Dye-sensitized solar cells based on a single layer deposition of TiO2 from a new formulation paste and their photovoltaic performance

Abstract

A new strategy for enhancing the efficiency and reducing the production cost of TiO2 solar cells by design of a new formulated TiO2 paste with tailored crystal structure and morphology is reported. The conventional three- or four-fold layer deposition process was eliminated and replaced by a single layer deposition of TiO2 compound. Different TiO2 pastes with various crystal structures, morphologies and crystallite sizes were prepared by an aqueous particulate sol–gel process. Based on simultaneous differential thermal (SDT) analysis the minimum annealing temperature to obtain organic-free TiO2 paste was determined at 400°C, being one of the lowest crystallization temperatures of TiO2 photoanode electrodes for solar cell application. Photovoltaic measurements showed that TiO2 solar cell with pure anatase crystal structure had higher power conversion efficiency (PCE) than that made of pure rutile-TiO2. However, the PCE of solar cells depends on the anatase to rutile weight ratio, reaching a maximum at a specific value due to the synergic effect between anatase and rutile TiO2 nanoparticles. Moreover, it was found that the PCE of solar cells made of crystalline TiO2 powders was much higher, increasing in the range 32–84% depending on anatase to rutile weight ratio, than that of prepared by amorphous powders. TiO2 solar cell with the morphology of mixtures of nanoparticles and microparticles had higher PCE than the solar cell with the same phase composition containing TiO2 nanoparticles due to the role of TiO2 microparticles as light scattering particles. The presented strategy would open up new insight into fabrication and structural design of low-cost TiO2 solar cells with high power conversion efficiency.