Efficient Polymer Solar Cells Based on M3EH−PPV

We report on polymer blend solar cells with an external quantum efficiency of more than 30% and a high overall energy conversion efficiency (ECE) under white light illumination (100 mW/cm2) of up to 1.7% using a blend of M3EH−PPV (poly[2,5-dimethoxy-1,4-phenylene-1,2-ethenylene-2-methoxy-5-(2-ethylhexyloxy)−(1,4-phenylene-1,2-ethenylene)]) and CN−ether−PPV (poly[oxa-1,4-phenylene-1,2-(1-cyano)ethenylene-2,5-dioctyloxy-1,4-phenylene-1,2-(2-cyano)ethenylene-1,4-phenylene]). We attribute these high efficiencies to the formation of a vertically composition graded structure during spin coating. Photoluminescence measurements performed on the blend layers indicated the formation of exciplexes between both types of polymers, which we propose to be one factor preventing even higher efficiencies.