Thermally activated singlet exciton fission observed in rubrene doped organic films

The magnetic field effects of photoluminescence (MPL) from rubrene doped organic films were recorded at different temperatures. The measured line shapes were attributed to the field modification on the rate constant of thermally activated singlet exciton fission which occurred between the doped rubrene molecules. And its amplitude exhibited a non-linear dependence on the averaged intermolecular distance. Such an observation implies that the intermolecular coupling (IMC) which is modulated by changing the intermolecular distance is able to significantly affect the intensity of fission process. Therefore, investigating the variation of singlet fission with different strength of IMC could be an important means to study the dynamics of fission process. Our work reveals the importance of IMC factor which needs to be considered for the design of efficient singlet fission-sensitized organic photovoltaic devices. (C) 2013 Elsevier B.V. All rights reserved.