Integrated and Unassisted Solar Water‐Splitting System by Monolithic Perovskite/Silicon Tandem Solar Cell

Photoelectrochemical (PEC) water splitting to hydrogen is a clean process that can achieve green hydrogen. However, the integrated PEC devices have some problems, such as serious incident light loss, poor stability, and high cost. Here, the low‐cost perovskite/silicon tandem cell instead of the costly III−V tandem cell as the light absorber is used, combined with high‐transmittance quartz glass as a protective layer forming an unassisted solar water‐splitting device. Quartz glass can minimize incident light loss and prevent electrolyte corrosion of solar cells. A solar‐to‐hydrogen efficiency of 19.68% is achieved, and the performance can be maintained for 20 h without noticeable change. This structure design provides a novel integrated solar water‐splitting system.