Investigation on the effect of neodymium ion doping in TiO2 on the photovoltaic performance of dye-sensitized solar cells

Abstract

Titanium dioxide (TiO2), neodymium (Nd3+) doped TiO2 with the doping levels of 0.3% and 0.5% were synthesised by hydrothermal method and were characterized by powder X-ray diffraction (XRD), UV–vis diffused reflectance spectroscopy (DRS), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Ultraviolet X-ray photoelectron spectroscopy (UPS) and high resolution transmission electron microscopy (HRTEM). Doping of Nd3+ ions have been created new surface energy states below the conduction band of TiO2 which mediate the photoinjected electrons through TiO2 network to external load without any impediment. The Fermilevel (Ef) of TiO2 was shifted to downward direction upon Nd3+ ion doping confirmed from UPS analysis. An enhanced photoconversion efficiency (PCE) of 10.7% was achieved for the device fabricated using 0.3% Nd3+ ion doped TiO2 which is higher than that of the device with undoped TiO2 (10.1%). The noticeable increment in the PCE was due to the reduced charge recombination, longer electron lifetime and improved charge injection form LUMO of the N719 dye to the CB of TiO2.