Hot hole transport in a-Si/c-Si heterojunction solar cells

The transport behavior of photogenerated minority carriers in an a-Si/c-Si heterojunction solar cell is dependent on the energy distribution function (EDF) of the carriers impinging on the hetero-interface. The high field region at the interface results in a strongly non-Maxwellian distribution of holes incident on the surface, which has implications for current collection and a significant impact on the overall efficiency of the device. This work studies the effect of the high field transport on photogenerated carriers at the hetero-interface through a combination of Monte Carlo simulations and analysis of defect assisted transport. A three band warped non-parabolic band model is implemented to describe the valence band in order to accurately represent high energy photocarriers. Also, percolation path theory is applied to study defect assisted transport in the intrinsic amorphous region by considering mechanisms such as defect capture through tunneling, emission through Poole - Frenkel effect, and emission through tunneling.