Ternary organic photodetectors based on pseudo-binaries nonfullerene-based acceptors

The addition of a third component to a donor:acceptor blend is a powerful tool to enhance the power conversion efficiency of organic solar cells. Featuring a similar operating mechanism, organic photodetectors are also expected to benefit from this approach. Here, we fabricated ternary organic photodetectors, based on a polymer donor and two nonfullerene acceptors, resulting in a low dark current of 0.42 nA cm-2 at -2 V and a broadband specific detectivity of 1012 Jones. We found that exciton recombination in the binary blend is reduced in ternary devices due to the formation of a pseudo-binary microstructure with mixed donor-acceptor phases. With this approach a wide range of intermediate open-circuit voltages is accessible, without sacrificing light-to-current conversion. This results in ternary OPD with improved R values in the NIR. Moreover, morphology analyses reveal that ternary OPD devices showed improved microstructure ordering and consequentially higher charge carrier mobilities compared to the reference devices.