Comparison of TiO2 Nanoporous Films in Hybrid Organic-inorganic Solar Cells

Hybrid metal-oxide: polymer photovoltaic devices offer a promising cheap alternative to conventional photovoltaics and include the advantages of both the inorganic metal-oxide and organic polymer. The polymer functions as the light absorbing and the hole transporting material, while the metal-oxide functions as the electron acceptor and electron transporting material. A main approach to fabricating this type of solar cell involves forming a connected metal-oxide semiconductor layer by sintering metal-oxide nanoparticles to form a randomly arranged nanostructure, and then including the polymer. However several factors limit the performance of this type of solar cell and the need to optimise the structure and the materials of the device has been highlighted in many studies. This work investigates nanoporous TiO2:P3HT solar cells and compares devices fabricated from a commonly employed TiO2 nanoparticle paste (DSL-18NRT) to devices fabricated from a larger particle novel TiO2 nanoparticle paste (DSL-30NRD). Particle size and the resulting pore size of the TiO2 nanostructure is an important factor in improving device performance, as the difficulty of polymer infiltration into the nanostructure is one of the major limiting factors of the performance in this type of hybrid solar cell. With the larger particle paste it was possible to increase the device thickness without compromising device parameters. Multilayer structures, including interface modifying layers such as Z907 dye molecule were investigated for the larger particle photovoltaic device. With interface modification we obtained 0.53% power conversion efficiency in devices fabricated from these larger nanoparticles. With thickness optimisation we obtained a relatively high JSC of 1.46 mA/cm2 for standard TiO2:P3HT devices.