文摘
We report a cobalt pyrite (cobalt disulfide, CoS<sub>2sub>) thin film on glass as a robust, high-performance, low-cost, earth-abundant counter electrode for liquid-junction quantum dot-sensitized solar cells (QDSSCs) that employ the aqueous sulfide/polysulfide (S<sup>2鈥?/sup>/S<sub>nsub><sup>2鈥?/sup>) redox electrolyte as the hole-transporting medium. The metallic CoS<sub>2sub> thin film electrode is prepared via thermal sulfidation of a cobalt film deposited on glass and has been characterized by powder X-ray diffraction and electron microscopy. Using the CoS<sub>2sub> counter electrode, CdS/CdSe-sensitized QDSSCs display improved short-circuit photocurrent density and fill factor, achieving solar light-to-electricity conversion efficiencies as high as 4.16%, with an average efficiency improvement of 54 (卤14)% over equivalent devices assembled with a traditional platinum counter electrode. Electrochemical measurements verify that CoS<sub>2sub> shows high electrocatalytic activity toward polysulfide reduction, rationalizing the improved QDSSC performance. CoS<sub>2sub> is also less susceptible to poisoning by the sulfide/polysulfide electrolyte, a problem that plagues platinum electrodes in this application; furthermore, CoS<sub>2sub> exhibits excellent stability in sulfide/polysulfide electrolyte, resulting in highly reproducible performance.
Keywords:
quantum dot-sensitized solar cell (QDSSC); cobalt pyrite (CoS<sub>2sub>); sulfide/polysulfide electrolyte; photovoltaic solar energy conversion; counter electrode; electrochemistry