Advanced electronic materials | 2021
Luminescence Behavior and Acceptor Effects of Ambipolar Polymeric Electret on Photorecoverable Organic Field‐Effect Transistor Memory
Abstract
The 5G communication and artificial intelligence systems have gained considerable interest in the features of high transmission speed, energy-saving, low latency, and low interference. The functionalities of applied devices have been explored widely such as light-emitting electronics, image sensors, and nonvolatile flash memories.[1] In the plethora of opticalcommunicated devices, the flash photomemory based on the configuration of field-effect transistors (FET) has attracted attention especially since it possesses high compatibility to complementary metal-oxide-semiconductor circuits.[2] Furthermore, the photo memory also serves as an indispensable basic building segment of computation technology in modern bigdata storage devices. On the other hand, the large magnitudes of conventional electrical stresses could be potentially abandoned in the process of programming or erasing operation; therefore, photoassisted FET memory, able to utilize photoexcited carriers to modulate the status of electrical signals, becomes an extremely remarkable feature.[3] Currently, photoassisted FET memory devices are successfully constructed by exploiting nanofloating gate dielectrics[4] and polymer-based electret layers[5] in typical FET devices. Utilizing polymer-based electret for organic field-effect transistor (OFET) photomemory inheres multiple advantages, including the charge storage layer could be easily prepared by solution-process and the designed chemical skeleton dominates the emerged number of excitons and the relaxation pathways of excitons for memory characteristic.[2b–e,6] Recently, OFET-type optical memories with conjugated donor–acceptor electret have been demonstrated that the photorecovery behavior is related to the recombination of stored charges with photogenerated excitons.[5b,7] However, the role between the electret and organic semiconductor layer in the photoinduced recovery mechanism has not been comprehended soundly.[3c,8] As a result, systematically designed conjugated-based polymer electret with widely divergent exciton-dissipation routes, such as aggregationinduced emission (AIE)[9] and aggregation-caused quenching Photorecovery systems are considered to be a potential technology in photosensor, green energy-saving, and high-speed communication applications (light-fidelity). However, the role of photoactive-electret and semiconductor in the photorecovery system is still unintelligible. Herein, triphenylamine (TPA)-based donor–acceptor polymers are designed as electrets with more effective excitons dissociation for organic field-effect transistor memory equipped with photosensitive and photorecoverable response. By modifying TPA-derived conjugated polymers with various electron-withdrawing groups (PTPA-CN, PTPA-CNBr, and PTPA-3CN), the obtained PTPAs induce disparate luminescent behaviors in the aggregated state. PTPA-CN and PTPA-CNBr exhibit aggregation-induced emission (AIE) featuring the energy dissipation of partial photoexcited excitons through radiation, while PTPA-3CN turns to aggregation-caused quenching (ACQ) behavior leading considerable number of nonemissive excitons which can directly recombine with charged medium, an electret containing trapped charges. Pentacene-based transistor devices incorporated with studied photoactive electrets are constructed for mechanism investigation. The results demonstrate that photorecovery response ability of ACQ-polymer displays much faster than that of AIE-polymers, PTPA-CN, and PTPA-CNBr, upon UV light irradiation, attributing to the intensely electron-withdrawing ability of acceptor attached on the conjugated skeleton. The ACQ-electret device behaves superior memory switching performance with reliable endurance characteristics under the cycling stress of electrical-programming and optical-erasing operations, demonstrating the feasibility for organic optoelectronic applications.