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A process accumulated record solar to hydrogen (STH) conversion efficiency of 8% is achieved on the Cu2ZnSnS4‐BiVO4 tandem cell by the synergistic coupling effect of solar thermal and photoelectrochemical (PEC) water splitting with the dynamic balance of solar energy storage and conversion of the greenhouse system. This is the first report of a Cu2ZnSnS4‐BiVO4 tandem cell with a high unbiased STH efficiency of over 8% for solar water splitting due to the greenhouse device system. The greenhouse acts as a solar thermal energy storage cell, which absorbs infrared solar light and storage as thermal energy with the solar light illumination time, while thermoelectric device (TD) converts thermal energy into electric power, electric power is also recycled and added onto Cu2ZnSnS4‐BiVO4 tandem cell for enhanced overall water splitting. Finally, the solar water splitting properties of the TD‐Cu2ZnSnS4‐BiVO4 integrated tandem cell in pure natural seawater are demonstrated, and a champion STH efficiency of 2.46% is presented, while a large area (25 cm2) TD‐Cu2ZnSnS4‐BiVO4 integrated tandem device with superior long‐term stability is investigated for 1 week, which provides new insight into photoelectrochemical solar water splitting devices. [ABSTRACT FROM AUTHOR]

The ternary compound photovoltaic semiconductor Cu3BiS3 thin film‐based photoelectrode demonstrates a quite promising potential for photoelectrochemical hydrogen evolution. The presented high onset potential of 0.9 VRHE attracts much attention and shows that the Cu3BiS3 thin films are quite good as an efficient solar water splitting photoelectrode. However, the CdS buffer does not fit the Cu3BiS3 thin film: the conduction band offset between CdS and Cu3BiS3 reaches 0.7 eV, and such a high conduction band offset (CBO) significantly increases the interfacial recombination ratio and is the main reason for the relatively low photocurrent of the Cu3BiS3/CdS photoelectrode. In this study, the InxCd1−xS buffer layer is found to be significantly lowered the CBO of CBS/buffer and that the In incorporation ratio of the buffer influences the CBO value of the CBS/buffer. The Pt‐TiO2/In0.6Cd0.4S/Cu3BiS3 photocathode exhibits an appreciable photocurrent density of ≈12.20 mA cm−2 at 0 VRHE with onset potential of more than 0.9 VRHE, and the ABPE of the Cu3BiS3‐based photocathode reaches the highest value of 3.13%. By application of the In0.6Cd0.4S buffer, the Cu3BiS3‐BiVO4 tandem cell presents a stable and excellent unbiased STH of 2.57% for over 100 h. [ABSTRACT FROM AUTHOR]

A process accumulated record solar to hydrogen (STH) conversion efficiency of 8% is achieved on the Cu 2 ZnSnS 4 -BiVO 4 tandem cell by the synergistic coupling effect of solar thermal and photoelectrochemical (PEC) water splitting with the dynamic balance of solar energy storage and conversion of the greenhouse system. This is the first report of a Cu 2 ZnSnS 4 -BiVO 4 tandem cell with a high unbiased STH efficiency of over 8% for solar water splitting due to the greenhouse device system. The greenhouse acts as a solar thermal energy storage cell, which absorbs infrared solar light and storage as thermal energy with the solar light illumination time, while thermoelectric device (TD) converts thermal energy into electric power, electric power is also recycled and added onto Cu 2 ZnSnS 4 -BiVO 4 tandem cell for enhanced overall water splitting. Finally, the solar water splitting properties of the TD-Cu 2 ZnSnS 4 -BiVO 4 integrated tandem cell in pure natural seawater are demonstrated, and a champion STH efficiency of 2.46% is presented, while a large area (25 cm 2 ) TD-Cu 2 ZnSnS 4 -BiVO 4 integrated tandem device with superior long-term stability is investigated for 1 week, which provides new insight into photoelectrochemical solar water splitting devices., (© 2022 The Authors. Advanced Science published by Wiley-VCH GmbH.)

The ternary compound photovoltaic semiconductor Cu 3 BiS 3 thin film-based photoelectrode demonstrates a quite promising potential for photoelectrochemical hydrogen evolution. The presented high onset potential of 0.9 V RHE attracts much attention and shows that the Cu 3 BiS 3 thin films are quite good as an efficient solar water splitting photoelectrode. However, the CdS buffer does not fit the Cu 3 BiS 3 thin film: the conduction band offset between CdS and Cu 3 BiS 3 reaches 0.7 eV, and such a high conduction band offset (CBO) significantly increases the interfacial recombination ratio and is the main reason for the relatively low photocurrent of the Cu 3 BiS 3 /CdS photoelectrode. In this study, the In x Cd 1- x S buffer layer is found to be significantly lowered the CBO of CBS/buffer and that the In incorporation ratio of the buffer influences the CBO value of the CBS/buffer. The Pt-TiO 2 /In 0.6 Cd 0.4 S/Cu 3 BiS 3 photocathode exhibits an appreciable photocurrent density of ≈12.20 mA cm -2 at 0 V RHE with onset potential of more than 0.9 V RHE , and the ABPE of the Cu 3 BiS 3 -based photocathode reaches the highest value of 3.13%. By application of the In 0.6 Cd 0.4 S buffer, the Cu 3 BiS 3 -BiVO 4 tandem cell presents a stable and excellent unbiased STH of 2.57% for over 100 h., (© 2022 The Authors. Advanced Science published by Wiley-VCH GmbH.)