Relationship between the VOC Tuning Effect and the Interface Activation Energy Due to the Third Component Concentration in Ternary Organic Solar Cells

The open-circuit voltage (VOC) tuning effect due to the variation of the low concentration of the third component in ternary organic solar cells has been mainly attributed to interfacial phenomena. Up to date, the models reported in the literature to analyze such interfacial phenomena are based on optical characterization. In this work is proposed a different approach to study such a VOC tuning effect by using dark-current characteristics at different temperatures. Specifically, for PTB7-Th:PC71BM:ICBA-based solar cells, it is found that an increment of the third component concentration, that is, the fullerene ICBA, causes an increase in the activation energies (Ea) in an Arrhenius-type curve. This, in turn, decreases the reverse saturation current (J0) of the devices, thereby incrementing their VOC.