Regulation of Microstructure and Composition of Cobalt Selenide Counter Electrode by Electrochemical Atomic Layer Deposition for High Performance Dye-Sensitized Solar Cells

By means of electrochemical atomic layer deposition (ECALD), cobalt selenide counter electrodes have been successfully prepared on FTO substrate for the first time. The as-grown films presented amorphous structure and their composition and microstructure could be regulated effectively by adjusting the depositing potential of Se via the route of ECALD. Cycle voltammograms and Tafel polarization measurements revealed that the cobalt selenide counter electrode exhibited an excellent catalytic activity and stability in the I−/I3− system. Due to the more active catalytic sites and less charge-transfer resistance, the Co1.2Se counter electrode yielded faster and more complete reduction of I3− to I− than the Pt and other compositions of cobalt selenide. As a result, the dye-sensitized solar cell based on the Co1.2Se counter electrode yielded a photoconversion efficiency of 9.28%, which improved by 136% than that of the DSSC based on the Pt electrode (6.84%). Taking the facility and cost efficiency into consideration, ECALD has great potential in preparing high efficient counter electrode for high performance DSSCs.