Bi 2 S 3 can do it all: Sensitizer, counter electrode, and supercapacitor for symmetric solar cell assisted photo‐supercapacitor

The current research motivation is to fabricate and demonstrate Pt-free dye-sensitized solar cells (DSSCs) at a low-cost and an electrode for supercapacitor. In this study, a well-known sensitizer in quantum dot solar cells, that is, Bi2S3 and Bi2S3/MWCNT hybrids have been synthesized and positioned as an electrocatalyst for the reduction of triiodide to iodide ( I 3 − / I − $$ {I}_3^{-}/{I}^{-} $$ ). Developed DSSC cell-based on Bi2S3/MWCNT counter electrode (CE) achieves a power conversion efficiency of 4.8%, surpassing the corresponding Bi2S3 CE (1.06%) where the efficiency of the present CE yields ~83% of the conventional Pt CE efficiency (~5.8%). In addition, a series of electrochemical investigations reveal that the Bi2S3/MWCNT outperformed the pristine Bi2S3 in terms of electroconductivity and electrocatalytic behavior. This mixture is also favorable for supercapacitors and Bi2S3/MWCNT has the maximum specific capacity of 133 F g−1 with 1 A g−1 in 0.5 M of Na2SO4 with the acceptable capacitance retention of around 80% for 3000 cycles and excellent rate capability (48 F g−1 at 5 A g−1). Besides, the symmetric cell, that is, TiO2/Bi2S3/( I 3 − / I − $$ {I}_3^{-}/{I}^{-} $$ )/Bi2S3 has been manufactured and tested successfully. Thus, Bi2S3 is not only a substitute for the conventional Pt-based CE in DSSCs but also can be a potential energy storage material and sensitizer for photo-supercapacitor applications.