Design of high-efficiency dye-sensitized nanocrystalline solar cells

Yavuz, Halil İbrahim
Nanocrystalline dye sensitized solar cells (DSSC) technology continues to develop as a better alternative to the silicon based solar cells, which are commercialized. This study aims at finding low cost and highly efficient DSSC design and production methods via examination of effects of both photoanode structure and photon-electron generation mechanism on photoanode layers. This will contribute to the commercialization of DSSC technology. Photoanode structure is examined in four groups; transparent conductive glass (TCO), blocking layer (BL), absorber layer (AL) and scattering layer (SL) throughout this study. Firstly, indium doped SnO2 (ITO) was synthesized by sol-gel method for the use in TCO part of the DSSCs. 4.32% conversion efficiency has been found by using those TCO’s in the production of fully sol-gel based DSSCs. For the first time in the literature, 1D ITO structures were synthesized by sol-gel method and this synthesis was used on DSSCs in order to increase the interaction between TCO and AL. However, the commercialized fluorine doped SnO2 (FTO) TCO’s were used instead of ITO based ones in the rest of the study since their charge transport resistances are lower. ZrO2 BL was found to have superior photovoltaic characteristics in prevention of back transfer reactions. In addition, ZrO2 BL was found to protect the conductivity of FTO based TCO’s during heat treatment. AL, which is responsible for photon to electron generation, was synthesized using 5% Zr doped TiO2 nanoparticles. This synthesis was found to have photon to energy conversion efficiency (ɳ) trice than bare TiO2 absorber layer. Moreover, adding hydrothermal treatment step to the sol-gel method process was found to increase photon to energy conversion efficiency rate. The scattering layers enable to increase the light absorption ability of DSSC via unused photons scattering back to metal oxide sensitized interface. For this purpose, SL was produced by 10% Zr modified TiO2 particles. These particles showed better performance rate than traditionally produced scattering layer. As a result of all these analyses, this Thesis found that the modifications made to the photoanode increased DSSC’s photovoltaic characteristics. After the modifications 7.45% photon to energy conversion efficiency was obtained.
Citation Formats
H. İ. Yavuz, “Design of high-efficiency dye-sensitized nanocrystalline solar cells,” Ph.D. - Doctoral Program, Middle East Technical University, 2014.