Organic thin film transistors (OTFTs) are a promising technology for the application of photosensors in smart wearable devices. Light-induced electrical behavior of OTFTs is explored to achieve diverse functional requirements. In most studies, OTFTs show an increased drain current (I_D) under light irradiation. Here, we use an ultraviolet (UV) light absorption top layer, tris(8-hydroxyquinoline) aluminum (Alq3), to improve the UV light response of poly(3-hexylthiophene-2,5-diyl) (P3HT)-based OTFTs. Unexpectedly, the Alq3-covered device operated at the accumulation mode demonstrates a decreased I_D during the UV light irradiation. N,N′-Ditridecyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI, electron acceptor), pentacene (electron donor), and lithium fluoride (LiF, insulator) as an interlayer were inserted between the P3HT and the Alq3 layers. The PTCDI/Alq3-covered device also shows an unusual decrease in I_D under the UV light but an increase in I_D under the green light. The pentacene/Alq3-covered device shows an increased I_D during the UV light irradiation and, unexpectedly, a memory effect in I_D after removing the UV light. The LiF/Alq3-covered device exhibits an electrical behavior similar to the bare P3HT-based device under the UV light. Results of spectroscopic analyses and theoretical calculations have shown that the occurrence of charge transfer at heterojunctions during the UV light irradiation causes charge modulation in the multilayered P3HT-based OTFTs and then results in an unusual decrease or memory effect in I_D. In addition, the unexpected I_D reduction can be observed in the Alq3-covered poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene]-based OTFTs under UV light. The features, including opposite electrical responses to different wavelengths of light and optical memory effect, provide the multilayered P3HT-based OTFTs with potential for various optical applications, such as image recognition devices, optical logic gates, light dosimeters, and optical synapses.

中文翻译：

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用于多功能有机薄膜晶体管的紫外光激活电荷调制异质结

有机薄膜晶体管（OTFT）是光电传感器在智能可穿戴设备中应用的一项有前途的技术。探索 OTFT 的光诱导电行为以实现不同的功能要求。在大多数研究中，OTFT中显示出增加的漏电流（我_d光照射下）。在这里，我们使用紫外 (UV) 光吸收顶层三（8-羟基喹啉）铝（Alq3）来改善基于聚（3-己基噻吩-2,5-二基）（P3HT）的 OTFT 的紫外光响应. 出乎意料的是，在累积模式下运行的 Alq3 覆盖的器件在紫外光照射期间表现出降低的I _D。ñ，ñ'-Ditridecyl-3,4,9,10-苝四羧酸二酰亚胺（PTCDI，电子受体）、并五苯（电子供体）和氟化锂（LiF，绝缘体）作为中间层插入 P3HT 和 Alq3 层之间。PTCDI/Alq3 覆盖的器件在紫外光下也表现出异常的I _D下降，但在绿光下I _D增加。并五苯/Alq3 覆盖的器件在紫外线照射期间显示出增加的I _D，并且出乎意料地，在I _{D 中}出现了记忆效应去除紫外线后。LiF/Alq3 覆盖的器件在紫外光下表现出类似于基于 P3HT 的裸器件的电气行为。光谱分析和理论计算的结果表明，在紫外光照射期间异质结处发生的电荷转移会导致基于 P3HT 的多层 OTFT 中的电荷调制，然后导致I _D异常降低或记忆效应。此外，出乎意料的我_d减少所用的的Alq3覆盖的聚[2,5-双（3- tetradecylthiophen -2-基）噻吩并[3,2-观察b]噻吩]基OTFT在紫外光下。这些特性，包括对不同波长光的相反电响应和光学记忆效应，为基于 P3HT 的多层 OTFT 提供了各种光学应用的潜力，例如图像识别设备、光学逻辑门、光剂量计和光学突触。