Intensity dependent but temperature independent charge carrier generation in organic photodiodes and solar cells

Measurements of the transient photoresponse of organic photodiodes and solar cells show a strong saturation effect in the quantum efficiency at laser fluences above approximately 3.3 μJ/cm2. By a comparison of the measured intensity, temperature and field dependence of the transient pulse responses with extended drift–diffusion simulations, the loss of charge carriers can be traced back to a quadratic loss channel in the charge carrier generation process. In contrast to the predictions of the commonly used Onsager–Braun charge carrier generation model, we demonstrate that the dissociation of bound electron–hole-pairs is temperature independent but slightly field dependent.

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► Measurement and simulation of the pulse response of organic solar cells and photodiodes.
► Measured nonlinear loss of extracted charge carriers.
► Loss traced back to bimolecular recombination of charge transfer excitons (CTs).
► CT-dissociation identified to be slightly field dependent but temperature independent.