Synthesis of Cu Doped Titania Nanoparticles and Thin Films and Studies on its Structural and Thermal Performance for Dye Sensitized Solar Cells /

Abstract

Fossil energy sources are continuously depleting and causing damage to the environment. Harnessing energy from the alternative sources is answer to challenges posed by the usage of fossil fuels. One of the potential options to mitigate the reliance on fossil fuels is to generate electricity by photovoltaic technologies. Dye Sensitized Solar Cells are among the top candidates with low-cost and with potential to replace the expensive crystalline Si solar technologies. Photoanode is one of the most important components in DSSCs for which oxide ceramics such as titania is one of the top choices. In this work, we have synthesized undoped and doped titania nanoparticles by simple and reliable sol-gel route. Metal doping can introduce structural defects in titania lattice that can result in increase in photocatalytic performance of solar cells. There was an indication in literature that Cu could initiate phase transformation in titania at lower temperature supportive to cell performance. Furthermore, Cu offers its candidature due to being relatively inexpensive and easily available. However, there is not enough data available in literature on performance of DSSCs based on Cu doped titania photoanode. Therefore, we are presenting herein systematic studies on Cu doped titania nanoparticles. Meanwhile, thin film coatings of titania and doped titania were made on FTO coated glass by assortment of methods like spin coating, doctor blade coating, etc. Various process routes such as effects of annealing temperature, Cu concentration, paste precursor and film thickness, film drying time, pore former dye effects, etc. were used in this study. Structural and thermal performance of materials and thin films were carried out using diversified techniques such as X-ray diffraction, Scanning electron Microscopy, TG-DT analysis, Fourier Transform Infrared Spectroscopy (FTIR), etc. Studies have revealed that dopant existed in the form of CuO in nanoparticles and thin films. Cu doping assisted in reduction in particle size and in band gap which was further verified by red absorption shift. Films with almost negligible crack were successfully made on FTO coated glass and it was found that crack density reduced with reducing drying time, increasing stirring time and adding HNO3 along with water and ethanol as a precursor solvent. The inclusion of carbon microspheres formed cavities into the pellets of titania and Cu:TiO2 and increased the porosity and surface area for greater dye adsorption. It was found that porosity increased from 31% to 42% by adding 2.5 wt% carbon microspheres in 3wt% Cu doped titania thin films. IV measurements of the cells fabricated using Cu doped titania photoanode N3 dye, I-/I3- electrolyte and gold coated FTO glass as counter electrode revealed a 11% increase in Voc when compared to Voc of cells made with similar components but using undoped titania photoanode.