Monolithic perovskite/Si tandem solar cells exceeding 22% efficiency via optimizing top cell absorber

Among all tandem photovoltaic (PV) techniques, the perovskite/Si tandem is of particular interest as it capitalizes the mature silicon industry with decades of experience. Photo-current matching between two sub-cells is a prerequisite to achieve high efficiency in monolithic tandem cells. Here we report a low-temperature solution process for efficient perovskite/Si tandem solar cell. A highly-efficient perovskite/Si monolithic tandem cell is constructed by adjusting the electrical and optical properties of electron transport layer, and optimizing the bandgap and the optical density of perovskite absorber. With the optimized condition, the tandem cell with 1.69 eV bandgap of the perovskite absorber delivers a power conversion efficiency (PCE) of 22.22%. The steady state efficiency output at 1.42 V could reach over 20.6% over 200 s illumination. In addition, the stability of perovskite/Si two-terminal tandem devices is promising, which retains more than 85% of its original efficiency after 500 h stability test.