High conductive Cu3SnSXSe4-X counter electrodes for dye-sensitized solar cells

• Nano crystalline Cu 3 SnS X Se 4-X CEs were synthesized and characterized. • The thickness of Cu 3 SnS X Se 4-X CE was optimized to 1.7 μm. • Photovoltaic efficiency of 7.57% of DSSC with Cu 3 SnS X Se 4-X CE was achieved. Orthogonal Cu 3 SnS 4 (CTS) nano-crystalline were synthesized. It is clarified that Cu 7 S 4 seeds first nucleated in the solvothermal process at 130 °C. When the temperature elevated to 180 °C, Sn 4+ began to enter the Cu 7 S 4 lattice to form orthorhombic CTS nano-crystals. Secondary phase of SnS occurred at 200 °C and could not be eliminated by prolonging heating time. The as-prepared CTS@SnS nano-crystals were selenized at 500 °C for 20 min to form CTS X Se 4-X . The SnS were completely eliminated and main S sites in CTS were substituted by Se anions during the selenization. The CTS X Se 4-X films with different thickness were used as counter electrodes (CEs) of dye-sensitized solar cells (DSSCs). CTS X Se 4-X CEs have good conductivity and effective electrocalalytic activity for I 3 - reduction. In the optimal case of 1.7 μm thick CTS X Se 4-X CE, power conversion efficiency of 7.57% was achieved which is 88.6% of that of the same structural device with commercial Pt CE.