Semi-transparent and stable In2S3/CdTe heterojunction photoanodes for unbiased photoelectrochemical water splitting
Yuan Cai, Shujie Wang, Bin Liu, Gong Zhang, Hui Gao, Tong Yu, Qingfeng Chang, Peng Zhang, Tuo Wang, Jinlong Gong
Abstract
The development of low-cost, high-performance, and stable photoanodes is essential for solar-driven photoelectrochemical energy conversion. In2S3, 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 In2S3/FTO interface as well as the inherent defects in In2S3 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/In2S3 interface to establish an ohmic contact, effectively resolving the conflict between light shielding of metal and the electron collection barrier from In2S3 to FTO. Additionally, the In2S3/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:In2S3/In2S3/CdTe/NiOx/TiO2/Ni semi-transparent photoanode exhibits a photocurrent density of 12.2 mA/cm2 at 1.23 V vs. reversible hydrogen electrode, with stable operation for 60 h. Pairing a back-illuminated Si photocathode with an In2S3/CdTe semi-transparent photoanode enables a solar-to-hydrogen conversion efficiency of 5.10%. Developing low-cost, high-performance, and stable photoanodes is crucial for solar-driven photoelectrochemical energy conversion. Here, the authors report a semi-transparent photoanode design that enhances carrier mobility for unassisted water splitting by using an Ag layer and a p-n heterojunction.