Template Synthesis of CuInS₂ Nanocrystals from In₂S₃ Nanoplates and Their Application as Counter Electrodes in Dye-Sensitized Solar Cells

We report the room temperature template synthesis of CuInS₂ nanocrystals through incorporation of Cu⁺ cations into In₂S₃ nanoplates whose chemical composition has been controlled by varying the amount of copper ions in the reaction mixture. As a result, bandgaps of the resultant CuInS₂ nanoplates can be tuned from 1.45 to 1.19 eV with [Cu]/[In] molar ratios increasing from 0.7 to 2.9, which was demonstrated by the cyclic voltammetry. We explored the use of CuInS₂ nanocrystals as potential counter electrodes in dye-sensitized solar cells, and a power conversion efficiency of 6.83% was achieved without selenization and ligand exchange. The value is comparable with the performance of a control device using Pt as a counter electrode (power conversion efficiency: 7.08%) under the same device architecture.