Sulfur-doped porous carbon as metal-free counter electrode for high-efficiency dye-sensitized solar cells

In this study, we demonstrate a high performance of sulfur-doped porous carbon (S-PC) as metal-free low-cost counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). The S-PC material is synthesized by using pitch as carbon source and basic magnesium sulfate (BMS) whiskers as both template and S source. The doped sulfur is mainly present in the C-S-C configuration. The enhanced electrocatalytic performance can be attributed to the S atoms doped into the carbon framework which has large effective surface areas due to their porous or rough morphology. Therefore, it enhances the asymmetry of the atomic charge density in C atoms, leading to a large number of reduction sites and low charge transfer resistance. The S-PC significantly enhances the performance compared to the pure porous carbon (PC) due to the lower charge-transfer resistance. The DSSC with S-PC as the CE exhibits a high conversion efficiency of 6.97% which is comparable to that of the traditional Pt CE (7.28%).