A Transparent, High‐Performance, and Stable Sb<sub>2</sub>S<sub>3</sub> Photoanode Enabled by Heterojunction Engineering with Conjugated Polycarbazole Frameworks for Unbiased Photoelectrochemical Overall Water Splitting Devices
Lei Wang, Weitao Lian, Bin Liu, Haifeng Lv, Ying Zhang, Xiaojun Wu, Tuo Wang, Jinlong Gong, Tao Chen, Hangxun Xu
Abstract
Abstract Developing low‐cost, high‐performance, and durable photoanodes is essential in solar‐driven photoelectrochemical (PEC) energy conversion. Sb 2 S 3 is a low‐bandgap (≈1.7 eV) n‐type semiconductor with a maximum theoretical solar conversion efficiency of ≈28% for PEC water splitting. However, bulk Sb 2 S 3 exhibits opaque characteristics and suffers from severe photocorrosion, and thus the use of Sb 2 S 3 as a photoanode material remains underexploited. This study describes the design and fabrication of a transparent Sb 2 S 3 ‐based photoanode by conformably depositing a thin layer of conjugated polycarbazole frameworks (CPF‐TCzB) onto the Sb 2 S 3 film. This structural design creates a type‐II heterojunction between the CPF‐TCzB and the Sb 2 S 3 with a suitable band‐edge energy offset, thereby, greatly enhancing the charge separation efficiency. The CPF‐TCzB/Sb 2 S 3 hybrid photoanode exhibits a remarkable photocurrent density of 10.1 mA cm −2 at 1.23 V vs reversible hydrogen electrode. Moreover, the thin CPF‐TCzB overlayer effectively inhibits photocorrosion of the Sb 2 S 3 and enables long‐term operation for at least 100 h with ≈10% loss in photocurrent density. Furthermore, a standalone unbiased PEC tandem device comprising a CPF‐TCzB/Sb 2 S 3 photoanode and a back‐illuminated Si photocathode can achieve a record solar‐to‐hydrogen conversion efficiency of 5.21%, representing the most efficient PEC water splitting device of its kind.