Charge Transfer Excitons in Polymer/Fullerene Blends: The Role of Morphology and Polymer Chain Conformation

Here, it is shown how carrier recombination through charge transfer excitons between conjugated polymers and fullerene molecules is mainly controlled by the intrachain conformation of the polymer, and to a limited extent by the mesoscopic morphology of the blend. This experimental result is obtained by combining near-infrared photoluminescence spectroscopy and transmission electron microscopy, which are sensitive to charge transfer exciton emission and morphology, respectively. The photoluminescence intensity of the charge transfer exciton is correlated to the degree of intrachain order of the polymer, highlighting an important aspect for understanding and limiting carrier recombination in organic photovoltaics.