Development of conformal n-channel organic phototransistor (OPT) array is urgent for future applications of organic complementary circuits in portable and wearable electronics and optoelectronics. In this work, the ultrathin conformal OPT array based on air-stable n-type PTCDI-C13H27 was fabricated. The OPT array shows excellent electrical and photoelectrical performance, good device uniformity, and remains stable in electron mobility by 83% after 90 days compared to the initial values. Eventhough mobility, on-state current, off-state current, and photocurrent of PTCDI-C13H27 thin film phototransistor show slight decrease with the decreased bending radius, the device still remains the stable photosensitivity as high as 104 when the device is freely adhered on the 2D surfaces and 3D hemispherical sphere, which is in a class with the highest photosensitivity for perylene diimide derivatives. These results present the promising application potential of our conformable air-stable n-type PTCDI-C13H27 OPTs as the photodetection system of curved artificial compound eyes in wearable and portable electronics and optoelectronics.

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

Organic semiconductors have attracted a lot of attention since the discovery of highly doped conductive polymers, due to the potential application in field-effect transistors (OFETs), light-emitting diodes (OLEDs) and photovoltaic cells (OPVs). Single crystals of organic semiconductors are particularly intriguing because they are free of grain boundaries and have long-range periodic order as well as minimal traps and defects. Hence, organic semiconductor crystals provide a powerful tool for revealing the intrinsic properties, examining the structure–property relationships, demonstrating the important factors for high performance devices and uncovering fundamental physics in organic semiconductors. This review provides a comprehensive overview of the molecular packing, morphology and charge transport features of organic semiconductor crystals, the control of crystallization for achieving high quality crystals and the device physics in the three main applications. We hope that this comprehensive summary can give a clear picture of the state-of-art status and guide future work in this area.

Organic semiconductor crystals

Functional organic field-effect transistors (OFETs) have attracted increasing attention in the past few years due to their wide variety of potential applications. Research on functional OFETs underpins future advances in organic electronics. In this review, different types of functional OFETs including organic phototransistors, organic memory FETs, organic light emitting FETs, sensors based on OFETs and other functional OFETs are introduced. In order to provide a comprehensive overview of this field, the history, current status of research, main challenges and prospects for functional OFETs are all discussed.

Functional organic field-effect transistors.

Organic molecules and semiconductors have been proposed as active part of a large variety of nonvolatile memory devices, including resistors, diodes and transistors. In this review, we focus on electrically reprogrammable nonvolatile memories. We classify several possible devices according to their operation principle and critically review the role of the π-conjugated materials in the device operation. We propose specifications for applications for organic nonvolatile memory and review the state of the art with respect to these target specifications. Conclusions are drawn regarding further work on materials and device architectures.

Polymer and Organic Nonvolatile Memory Devices

Naphthalene and perylene diimides for organic transistors

Multibit Storage of Organic Thin‐Film Field‐Effect Transistors

[*] Prof. Y. Q. Liu, Y. G. Wen, Dr. C. A. Di, Dr. Y. Wang, Dr. X. N. Sun, Y. L. Guo, J. Zheng, W. P. Wu, S. H. Ye, Prof. G. Yu Beijing National Laboratory for Molecular Sciences Key Laboratory of Organic Solids Institute of Chemistry Chinese Academy of Sciences Beijing 100190 (P.R. China) E-mail: liuyq@iccas.ac.cn Y. G. Wen, X. N. Sun, Y. L. Guo, J. Zheng, W. P. Wu, S. H. Ye Graduate School of Chinese Academy of Sciences Beijing 100039 (P.R. China)

Improvements in Stability and Performance of N, N′-Dialkyl Perylene Diimide-Based n-Type Thin-Film Transistors

We report stable organic field-effect transistors (OFETs) based on pentacene. It was found that device stability strongly depends on the dielectric layer. Pentacene thin-film transistors based on the bare or polystyrene-modified SiO2 gate dielectrics exhibit excellent electrical stabilities. In contrast, the devices with the octadecyltrichlorosilane (OTS)-treated SiO2 dielectric layer showed the worst stabilities. The effects of the different dielectrics on the device stabilities were investigated. We found that the surface energy of the gate dielectric plays a crucial role in determining the stability of the pentacene thin film, device performance and degradation of electrical properties. Pentacene aggregation, phase transfer and film morphology are also important factors that influence the device stability of pentacene devices. As a result of the surface energy mismatch between the dielectric layer and organic semiconductor, the electronic performance was degraded. Moreover, when pentacene was deposited on the OTS-treated SiO2 dielectric layer with very low surface energy, pentacene aggregation occurred and resulted in a dramatic decrease of device performance. These results demonstrated that the stable OFETs could be obtained by using pentacene as a semiconductor layer.

Effect of dielectric layers on device stability of pentacene-based field-effect transistors

Two asymmetrically substituted dicyanovinyl heterotetracenes are synthesized and characterized. Single-crystal X-ray diffractions indicate both intermolecular hydrogen bonds and π-stacking existing in the solid-state structures. The solvatochromic behaviors of the two heterotetracenes were investigated in a variety of solvents. Both experimental and computational results suggest that the two heterotetracenes have low-lying lowest unoccupied molecular orbitals and thus may be potential n-type or bipolar organic semiconductors for organic electronics.

Dicyanovinyl heterotetracenes: synthesis, solid-state structures, and photophysical properties.

Asymmetrical heteroacene up to six fused rings, tetraceno[2,3-b]benzo[d]thiophene (TBT), was synthesized facilely and its physicochemical properties and device applications were investigated. Field-effect transistors (FETs) fabricated with TBT as semiconducting layers showed carrier mobility up to 0.13 cm2 V−1 s−1. The transistors also exhibited a photoeffect and a ratio of photocurrent to dark-current as high as 104 was achieved. Density functional theory and FET results demonstrated that, for bent heteroacenes, increasing a benzene ring in conjugation length would not result in higher field-effect mobility, and the FET performance is more influenced by the thin film morphology. All these results suggest that the introduction of heteroatoms provides an efficient route for exploring the chemistry of larger acenes.

Jian Zheng

Papers

Multibit Storage of Organic Thin‐Film Field‐Effect Transistors

Improvements in Stability and Performance of N, N′-Dialkyl Perylene Diimide-Based n-Type Thin-Film Transistors

Effect of dielectric layers on device stability of pentacene-based field-effect transistors

Dicyanovinyl heterotetracenes: synthesis, solid-state structures, and photophysical properties.

Design, Synthesis, and Properties of Asymmetrical Heteroacene and Its Application in Organic Electronics