Unleashing potential of novel 2D-Bi2S3/1D-SnO2heterostructure thin film anodes for light-fostered asymmetric electrochromic supercapacitors

Abstract

In this work, a novel 2D-Bi2S3/1D-SnO2, n–n heterostructure thin film was employed as a pseudocapacitive photoanode for enhanced solar energy utilization, yielding a significant improvement in energy storage performance. The three-electrode system delivered an areal capacitance of 15.22 mF cm−2 in 1 M Na2SO4 electrolyte at 0.2 mA cm−2 under 1 sun illumination, achieving 33% enhancement compared to dark conditions. In addition, the fabricated Bi2S3/SnO2‖PEDOT:PSS asymmetric photo-assisted electrochromic supercapacitor device exhibited a maximum areal capacitance of 1.78 mF cm−2 at 0.06 mA cm−2, which represents a 2.5-fold increase over its performance in the dark (0.70 mF cm−2 at 0.06 mA cm−2). Under illumination, the device also showed an areal energy density (Ea) of 0.8 mWh cm−2 and areal power density (Pa) of 356 mW cm−2. The device retained excellent cycling stability, with capacitance retention of 82.2% and 77.2% at 0.2 mA cm−2 after 1000 GCD cycles under dark and illumination, respectively. Mechanistic investigations revealed that the intercalation/de-intercalation of Na+ ions into 2D Bi2S3 (Bi2S3 + xNa+ + xe− ↔ NaxBi2S3) and SO42− ions into the PEDOT:PSS chain during the charge–discharge process were facilitated by photon-induced redox activity and efficient charge separation by SnO2 nanorods (NRs), thereby improving energy storage capability. This study underscores the potential of novel heterostructure design and material combinations for the development of next-generation photo-rechargeable supercapacitors, paving the way for self-powered electronic devices. This journal is © The Royal Society of Chemistry, 2026