Photoanode engineering of dye-sensitized photovoltaic cells using zinc oxide microstructures for efficient light harvesting applications

Abstract

Several research activities are being pursued to enhance the efficiency of dye-sensitized,photovoltaic cells (DSCs) by designing and synthesizing new sensitizer molecules and electrolyte species, by adopting co-sensitization and co-adsorption or pre-adsorption strategies, and by utilizing different photoanode and counter electrode materials. However, in majority of the breakthrough works, the DSCs utilize conventional bilayer photoanodes constituted by an active layer (AL) containing ~20-30 nm sized TiO2 nanoparticles and a scattering layer (SL) made up of larger sized (~200-400 nm) TiO2 nanoparticles. Meanwhile, several novel dye and electrolyte systems were investigated for DSCs to realize remarkable performances. Recently, the earth abundant copper (Cu(II/I)) metal complexes have been successfully employed in DSCs as electrolytes for achieving remarkable open circuit potentials (VOC ) owing to their highly positive redox potential. DSCs employing Cu(II/I) electrolyte could achieve appreciable power conversion efficiencies (PCEs) and voltages (> 1V) not only under one sun irradiation (AM 1.5G, 100 mW/cm 2), but also under indoor/ambient light illuminations. Since voltage output is crucial for powering smart electronic devices involving sensors and actuators, the Cu(II/I) electrolyte based DSCs can be extensively utilized for indoor photovoltaic and internet of things (IoT) applications. So far, several organic sensitizer molecules have been developed to be used along with Cu(II/I) complex based electrolytes. Nevertheless,the compatibility of Cu(II/I) electrolyte with other photoanode materials and architectures are seldom explored. The present thesis work aims to design and develop novel photoanode architectures for DSCs using ZnO microstructures for attaining enhanced VOC and PCE under indoor (ambient) as well as outdoor (one sun) illumination conditions.