Enhanced efficiency of quantum dot sensitized solar cells using Cu2O/TiO2 nanocomposite photoanodes

Abstract

Several quantum dot sensitized solar cells (QDSSCs) were fabricated by doping Cu2O nanoparticles (NPs) into the TiO2 photoanode pastes in order to improve their efficiencies. The QDSSCs were made using the CuS counter electrode and sulfide/polysulfide electrolyte. The inclusion of Cu2O NPs in the photoanodes of both CdS and CdSe QDSSCs was found to increase the photocurrent and efficiency. The XPS analysis approved that the Cu2O particles were successfully impregnated on the TiO2 NPs. Results indicated that the photovoltaic parameters of the optimized CdSe cell (η = 3.01%, JSC = 10.2 mA cm−2, VOC = 0.59 V, FF = 0.50) were boosted compared with those of the reference cell which was free of Cu2O (η = 1.88%, JSC = 7.0 mA cm−2, VOC = 0.56 V, FF = 0.48) signifying about 60, 46 and 5% improvements in efficiency, current density and open-circuit voltage, respectively. The lowest intensity of the photoluminescence (PL) peak for the cell fabricated using 0.03% Cu2O doped TiO2 suggested that it had the least charge recombination and the easiest electron transfer which was confirmed by the J-V and efficiency data. The electrochemical impedance spectra (EIS) proved that the electron life time was considerably improved by approximately ten times in the optimized cell (τe = 60.0 ms) compared with that of the cell fabricated only using TiO2 (τe = 5.8 ms). Thus, addition of 0.03%wt Cu2O as a dopant was very appropriate to attain suitable photocurrent efficiency for the QDSSCs because it could be used in a minimum amount to improve the electron transport, drop the recombination and increase the cell efficiency.