Abstract
Exciton dissociation between donor and acceptor is the decisive process to determine the photovoltaic performance of organic solar cells (OSCs). The rather fast dynamics of photo-induced charge generation in well-optimized bulk heterojunction (BHJ) composites complicate the quantitative analysis of the charge generation efficiency for donor and acceptor units. Herein, we report time-resolved photoluminescence (TRPL) investigations and demonstrate their potential as a quantitative and contactless characterization technique allowing to separately determine the exciton splitting efficiency of donor and acceptor moieties in selected single component materials. We demonstrate that the exciton splitting efficiency for donor or acceptor moieties can be separately adjusted in these materials by post-treatment, while the corresponding BHJ composites undergo excessive phase separation upon external stress. By relating the separate exciton splitting efficiencies to their photovoltaic performance, the limiting factor in corresponding OSCs, either charge generation or recombination, is identified.