Advanced silicon thin films for high-efficiency silicon heterojunction-based solar cells

The drop in passivation usually observed after the deposition of the p-doped amorphous silicon (a-Si:H) layer on top of the passivating intrinsic buffer a-Si:H layer during the fabrication of silicon heterojunction (SHJ) solar cells is shown to be mostly related to the properties of the i-layer itself. After optimization of the i-layer to reduce this loss, minority carrier lifetimes above 50 ms were achieved on very lowly doped wafers, and close to 18 ms on actual SHJ cell precursors with i-layers as thin as 4 nm. These films were integrated into SHJ solar cells fabricated with industry-compatible processes, yielding efficiencies up to 23.1% on large-area devices and up to 23.9% on 4 cm² devices. In addition, the developed a-Si:H layers were also used as key building blocks in more advanced high-efficiency solar cell architectures, such as interdigitated back-contacted SHJ solar cells (>23%), III-V//SHJ tandems (>30%), and perovskite//SHJ tandems (>25%), for example.