Abstract
High-quality titanium dioxide (TiO2 or titania) nanoparticles (TiO2NPs) with tailored morphologies are desirable for efficient photovoltaic applications. In this view, some thin films containing spherical TiO2NPs were prepared on indium tin oxide (ITO) and silicon (Si) substrates from titanium hydroxide Ti(OH)4 using the unified sol-gel, spray and spin coating method followed by thermal annealing at different temperatures (in the range of 200–650 °C). Samples were characterized using various analytical tools to determine the influence of annealing temperatures on their structures, morphologies, and optical and photovoltaic characteristics. A field-emission scanning electron microscope (FESEM) and energy-filtered transmission electron microscopy (EFTEM) images of the annealed films displayed the existence of spherical TiO2NPs of average size in the range of 3.2 to 33.94 nm. XRD analysis of the films showed their amorphous nature with anatase and rutile phase. Optical UV-Vis spectral analysis of the annealed films exhibited a decrease in the bandgap energy from 3.84 to 3.24 eV with the corresponding increase of annealing temperature from 200 to 650 °C. The optimum films obtained at 500 and 600 °C were utilized as electron transport layers to fabricate the metal-insulator-semiconductor solar cells. The cells’ power conversion efficiency assembled with the spherical TiO2NPs-enclosed thin films annealed at 500 and 600 °C were 1.02 and 0.28%, respectively. Furthermore, it was shown that the overall properties and photovoltaic performance of the TiO2NPs-based thin films could be improved via thermal annealing.
Highlights
Among different types of metal oxides, TiO2 is greatly beneficial for various applications, including solar cells, gas sensors, light-emitting diodes (LED), and bactericidal and anti-fungal agents
Heterogeneous solar cells based on TiO2 /Si and ZnO/Si layers have been used to overcome the high recombination rate by producing small conduction band barriers (∆EC ), which enabled the extraction of photo-generated electrons and high valence band barriers
Micrographs together with their particles size distribution of three TiO2 NPs annealed at temperatures of 200, 300, and 400 ◦ C after sonicating the thin film in ethanol to 30 min
Summary
Among different types of metal oxides, TiO2 is greatly beneficial for various applications, including solar cells, gas sensors, light-emitting diodes (LED), and bactericidal and anti-fungal agents. Heterogeneous solar cells based on TiO2 /Si and ZnO/Si layers have been used to overcome the high recombination rate by producing small conduction band barriers (∆EC ), which enabled the extraction of photo-generated electrons and high valence band barriers (∆EV ) that prevented the extraction of the photo-generated hole. These hetero-structured films acted as electrons transport layers (ETLs) or hole blocking layers (HBLs) [8]. Schottky junction metal-semiconductor (MS) solar cells with simple structures can be produced at a low manufacturing cost
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