Accurate evaluation of minority carrier diffusion length in thin film single crystalline silicon solar cells

Thin film single crystalline silicon solar cells were fabricated and minority carrier diffusion length was evaluated using two-dimensional simulation. Effective minority carrier diffusion length (L_eff) in 19 μm-thickness cell was obtained as 19 μm by the surface photovoltage (SPV) method. Further, bulk minority carrier diffusion length (L_b) was estimated to over 50 μm from fitting for external quantum efficiency (EQE) using numerical simulation. In the case of L_b ≥ cell thickness, L_eff estimated from SPV was limited to the thickness of the cell, and L_b could not be evaluated accurately. Therefore, fitting of EQE in the wide wavelength region by two-dimensional simulator was indispensable for accurate evaluation of minority carrier diffusion length in thin film single crystalline silicon solar cells.