Preparation and photoelectric properties of Ho3+-doped titanium dioxide nanowire downconversion photoanode

Ho3+-doped titanium dioxide (TiO2:Ho3+) downconversion (DC) nanowires were synthesized through a simple hydrothermal method followed by a subsequent calcination process after being immersed in Ho(NO3)3 aqueous solution. Moreover, TiO2:Ho3+ nanowires (HTNWs) were used as the photoanode in dye-sensitized solar cells (DSSCs) to investigate their photoelectric properties. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the morphology and structure of the material, respectively. The photofluorescence and ultraviolet–visible absorption spectra of HTNWs reveal a DC from the near and middle ultraviolet light to visible light which matches the strong absorbed region of the N719 dye. Compared with the pure TNW photoanode, HTNWs DC photoanodes show greater photovoltaic efficiency. The photovoltaic conversion efficiency (η) of the DSSCs with HTNWs photoanode doped with 4% Ho2O3 (mass fraction) is two times that with pure TNW photoanode. This enhancement could be attributed to HTNWs which could extend the spectral response range of DSSCs to the near and middle ultraviolet region and increase the short-circuit current density (Jsc) of DSSCs, thus leading to the enhancement of photovoltaic conversion efficiency.