Enhanced photovoltaic performance of CdSe quantum dot-sensitized solar cells with Eu-doped TiO2 photoanode

In this work, different percentages of Eu-doped TiO2 nanoparticles were synthesized by sol–gel method. The bandgap and conduction band minimum (CBM) of TiO2 nanoparticles doped by 0.075 at% Eu element is reduced from 3.43 and – 3.93 eV to 3.09 and – 4.25 eV, respectively, deduced from the results of ultraviolet–visible (UV–Vis) absorption spectroscopy and ultraviolet photoelectron spectroscopy (UPS) measurement compared with un-doped TiO2. As the increase of Eu concentration, short-circuit photocurrent density Jsc of CdSe quantum dot-sensitized solar cells (QDSCs) increases from 10.86 to 13.86 mA/cm2, while open-circuit voltage Voc is almost invariable. Optimal power conversion efficiency (PCE) of 4.03% is achieved for CdSe QDSCs with 0.075 at% Eu-doped TiO2 film. Compared with un-doped devices, the decrease of the chemical capacitance Cμ and the increase of recombination resistance Rrec of QDSCs based on the 0.075 at% Eu-doped TiO2 photoanodes can facilitate charge extraction and suppress charge recombination at the TiO2/electrolyte interface.