Highly efficient porphyrin sensitizers for dye-sensitized solar cells

Abstract

In TiO2-based dye-sensitized nanocrystalline solar cells, efficiencies of up to 11% have been obtained using Ru dyes, but the limited availability of these dyes together with their undesirable environmental impact have led to the search for cheaper and safer organic-based dyes. In this Letter, we report the synthesis, electronic, and photovoltaic properties of novel green porphyrin sensitizers. All six porphyrin dyes give solar cell efficiencies of >5%, but the best performing dye under standard global AM 1.5 solar conditions gives a short circuit photocurrent density (jsc) of 14.0 ± 0.20 mA/cm2, an open circuit voltage of 680 ± 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. © 2007 American Chemical Society.