Nanowire solar cells using hydrogenated amorphous silicon: A modeling study

Abstract

AbstractAn interesting example of device combining amorphous material and nano‐ or microstructure is the wire solar cell. Solar cells based on silicon nano‐ or microwires have attracted much attention as a promising path for low cost photovoltaic technology. The key point of this structure is the decoupling of the light absorption from the carriers collection. In this work, we use numerical modeling to study two types of radial junction structures: (i) a p–n heterojunction for which p‐or n‐type crystalline silicon (c‐Si) wires are covered by a conformal n‐ or p‐ doped amorphous silicon (a‐Si:H) thin layer and (ii) thin film a‐Si:H p–i–n radial structures realized by conformal covering on thinner c‐Si wires. In the first structure, the a‐Si:H layer is only intended to form the heterojunction and light absorption takes place in the c‐Si wires, whereas in the second one, the absorber material is the a‐Si:H i‐layer and its thickness can be optimized to facilitate the carrier separation and collection. The potential of those both types of Si wires based solar cells will be compared according to the structure design and material properties. Furthermore, the sensitivity of the a‐Si:H p–i–n radial cells to the light‐soaking effect, i.e., the increase of deep defect density resulting from the breaking of weak silicon bonds, will be studied and compared to what is commonly observed on classical a‐Si:H planar p–i–n cells.