Improved photoactivity of TiO2 photoanode of dye-sensitized solar cells by sulfur doping

Abstract

The photoactivity of the photoanode determines the power conversion efficiency of dye-sensitized solar cells (DSSC). TiO2 has come up as a potential photoanode in DSSC but it has several drawbacks, including large trap density due to lattice defect that influences carrier transport, interfacial charge transfer, and carrier transport. Here we present an effective approach to improve the TiO2 photoanode photoelectrical properties by chalcogenide ion doping, i.e. sulfur (S), that compensates the oxygen vacancy in the TiO2 lattice, enhancing the photoactivity at the visible region, reducing trap density and increasing the photovoltaic process in DSSC device. S doping in the TiO2 lattice was achieved by thiourea treatment. Our result shows that the S doping improves the interfacial charge transfer and reduced the trap density, improving the carrier lifetime and power conversion efficiency. The champion device, S-doped TiO2 with 0.3 M thiourea treatment, produces the DSSC with power conversion efficiency as high as 4.56%, which is two times higher than the DSSC using pristine TiO2. The S doping should find a potential approach for enhancing the photoactivity of the TiO2 photoanode of the DSSC device.