We present and discuss advances in the development of p-type Si heterojunction solar cells with Al-doped ZnO (AZO) on both front and rear side, by means of mixed-phase Si- and SiOx-based doped layers. We demonstrate that while rear AZO can be deleterious when using p-type amorphous silicon (a-Si:H), p-type microcrystalline silicon (μc-Si:H) allows for: (1) suppression of the p-layer/AZO Schottky-like barrier, (2) relevant Voc increase, and (3) improved transport and extraction of carriers.
In contrast, Voc reduction and increased low-injection recombination is observed with n-type μc-Si:H in conjunction with AZO, likely due to the low defect density of the material which entails severe depletion effects. These issues are avoided with the more defective mixed-phase n-SiOx, which additionally provides for reduced parasitic absorption losses and is thus established as the optimal emitter choice.
Mercaldo, L.V., Bobeico, E., Usatii, I., Della Noce, M., Lancellotti, L., Serenelli, L., Izzi, M., Tucci, M. and Veneri, P.D., 2017. Potentials of mixed-phase doped layers in p-type Si heterojunction solar cells with ZnO: Al. Solar Energy Materials and Solar Cells, 169, pp.113-121.
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