Low band-gap polymeric photovoltaic devices

We present results on photovoltaic devices based on novel thiophene-isothia naphthene copolymers (PDTI) with pi-pi* band-gaps ranging from 1.2 eV to 1. 8 eV. Single-layer photovoltaic devices were fabricated from films of PDTI doped with a soluble fullerene derivative [6,6]-phenyl-C-61-butyric-acid-me thyl-ester (PCBM) as the electron acceptor and blended into poly(methyl met hacrylate) to enhance the film quality. These devices exhibit spectral resp onse extending into the infrared and are better matched to the solar spectr um as compared to standard PPV based ones. Such low band-gap materials also make possible the construction of dye-sensitized photovoltaic devices that take advantage of energy transfer from high energy absorbing dyes to the h ost polymer.