Modeling the temperature induced degradation kinetics of the short circuit current in organic bulk heterojunction solar cells

In organic bulk heterojunction solar cells, the nanoscale morphology of interpenetrating donor-acceptor materials and the resulting photovoltaic parameters alter as a consequence of prolonged operation at temperatures above the glass transition temperature. Thermal annealing induces clustering of the acceptor material and a corresponding decrease in the short circuit current. A model based on the kinetics of Ostwald ripening is proposed to describe the thermally accelerated degradation of the short circuit current of solar cells with poly(2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene) (MDMO-PPV) as donor and (6,6)-phenyl C61-butyric acid methyl ester (PCBM) as acceptor. The activation energy for the degradation is determined by an Arrhenius model, allowing to perform shelf life prediction.