High-efficiency hydrogenated amorphous/crystalline Si heterojunction solar cells

The heterojunction crystalline silicon (c-Si) solar cell is one of the most promising cell structures for high-performance and low-cost solar electricity generation. Efficiencies of more than 22% and the highest open-circuit voltage (0.739 V) for c-Si solar cells have been achieved by the Sanyo group with this structure. A thin intrinsic layer of hydrogenated amorphous silicon combined with doped layers effectively passivates the c-Si surface, reducing surface defects, but also allows carriers to pass through the passivating layer without significant loss. It is this feature that makes a-Si:H uniquely different than other dielectric passivation layers, such as silicon dioxide or silicon nitride. The heterojunction structure uses wider bandgap materials to contact c-Si, preventing carriers from moving onto the wrong side of the junction and then recombining. In this paper, we will review c-Si solar cells with hydrogenated amorphous silicon emitters and back contacts.