AgAl alloy electrode for efficient perovskite solar cells

We report efficient mixed halide perovskite solar cells using thermally evaporated Ag or AgAl alloy layers as back electrodes. The properties of AgAl alloy and Ag films deposited on a hole-transport material layer for use in CH₃NH₃PbI_3-xCl_x solar cells were investigated. The influence of the distance between the metal source and the sample on the performance of the solar cells was determined. The cell with an Ag layer deposited at a distance of 20 cm displayed a power conversion efficiency (PCE) of 5.49%. When the Ag layer was deposited at a distance of 30 cm, the resulting device achieved a 46.8% enhancement in PCE compared to the cell with the Ag prepared at 20 cm. Furthermore, the AgAl alloy based perovskite solar cell accomplished a 37.3% enhancement in PCE compared to the optimized Ag electrode. The fabricated AgAl alloy perovskite cells show a fill factor of 59.6%, open-circuit voltage of 0.88 V, short-circuit current density of 21.11 mA cm^-2, yielding an overall efficiency of 11.07%. The AgAl alloy layer exhibited high optical reflectivity and good adhesion on the hole-transport material layer compared to a layer of Ag. The PCE enhancement mechanisms are discussed. Our work has demonstrated that AgAl is a promising back electrode material for high-efficiency perovskite solar cells.