The silicon hetero-junction (SHJ) technology holds the current efficiency record of 25.6% for silicon-based single junction solar cells and shows great potential to become a future industrial standard for high-efficiency crystalline silicon (c-Si) cells. One of the main advantages of this concept over other wafer based silicon technologies are the very high open-circuit voltages that can be achieved thanks to the passivation of contacts by thin films of hydrogenated amorphous silicon (a-Si:H). The a-Si:H/c-Si interface, while central to the technology, is still not fully understood in terms of transport and recombination across this nanoscale region, especially concerning the role of the different localized tail and defect states in the a-Si:H and at the a-Si:H/c-Si interface and of the band offsets and band bending induced by the heterostructure potential and the large doping, respectively. For instance, a consistent microscopic picture of transport and recombination processes with treatment of thermal and tunneling mechanisms on equal footing is lacking. On the other hand, there are new SHJ device architectures like thin wafers with light trapping structures [1] or interdigitated back contact (IBC) cells [2], which define additional requirements for the modelling approach concerning the integration of 3D optical and electrical simulations. This paper provides an overview over our current efforts in the creation of a multi-scale and multi-physics framework to deal with the challenges encountered in the simulation of SHJ solar cells.
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