Three-dimensional simulations of a thin film heterojunction solar cell with a point contact/defect passivation structure at the heterointerface

Thin film heterojunction solar cells such as those based on the chalcopyrites or amorphous silicon are often limited by interface recombination at the active heterointerface. A new strategy to overcome this limitation is described, replacing the conventional wider band gap contact material with a combination of a passivation layer plus the conventional contact in a point contact type structure. This is similar to the established method to minimize rear contact recombination in crystalline silicon solar cells. Here point contacts at the heterointerface of a $CuInS2$ based solar cell are modeled using the WIAS-TeSCA code. The importance of the donor defect energy level at the absorber/passivation interface is shown, and a way to improve the cell efficiency by $>25%$ (relative) is outlined.