Performance of dye-sensitized solar cell fabricated using titania nanoparticles calcined at different temperatures

Synthesis of titania (TiO2) nanoparticles by sol-gel method and their calcination at different temperatures, viz 450 °C, 550 °C and 650 °C (defined as T450, T550 and T650) has been done. Structural analysis indicates that the T450 sample possesses anatase phase. The phase transformation to rutile starts occurring at T550, and, on increasing the calcination temperature, the crystallization and percentage of rutile phase increases. As the temperature increases from 450 to 650 °C, the crystallite size increases by about a factor of two from 11.5 to 20.2 nm. From SEM micrographs, T550 electrode has been found to have appropriate aggregation, which led to enhanced dye desorption, as compared to T450 and T650 based electrodes. TEM images of the synthesized nanoparticles reveal that the particle size increases from 7 to 28 nm on increasing the calcination temperature from 450 to 650 °C. From the photoluminescence and Fourier transform infrared studies, it has been concluded that the surface OH− groups are reduced on calcination, which affects the electron injection efficiency. The dye sensitized solar cell, fabricated using T550 sample, having a ratio of anatase/rutile 89:11, has been found to achieve the highest conversion efficiency.