Strategies for Tuning Optoelectronic Properties of TiO2 Nanomaterials for Solar Photovoltaic Studies

Abstract

Third generation solar cells are mainly focusing on the use of nanomaterials as host components for solar-to-electrical conversions. Among the various nanomaterials, TiO2 is one of the most promising candidates used in solar devices due to their remarkable structural and opto-electrical properties. However, bare TiO2 nanomaterials have the various constraints in efficient solar energy conversions. In the present research endeavors, TiO2 nanomaterials have been modified with the different strategies such as dyad anchoring, dye-quantum dot sensitization, composites of carbon nanostructures with sensitizers, metal ion doping with sensitizers so as to tune its optoelectronic properties for efficient solar energy harvesting. In addition, the interconnectivity between the various components and their optoelectronic properties of modified TiO2 for solar energy conversions have been studied in detail. In the dyad system, a supramolecular ruthenium(II)phthalocyanine··peryleneimide (RuPc···PI) has been anchored on the surfaces of TiO2 and thereafter these TiO2-dyad sensitized solar cells have assembled in a bottom-up fashion. Upon photo-irradiation at air-mass (AM) 1.5, the dyad-based solar devices convert solar light to electricity of 2.1%; which is higher than that of individual dyes. In next strategies, the synthesized CdS quantum dots (QDs) have connected electrostatically to the surfaces of TiO2 nanoparticles (NPs) and thereafter, this binary hybrid heterojunction is further self-assembled physically with N719 dye to form ternary TiO2 NPs-CdS QDs-N719 photoelectrodes. These co-sensitization devices reported the solar energy conversion efficiency (η) up to 2.35 %. In addition, anatase TiO2 NPs is anchored on the surface of functionalized carbon nanostructures (MWCNTs or RGO); which is further sensitized with Ru(II) dyes for solar devices having efficiency reached to 6.21%. In another modification, Cr(III) as well as Mo(VI) ions are inserted into TiO2 host lattice and then their composites with CNs are further sensitized for boosting the solar energy conversions and reached up to 7.69 % of efficiency. Figure 1