Silicon heterojunction solar cells: Techno-economic assessment and opportunities

The ever-increasing electricity demand from renewables has stimulated growth in the photovoltaic (PV) industry. Yet, while grid parity has already been achieved in several countries, a continued decline in module prices coupled with further efficiency improvements at an annual growth rate of ∼0.5%_abs are needed to sustain its market growth. Mainstream PV technologies are still based on crystalline silicon (c-Si) wafers with heavily doped regions and directly metallized contacts. However, these cause band-gap narrowing, Auger recombination losses, and contact recombination losses. Passivating contact (PC) technologies can overcome these limitations by decoupling surface passivation and contact formation requirements. Among PC technologies, amorphous silicon-based silicon heterojunction (SHJ) solar cells have established the world record power conversion efficiency for single-junction c-Si PV. Due to their excellent performance and simple design, they are also the preferred bottom cell technology for perovskite/silicon tandems. Nevertheless, SHJ technology accounts for only ∼2% of the current PV market share. In this review, we discuss the techno-economic challenges for large-volume SHJ manufacturing. In doing so, we highlight critical areas that need to be addressed for enabling terawatt-scale SHJ deployment.