Study of band gap reduction of TiO2 thin films with variation in GO contents and use of TiO2/Graphene composite in hybrid solar cell

Abstract

We have successfully designed a hybrid solar cell for improved performance of the P3HT based photovoltaic devices by using TiO2/Graphene composites. There has been significant improvement in IV characteristics of organic solar cells prepared by this method. The TiO2/Graphene composites act as electron collectors in active layer along with P3HT: PCBM in inverted organic photovoltaic devices. The energy bandgap was prominently reduced from 3.00 eV to 2.71 eV as confirmed by cyclic voltametery (CV) and UV-Vis spectroscopy. We have separately synthesized the TiO2 nanoparticles of size range (15 nm-22 nm) through condensed refluxed sol gel method in which titanium isopropoxide was taken as precursor. Modified Hummer's Method was used for the oxidation of graphite flakes into graphene oxide (GO) using KMnO4 as an oxidizing agent. TiO2/Graphene composites were prepared by the subsequent sonication and heating processes. We have rigorously characterized the sample through various characterization tools. Scanning electron microscopy (SEM) results of TiO2/Graphene films reveal the homogenous distribution of graphene nanosheets among the homogenously distributed titanium nanoparticles. X-ray diffraction (XRD) has shown the pure anatase phase peaks of TiO2 nanoparticles and oxidation of graphite at 11.8°. Fourier transform infrared spectroscopy (FTIR) has been used to study the vibrating modes. The chemical bonding Ti-O-C resulted to enhance the electron transport in obtained TiO2/Graphene composite films. UV-Vis spectroscopy has expressed the oxidation peaks of graphite around 216 nm and all composite films were observed in visible region. The significant reduction in band gap and improved performance of hybrid solar cell using TiO2/Graphene composite as electron collector in active layer, is attributed to getting better economical power conversion efficiency solar cell.