Dual doping of mesoporous carbon pillars with oxygen and sulfur as counter electrodes for iodide/triiodide redox mediated dye-sensitized solar cells

摘要

Pillar-like mesoporous carbon doped with oxygen and sulfur heteroatoms was obtained through thermal pyrolysis of a zinc-based metal-organic framework, Zn-BTC (BTC = 1,3,5-benzenetricarboxylic acid), followed by acid treatment and sulfurization. The pillar morphology remained after acid etching and sulfur doping, while the content of disordered carbon and the structural defects were significantly increased, resulting in an increase in the electroactive sites for catalyzing the iodide/triiodide ions. In addition, the incorporation of sulfur heteroatoms into carbon frameworks could cause the reduction of oxygen-doped carbon pillars, improving the apparent electrocatalytic activity. The cyclic voltammetry and electrochemical impedance spectroscopy showed that the oxygen and sulfur dual-doped (OS-doped) carbon electrode has better electrocatalytic performance than the single oxygen doped (O-doped) carbon electrode, probably owing to the sulfur doping in carbon matrix that offered abundant electroactive site for boosting the iodide/triiodide redox shuttle. Dye-sensitized solar cell employing OS-doped carbon exhibited power conversion efficiency of 10.2%, greater than that using Pt (9.4%), O-doped carbon (8.0%), and ZnO-doped carbon (7.7%).