Advanced Semiconductor Architectures for Fast Electron Transport – By Venkata and Juanpa
Conventional dye sensitized solar cells use TiO2 naoparticles for the photoanode. The transport is slow in TiO2 nanoparticulate film due to trapping of the electrons in the grain boundaries and the relatively long and tortuous path of the electron to the FTO. In a 10 µm thick film of nanoparticles an electron visits about 106 nanoparticles on average before reaching the FTO surface. Different nanoarchitectures are being developed in our lab to take advantage of fast electron transport, high surface area and dye compatibility of the TiO2 nanoparticles. These projects include:
- ZnO Nanorod- TiO2 Nanoparticle Hybrid where nanorod density and diameter are controlled. Optimization of the ZnO nanorod growth process allows maximizing surface area while leaving sufficient distance between rods for effective TiO2 deposition. Our group is working on different ways to synthesize ZnO seeds, seed coating techniques (spin coating & drop coating), and additives to control the density of ZnO nanorods. ZnO nanorods are grown by chemical bath deposition due to its low temperature, low cost, flexible substrate growth and large area processing suitable for industrial applications.
- Fluorine-doped Tin Oxide (FTO) Aerogels coated with a thin layer of TiO2. The high surface area is an intrinsic property of the aerogel and coating this mesoporous structure must be done in a meticulous way in order to impede large recombination with the electrolyte.
Dye-Anchored Nanocatalyst for Overpotential Reduction – By Perry
The traditional electrolyte for dye sensitized solar cell is iodine/triodine which possesses a 0.5-0.6V of overpotential in order to regenerate dye. The high overpotential is due to highly oxidizing intermediates formed in the multi-step two electrons conversion of I- to I3-. This causes a great loss of open circuit voltage in the cell. The idea is to introduce a noble metal nanocatalyst which can be attached to the dye molecules to lower the driving force of dye regeneration process to reduce the redox potential difference between dye and electrolyte, so that a dye with higher HOMO level and the same LUMO level as traditional N719 dye could be used which can absorb more light, thus affording significant improvements in DSC efficiency. This work will employ catalysis to remove a longstanding limitation on the energy conversion efficiency of low-cost dye-sensitized solar cells.