Vanadium oxide as new charge recombination blocking layer for high efficiency dye-sensitized solar cells

Vanadium pentoxide (V2O5) was used as a novel blocking layer in dye-sensitized solar cells (DSCs), leading to a significant efficiency increase from 8.78% to 9.65%. The addition of V2O5 layer to nanocrystalline (nc)-TiO2 increased peak external quantum efficiency (EQE) from 80% to 88-89%. Cyclic Voltammetry analysis indicated a positive shift of Fermi-level in case of TiO2/V2O5 based cells supported by an increase of its capacitance comparing to bare TiO2 based cells. Electrochemical impedance spectroscopy (EIS) results exhibited a 5 times higher charge recombination resistance (Rcr) in V2O5 layer modified DSCs than conventional cells, which indicated that back charge transfer from TiO2 to tri-iodide in the electrolyte was substantially suppressed. Transient photovoltage measurements on conventional and V2O5 layer modified cells were conducted and their decays were fitted to calculate the electron recombination lifetime (TO, which increased by a factor of 3 in V2O5-based DSCs. This indicated that V2O5 significantly reduced the recombination rate at 1i02/electrolyte interface, further supporting that V2O5 functioned as a new effective surface passivation layer. (C) 2014 Elsevier Ltd. All rights reserved.