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

Abstract

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 cm(2) 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 × 10(3) AW(-1), and 5 × 10(3), 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.

Ultrathin Air-Stable n-Type Organic Phototransistor Array for Conformal Optoelectronics

“…According to previous reports and our results [Fig. S1], we attribute the good device stability to the molecular design of PTCDI–C 13 H 27 and hydrophobic nature for the decreased trap density in PMMA dielectric 22,31 . These properties can offer the basic for further study on photoelectric properties.

Figure 2Electrical properties of the PTCDI-C 13 H 27 thin-film transistor: ( a , b ) Typical transfer and output curves of the device.

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On the Working Mechanisms of Solid‐State Double‐Layer‐Dielectric‐Based Organic Field‐Effect Transistors and Their Implication for Sensors

“…Photoresponsivity is a device parameter typically defined as the photoresponse divided by the incident laser intensity on the transistor channel (Photoresponsivity = Photoresponse/ (P*WL)). For the blue laser diode values of 3.7 × 10 6 (%W −1 ) and 1 × 10 6 (%W −1 ), in the OFF V G = 0.2 V and ON-state at V G = −0.2 V, respectively, were measured and are lower than reported literature values, [45] but it is the first time that tunable photoresponse of a polymer field-effect transistor has been reported for bias voltages lower than 1 V.…”

“…[45] The fast response upon illumination suggests photogenerated charge carriers inside the semiconductor rather than slower thermal processes and has been observed in other organic semiconductors. [42,46] While driving the FET at different gate bias voltages, two operation regions can be identified.…”

Performance improvement of organic phototransistors by using polystyrene microspheres

“…More importantly, some OSCs with suitable optical band-gaps can be fabricated into phototransistors for light detection ranging from ultraviolet (UV) to near infrared (NIR). It is therefore essential to study OSCbased phototransistors [2,[18][19][20][21][22][23]. Developing the OSCs films with nano/micro-structures has attracted interest over the recent years, which is effective to improve the performances of the OPTs [24,25].…”