Development of copper doped titania based photoanode and its performance for dye sensitized solar cell applications

Abstract

Photoanode is one of the most important components in dye-sensitized solar cells (DSSCs) for which oxide ceramics are among the top choices. It has been established that the metal doping can introduce structural defects in oxide ceramics such as in titania lattice which can result in increase in photo-absorption of solar cells. Metals such as Cu being inexpensive and readily available, have potential to cause phase transformation in titania at lower temperature supportive to cell performance. However, there is not enough data available in the literature on performance of DSSCs based on Cu-doped titania photoanode. In this work, we have synthesized undoped and doped titania nanoparticles by wet-chemistry routes. Various process routes such as effects of annealing temperature, Cu concentration, pore former, etc. were employed to investigate the structural, thermal and electrical performance of doped and undoped materials and thin films for DSSCs. For qualitative and quantitative analyses, techniques such as X-ray diffraction, scanning electron microscopy, thermal analyses, molecular spectroscopy and potentiostat were employed. 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 band gap, which was further verified by red absorption shift. IV measurements of the cells fabricated with Cu-doped titania photoanode, N3 dye, I−/I3− electrolyte and gold coated FTO counter electrode, revealed an 11% increase in Voc, compared to Voc of cell made with similar components but using undoped titania photoanode. The inclusion of carbon microspheres caused formation of cavities into the photoanode made with titania and Cu:Titania and increased the porosity and surface area for greater dye adsorption. It was found that porosity increased from 31% to 42% by adding in-house fabricated 2.5 wt% carbon microspheres into 3 wt% Cu-doped titania thin films.