Development of solution processed Photo-anode based on Graphene-Nb2O5 nanocomposite and RF sputtered Si nanoparticles for dye-sensitized solar cells (DSSCs)

Abstract

Dye-Sensitized Solar Cells (DSSCs) have combined the benefits of both organic as well as inorganic compounds. Ceramic DSSC photo-anode specially Nb2O5 is attracting attention due to higher conduction band edge, higher open circuit voltage (VOC) and most importantly, a lesser charge recombination rate. To improve the charge collection efficiency, an adopted methodology is the introduction of a strong electrically conductive carbon material. Graphene is a high strength material and possessing higher electronic conductivity and large specific surface area. In current study, wet chemistry, modified Hummer’s method and hydrothermal processes were applied for the synthesis of the Nb2O5 nanoparticles, graphene, and Graphene-Nb2O5 nanocomposite respectively. Meanwhile, thin film coatings of Nb2O5 nanoparticles and Graphene-Nb2O5 nanocomposite were deposited on FTO-coated glass substrate by spin coating. The structural and thermal performance of materials and thin films were carried out using diversified techniques such as X-ray diffraction, Scanning electron microscopy, UV-Vis spectroscopy, TG-DT analysis, Fourier Transform Infrared spectroscopy (FTIR) etc. Studies revealed the formation of impurity-free crystalline orthorhombic phase nanoparticles and nanocomposite. We found that the inclusion of graphene not only improved the absorption, it also decreased the band gap causing an increase in the electrical conductivity. Spherical morphology and size of nanoparticles and nanocomposite were confirmed through SEM results. Furthermore, IV measurements of the cells fabricated using Graphene-Nb2O5 nanocomposite photo-anode, N3 dye, I-/I3- electrolyte and gold coated FTO glass as counter electrode revealed the 68% increase in fill factor and 52% increase in efficiency when compared to cells made with similar components but using Nb2O5 nanoparticles as photo-anode. Besides the implementation of ceramic oxides as an electrode in DSSC, inorganic materials like Si has also the potential to employ in DSSC assembly. In fact, researchers have used Si nanoparticles as the counter electrode in DSSC due to better electrocatalytic activity and large intrinsic surface area. The Si nanoparticle has been fabricated by application of high-pressure RF magnetron sputtering process. Various process parameters such as pressure, power and deposition were studied for nanoparticle growth. The experimental conditions were optimized. AFM verified the formation of amorphous Si nanoparticles.