One of the most reliable renewable energy source is the solar energy from the sun. However, most materials have been unable to meet their potentials as a good absorber layer in thin films. Most recently, Cu2ZnSnS4 (CZTS) have been identified as a good absorber layer, yet the same problem persists. In this study, we examined the depletion capacitance vis-a-vis the voltage and range of frequencies based on heterojunction types and structures. The modeled solar cell consisted three types of materials used as buffer layer (BL) (ZnO:Al (AZO), In2S3 (IS) and CH3NH3PbCl3 (PVKT)). The band gap model of n/n/p anisotype heterojunction for the three BLs were constructed from the obtained data of the simulated solar cells. The band offsets ∆EC and ∆EV in electron-volts at n/n for AZO, IS and PVKT are; 0.07071 and 0.18794, 0.09768 and 0.72367 and 0.67541 and 2.54541 respectively. Also, at n/p ∆EC and ∆EV for AZO, IS and PVKT are; 0.14251 and 1.93251, 0.49011 and 1.73011 and 0.34041 and 1.73920 respectively. Based on the trivial AC signal that was superimposed on the dc biased charges, AZO and IS shows an exponential response of the capacitance reliance on the voltage across the depletion region. The Capacitance spectroscopy of this solar cell showed that anisotype heterojunction may be manipulated to make use of the voltage reliance on junction capacitance when the need to electronically vary it arises.

This work focuses on the sol-gel spin coating technique of TiO 2 nanostructure synthesis and its characterization. Though various methods have been used to fabricate TiO 2 nanostructure, much effort has not been exerted to achieve better photoresponsive and narrowly dispersed TiO 2 nanostructure using the sol-gel spin coating method. Therefore, it is imperative to realize the synthesis of TiO 2 nanostructures, and investigate their properties. In this work, TiO 2 is synthesized by sol-gel spin coating technique using titanium tetraisopropoxide, isopropanol, acetic acid and deionized water as starting materials and deposited on borosilicate glass substrates. The effects of annealing temperatures (300˚C, 400˚C and 500˚C) on the structural and optical properties of the films were investigated by different techniques: Scanning Electron Microscopy (SEM), optical microscopy and UV-visible spectrophotometry. The optical characterization showed the direct band gap at 3.7 eV, 3.6 eV and 3.4 eV for 300˚C, 400˚C and 500˚C, respectively, and the optical transmittance and reflectance spectra showed a greater performance at 500˚C. The grain sizes obtained from SEM annealed at 300˚C, 400˚C and 500˚C are found to be about 6.0 nm, 5.0 nm and 4.0 nm respectively. The grain size of TiO 2 nanostructure films decreased with increasing annealing temperatures. The results clearly indicated that the sol-gel spin coating synthesis of TiO 2 nanostructure and post-thermal treatment at 500˚C cooled naturally at room temperature result in better photoresponsive and narrowly dispersed TiO 2 nanostructure films with higher photoresponsive and good optical properties.