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High-Performance Phototransistors Based on PDIF-CN2 Solution-Processed Single Fiber and Multifiber Assembly

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journal contribution
posted on 29.03.2016, 00:00 by Wassima Rekab, Marc-Antoine Stoeckel, Mirella El Gemayel, Marco Gobbi, Emanuele Orgiu, Paolo Samorì
Here we describe the fabrication of organic phototransistors based on either single or multifibers integrated in three-terminal devices. These self-assembled fibers have been produced by solvent-induced precipitation of an air stable and solution-processable perylene di-imide derivative, i.e., PDIF-CN2. The optoelectronic properties of these devices were compared to devices incorporating more disordered spin-coated PDIF-CN2 thin-films. The single-fiber devices revealed significantly higher field-effect mobilities, compared to multifiber and thin-films, exceeding 2 cm2 V–1 s–1. Such an efficient charge transport is the result of strong intermolecular coupling between closely packed PDIF-CN2 molecules and of a low density of structural defects. The improved crystallinity allows efficient collection of photogenerated Frenkel excitons, which results in the highest reported responsivity (R) for single-fiber PDI-based phototransistors, and photosensitivity (P) exceeding 2 × 103 AW–1, and 5 × 103, respectively. These findings provide unambiguous evidence for the key role played by the high degree of order at the supramolecular level to leverage the material’s properties toward the fabrication of light-sensitive organic field-effect transistors combining a good operational stability, high responsivity and photosensitivity. Our results show also that the air-stability performances are superior in devices where highly crystalline supramolecularly engineered architectures serve as the active layer.

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