Tailoring a Back-Contact Barrier for a Self-Powered Broadband Kesterite Photodetector With Ultralow Dark Current Enabling Ultra-Weak-Light Detection

Visible and near-infrared photodetectors are widely used in intelligent driving, health monitoring, and other fields. However, the application of photodetectors in the near-infrared region is significantly impacted by high dark current, which can greatly reduce their performance and sensitivity, thereby limiting their effectiveness in certain applications. In this work, the introduction of a C 60 back interface layer successfully mitigated back interface reactions to decrease the thickness of the Mo(S,Se) 2 layer, tailoring the back-contact barrier and preventing reverse charge injection, resulting in a kesterite photodetector with an ultralow dark current density of 5.2 × 10 −9 mA/cm 2 and ultra-weak-light detection at levels as low as 25 pW/cm 2 . Besides, under a self-powered operation, it demonstrates outstanding performance, achieving a peak responsivity of 0.68 A/W, a wide response range spanning from 300 to 1600 nm, and an impressive detectivity of 5.27 × 10 14 Jones. In addition, it offers exceptionally rapid response times, with rise and decay times of 70 and 650 ns, respectively. This research offers important insights for developing high-performance self-powered near-infrared photodetectors that have high responsivity, rapid response times, and ultralow dark current.