Highly Efficient Porphyrin Sensitizers for Dye-Sensitized Solar Cells

In TiO2-based dye-sensitized nanocryst. solar cells, efficiencies of up to 11% were obtained using Ru dyes, but the limited availability of these dyes together with their undesirable environmental impact led to the search for cheaper and safer org.-based dyes. In this Letter, the authors report the synthesis, electronic, and photovoltaic properties of novel green porphyrin sensitizers. All six porphyrin dyes give solar cell efficiencies of ó5%, but the best performing dye under std. global AM 1.5 solar conditions gives a short circuit photocurrent d. (Jsc) of 14.0 ñ 0.20 mA/cm2, an open circuit voltage of 680 ñ 30 mV, and a fill factor of 0.74, corresponding to an overall conversion efficiency of 7.1%, which, for porphyrin-based sensitizers, is unprecedented. This same dye gives an efficiency of 3.6% in a solid-state cell with spiro-MeOTAD as the hole transporting component, comparable to solid-state cells incorporating the best performing ruthenium dyes.