Design and fabrication of multi-functional working electrodes with TiO2/CZTSe/bamboo-charcoal-powder composite particles for use in dye-sensitized solar cells

Abstract This study developed a multi-functional electrode with composite particles for use in high-efficiency dye-sensitized solar cells (DSSCs). Photoelectron current was enhanced through the inclusion of the visible light absorber Cu 2 ZnSnSe 4 (CZTSe) as well as narrow band gap carbon-doped TiO 2 in conjunction with a novel dye absorber, bamboo charcoal powder (BCP). Photoelectron voltage was maintained at a high level through the inclusion of a p–n junction (CZTSe–TiO 2 ). The CZTSe was synthesized using a solvo-thermal process that does not require an autoclave, and BCP was obtained from dehydrated bamboo charcoal. Composites of TiO 2 (P-25)/BCP, TiO 2 (P-25)/CZTSe, and TiO 2 (P-25)/CZTSe/BCP were prepared by wet ball mill grinding prior to the fabrication of DSSC working electrodes. The band gap of the TiO 2 (P-25)/CZTSe electrode was shown to decrease with an increase in the quantity of CZTSe; dropping from 2.92 to 2.32 eV when the mass ratio of TiO 2 to CZTSe changed from 10:0.1 to 10:0.9. Calculations based on density functional theory reveal unintentional substitutions of Cu (to Ti) and Se (to O) atoms contribute to the narrowing of original TiO 2 band gap. We also measured the cell performance, including short-circuit photocurrent density ( J sc ), open-circuit photovoltage ( V oc ), and power conversion efficiency ( η ). The η of DSSCs (6.85%) with a TiO 2 (P-25)/CZTSe/BCP electrode (TiO 2 :CZTSe:BCP = 10:0.3:0.6) far exceeded that of conventional DSSCs with a TiO 2 (P-25) electrode (3.84%). Of particular note is the fact that the V oc and J sc of the proposed DSSC exceed those of conventional devices by 9.5% and 100%, respectively. The principles used in the design of the proposed electrode could be extended to all photovoltaic devices.