Transport Losses at the TCO/a-Si:H/c-Si Heterojunction: Influence of Different Layers and Annealing
To improve silicon heterojunction solar cells even further, minimizing transport losses within the charge carrier selective junctions and layers is mandatory. With this in mind, we present a systematic quantification of the transport losses of the electron (contact resistivity, rc ≈ 30 mO·cm²) and hole ( rc ≈ 240 mO·cm²) contact of our silicon heterojunctions, which enable fill factors above 80% on cell level. We identify the cause of the higher transport losses of the hole contact to be the intrinsic a-Si:H and ITO layer and that these layers are also responsible for a limited thermal stability. Furthermore, temperature-dependent I-V measurements reveal the nonohmic nature of the transport losses in case that intrinsic a-Si:H and transparent conductive oxide are part of the heterojunction.