Enhancing the electron lifetime and diffusion coefficient in dye-sensitized solar cells by patterning the layer of TiO2 nanoparticles

Abstract

In order to fulfill fast electron transport and low recombination rate in dye-sensitized solar cells, we propose to utilize a micro-patterned anode based on TiO2 nanoparticles. The micro-structures of the mesoporous TiO2 films were patterned by Si molds (microimprint technique). A series of measurements including the time of flight, open circuit voltage decay, and charge extraction is carried out to investigate the electron transport in these structures. Our measurement confirms the fast electron transport and high electron lifetime in the micro-patterned structures, which is in agreement with the previously reported simulations. The results have shown that for columnar 20 × 20 μm2 micro-structures, the electron diffusion coefficient is increased by 60% from 3.9 × 10−5 cm2/s to 6.3 × 10−5 cm2/s. In addition, the electron lifetime has considerably (about one order of magnitude) increased in the cells based on TiO2 micro-structures. These enhancements in the electron transport have significantly improved the power conversion efficiency of dye-sensitized solar cells, which is increased by 69% from 5.16% to 8.73%. The results are explained in terms of directional diffusion and extra trap states in the micro-structures of porous TiO2 films.