Tailoring a Back‐Contact Barrier for a Self‐Powered Broadband Kesterite Photodetector With Ultralow Dark Current Enabling Ultra‐Weak‐Light Detection - Qianfeng Wu; Chuanhao Li; Shuo Chen; Zhenghua Su; Muhammad Abbas; Chao Chen; Qianqian Lin; Jingting Luo; Liming Ding; Guangxing Liang (Carbon Energy, 2025)