Analysing organic solar cell blends at thousands of degrees per second

Organic photovoltaics (OPVs) can still only achieve efficiencies below those of conventional silicon photovoltaics. To date the highest OPV efficiencies have been found for so-called bulk-heterojunction (BHJ) solar cells, where the active layer is a bi-continuous composite of donor (a conjugated polymer) and acceptor (a small molecule) phases. As in conventional polymer blend systems, the morphology formed will strongly influence the material characteristics, and post-production annealing has been shown to increase device efficiencies.
In this study, the active layer of BHJ devices is analysed using fast-scanning calorimetry techniques in order to investigate the transitions that play a role in stability and morphology development. In particular, Rapid Heat-Cool Calorimetry (RHC) [1], and fast scanning differential chip calorimetry (FSDCC) were used. FSDCC especially shows great potential for these systems due to the very high scanning rates and the ability to study thin layer samples, like in actual BHJ devices.