Relation between charge carrier density and lifetime in polymer-fullerene solar cells

The recombination kinetics of photo-generated charge carriers in polymer-fullerene solar cells has been studied. The transition between bimolecular to monomolecular (trap-assisted) recombination has been investigated by transient open-circuit voltage decay and intensity dependence of open-circuit voltage at different temperatures to quantify the trap delimitation energy. It has been observed that the critical parameter underpinning the transition between bimolecular to monomolecular recombination is the density of photo-generated charge carriers and their lifetime. The correspondence between carrier lifetime and density of photo-carriers has been experimentally observed for the first time. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4746787]