Composite multi-functional over layer: A novel design to improve the photovoltaic performance of DSSC

Light scattering in dye-sensitized solar cell (DSSC) plays a vital role in extending the traveling distance by confining light propagation within the photoanode and also promotes interaction of incident photons with the dye molecules. A novel strategy was adopted to improve the performance of DSSC with better absorption of solar spectrum both in the visible as well as near IR regions. A double layer photoanode structure with TiO2 nanoparticles (P25) as main layer and composite of titanium nanotubes (TNTs) and P25 as over-layer was introduced. Three different compositions of TNT/P25 were investigated, and finally an optimized composition with excellent performance was prepared. Performance of cells having composite over-layer was compared with the cells having TNT and conventional bigger particles (G2) over-layers. Composite over-layer structure of 75/25-TNT/P25 showed best photovoltaic performance of 8.52% with J(sc) of 16.49 mA/cm(2), which is 7.30% higher than the cells having G2 over-layer and 4.9% higher than the cells having pure TNT over-layer. Different characterization analysis proved that DSSC with optimized composite over-layer structure has significant advantages of better dye adsorption, large surface area, better photo-electron generation, superior electron recombination restraint characteristics, better conductive behavior, better light scattering, and long electron lifetime. Composite over-layer structure is a promising and innovative approach for further improving the efficiency of DSSC and this will be a concrete fundamental background toward the development of the applications of the next generation dye-sensitized solar cells. (C) 2015 Elsevier B.V. All rights reserved.