Development of Nanopatterned Photonic Crystal Fluorine-doped Tin Oxide Electrode for High-efficiency Dye Sensitized Solar Cells

Transparent conductors (TCs) are an important component of optoelectronic devices and nanoscale engineering of TCs is important to optimization of the device performance. Despite being a commonly used TC in photovoltaic devices, fluorine-doped tin oxide (FTO) has limited transmittance in solar spectrum. Improving the light transmittance and light scattering properties of FTO may lead to increased light absorption in the active volume of the photovoltaic device. In this work, patterned periodic arrays of nanopillars and nanolines of pitch size of ~700 nm were created on FTO using nanoimprint lithography and reactive ion etching using environmentally friendly gases. The patterned FTO photonic crystal exhibits enhanced light scattering as compared to the unpatterned FTO, which agrees well with simulations based on Finite Difference Time-Domain method. Dye sensitized solar cells fabricated on the patterned FTO exhibited improved performance (fill factor and efficiency), which can be attributed to enhanced incident photon to-current conversion in the range 400 - 650 nm as suggested also by theoretical simulations.