Impurity photovoltaic effect in indium-doped silicon solar cells

Impurity photovoltaic effect is investigated in two groups of indium-doped single-crystalline silicon solar cells with n-type and p-type dopants in the base layer. The continuity equation for minority carriers is solved numerically using the charge neutrality condition and current-voltage characteristics are found. It is shown that the improvement of short-circuit current due to carrier photogeneration from the deep defect level is negligible for both groups of the cells considered. Short-circuit current increases with increasing the trap concentration and open-circuit voltage abruptly decreases for trap concentrations close to compensation by n-type dopant. However, these dependencies occur due to the increase of lifetime, the decrease of the total equilibrium carrier density, and take place even in the absence of the absorption of subgap photons. It is shown that indium is not the proper impurity for efficiency improvements of silicon solar cells due to the impurity photovoltaic effect.