunneling contacts, facilitating a higher efficiency potential. Finaly, the front/rear surface passivation schemes required for thinner wafers to maintain higher bulk lifetime and higher efficiencies for c-Si solar cells are presented.