Aqueous Selenium Ion Engineering: A Universal Strategy to Reverse Gradient Limitations in Sb <sub>2</sub> (S,Se) <sub>3</sub> Photovoltaics for Enhanced Carrier Dynamics and Performance
Junwei Chen, Gaoyang Li, Chenlong Gao, Shuwei Sheng, Chengwu Ruan, Yichao Wang, Zhiheng Xu, Rongfeng Tang, Chong Chen, Yan Zhang, Tao Chen, Jun Xu
Abstract
Abstract Antimony selenosulfide (Sb₂(S,Se)₃) is a promising earth‐abundant photovoltaic material owing to its excellent optical and electrical properties. Currently, solution‐processed Sb₂(S,Se)₃ photovoltaics face a critical selenium paradox: uncontrolled gradient formation induces band misalignment while creating sulfur vacancies ( V S ) and antimony antisites (Sb S/Se ). Here, an ambient aqueous selenide ion treatment (ASIT) acting as atomic‐scale “ionic scalpel” is pioneered that surgically reconstructs selenium distribution. Through room‐temperature ionic diffusion, this liquid‐phase ion engineering achieves dual breakthroughs: 1) Gradient reversal via surface and bulk selenium enrichment flattening valence band offset from 0.12 to 0.03 eV and establishing ideal Type‐II band alignment, 2) Autogenous deep‐level defects healing via Se−V S /Sb S bond reconfiguration. Significantly, time‐resolved photoluminescence (TRPL) characterization unveils, for the first time, the ultrafast charge‐transfer dynamics at the heterointerface of CdS/Sb₂(S,Se)₃ films fabricated via the ASIT strategy. Ultimately, the resultant Sb₂(S,Se)₃ solar cell shatters performance ceiling with a 10.38% efficiency and record open‐circuit voltage of 0.694 V, showing 57% carrier lifetime enhancement. The water‐based process compatibility with roll‐to‐roll manufacturing positions ASIT as a game‐changer for scalable production of gradient‐engineered absorbers beyond antimony‐based systems.