The investigation of CsPb(I_1−xBr_x)₃/crystalline silicon two- and four-terminal tandem solar cells

It is well known that the phase stability of CsPb(I_1−xBr_x)₃ (0 ≤ x ≤ 1) perovskite materials is enhanced under humid environments with the increase of Br⁻ concentration in film, however, the bandgap (E_g) is also widened synchronously, resulted in limiting the light harvesting and then reducing the power conversion efficiency (PCE) of devices. Hence, how to realize the compatibility of high stability and high PCE is a challenge for device based on CsPb(I_1−xBr_x)₃. In this work, the two- (2-T) and four-terminal (4-T) tandem solar cells (TSCs) consisting of a CsPb(I_1−xBr_x)₃ top sub-cell and a crystalline silicon (c-Si) bottom sub-cell are constructed and compared. It is found that in the case of 2-T configuration, performance of device is very sensitive to the E_g and the thickness of top sub-cell, and a maximum PCE of 29.23% is achieved only for the CsPbI₃ top sub-cell at an optimum thickness of 275 nm. However, in the 4-T formation, devices present a weak dependence on the E_g and the thickness of top sub-cell, and PCEs above 28.5% can be obtained when CsPbBr₃ is used as top sub-cell. These results highly underline the application potential of 4-T CsPb(I_1−xBr_x)₃/Si TSCs, especially for CsPbBr₃/Si TSC.