Optimal optical generation profiles in a-Si:H p–i–n solar cells

The dependence of the maximum power output PM and short-circuit current JSC on the form (relative variation with position) of the optical generation rate profile in an a-Si:H p–i–n solar cell has been investigated computationally. It was found that there was an optimal form for the generation profile, and that PM increased from 4.64 to 5.29 mW cm−2, an increase of about 14%, when this optimal generation profile was used in the simulation. Optimal doping of the i-layer of the cell with phosphorous led to a PM of 5.60 mW cm−2, and when the optimal generation profile for this P-profiled cell was found, it yielded a PM of 7.86 mW cm−2, an increase of about 40%. This suggests that the combination of P-profiling and optimal generation could lead to significant improvements in cell performance. Moreover, it was found that for both cells the form of the optimal generation profile could be associated with the position of the peak in the external quantum efficiency, obtained from the spectral response. The possibility of using band-gap grading to achieve an optimal generation rate profile has been suggested.