Semi-transparent and stable In<sub>2</sub>S<sub>3</sub>/CdTe heterojunction photoanodes for unbiased photoelectrochemical water splitting.

Cai, Yuan; Wang, Shujie; Liu, Bin; Zhang, Gong; Gao, Hui; Tong, Yuting; Chang, Qingfeng; Zhang, Peng et al. · Nat Commun · 2025

basic_science · Level V

Where this comes from

Abstract

The development of low-cost, high-performance, and stable photoanodes is essential for solar-driven photoelectrochemical energy conversion. In<sub>2</sub>S<sub>3</sub>, an n-type semi-transparent semiconductor (~2.0 eV), is particularly well-suited as a photoanode in PEC tandem devices. However, the Schottky barrier at the In<sub>2</sub>S<sub>3</sub>/FTO interface as well as the inherent defects in In<sub>2</sub>S<sub>3</sub> suppress charge extraction. This paper describes the design of a semi-transparent photoanode aimed at enhancing carrier mobility for unassisted water splitting. We incorporate a semi-transparent Ag layer at the FTO/In<sub>2</sub>S<sub>3</sub> interface to establish an ohmic contact, effectively resolving the conflict between light shielding of metal and the electron collection barrier from In<sub>2</sub>S<sub>3</sub> to FTO. Additionally, the In<sub>2</sub>S<sub>3</sub>/CdTe p-n heterojunction forms an effective built-in electric field, which serves as a strong driving force for the separation and migration of photogenerated charges. The Ag/Ag:In<sub>2</sub>S<sub>3</sub>/In<sub>2</sub>S<sub>3</sub>/CdTe/NiO<sub>x</sub>/TiO<sub>2</sub>/Ni semi-transparent photoanode exhibits a photocurrent density of 12.2 mA/cm<sup>2</sup> at 1.23 V vs. reversible hydrogen electrode, with stable operation for 60 h. Pairing a back-illuminated Si photocathode with an In<sub>2</sub>S<sub>3</sub>/CdTe semi-transparent photoanode enables a solar-to-hydrogen conversion efficiency of 5.10%.