Efficient charge transport in surface engineered TiO2 nanoparticulate photoanodes leading to improved performance in quantum dot sensitized solar cells

Abstract

Cold argon plasma treated TiO2 nanoparticulate photoanodes have been utilized for fabrication of quantum dot sensitized solar cells (QDSSCs). After plasma treatment the TiO2 nanoparticles got assembled in a closely spaced manner with increase in surface roughness factor owing to surface etching by the highly energetic ions, electron and radicals present in the plasma output. The photoanodes possess high inter-particle contact delivering fast charge carrier transport network minimizing the loss of charge carriers. The increase in conductivity was probed through conducting-AFM measurements. This morphological variation significantly inhibits the interfacial recombination by 3.5 times at the TiO2/NC/electrolyte interface as confirmed through electrochemical impedance spectroscopy. Moreover, the increase in Ti3+ as suggested by X-ray photoelectron spectroscopy also contributes in the enhancement of conductivity providing additional electron donor states. The power conversion efficiency increased from 3.65% to 5.01% for CdSe0.4S0.6 alloy nanocrystals (NCs) sensitized solar cells utilizing these plasma treated TiO2 photoanodes. Thus our strategy paves promising direction for the efficiency enhancements in QDSSC devices.