Organic,Bistable Devices with AgTCNQ Charge Transfer Complex by Vacuum Co-Deposition

The AgTCNQ thin-film was prepared by vacuum vapor co-deposition and characterized by infrared spectral analysis,and then a uniform AgTCNQ （TCNQ-- 7,7,8,8-tetracyanoquinodimethane） thin-film layer was sandwiched in a Ti/AgTCNQ/Ati crossbar structure array as organic bistable devices （OBD）.A reversible and reproducible memory switching property,caused by intermolecular charge transfer （CT） in the AgTCNQ thin-film, was observed in the organic bista- ble devices. The positive threshold voltage from the high impedance state to the low impedance was about 3.8-5V, with the reverse phenomenon occurring at a negative voltage of - 3.5- - 4. 4V,lower than that with a CuTCNQ active layer. The crossbar array of OBDs with AgTCNQ is promising for nonvolatile organic memory applications.

Inorganic and Organic Solution-Processed Thin Film Devices

Thin films and thin film devices have a ubiquitous presence in numerous conventional and emerging technologies. This is because of the recent advances in nanotechnology, the development of functional and smart materials,conducting polymers, molecular semiconductors, carbon nanotubes, and graphene, and the employment of unique properties of thin films and ultrathin films, such as high surface area, controlled nanostructure for effective charge transfer, and special physical and chemical properties, to develop new thin film devices. This paper is therefore intended to provide a concise critical review and research directions on most thin film devices, including thin film transistors, data storage memory, solar cells, organic light-emitting diodes, thermoelectric devices, smart materials, sensors, and actuators. The thin film devices may consist of organic, inorganic, and composite thin layers, and share similar functionality, properties, and fabrication routes. Therefore, due to the multidisciplinary nature of thin film devices, knowledge and advances already made in one area may be applicable to other similar areas. Owing to the importance of developing low-cost, scalable, and vacuum-free fabrication routes, this paper focuses on thin film devices that may be processed and deposited from solution.

Advances in Soft Materials for Sustainable Electronics

In the current shift from conventional fossil-fuel-based materials to renewable energy,ecofriendly materials have attracted extensive research interest due to their sustainability and biodegradable properties.The integration of sustainable materials in electronics provides industrial benefits from wasted bio-origin resources and preserves the environment.This review covers the use of sustainable materials as components in organic electronics,such as substrates,insulators,semiconductors,and conductors.We hope this review will stimulate interest in the potential and practical applications of sustainable materials for green and sustainable industry.

Rational Design of Star-shaped Molecules with Benzene Core and Naphthalimide Derivatives End Groups as Organic Light-emitting Materials

A series of star-shaped molecules with benzene core and naphthalimides derivatives end groups have been designed to explore their optical,electronic,and charge transport properties as charge transport and/or luminescent materials for organic light-emitting diodes（OLEDs）. The frontier molecular orbitals（FMOs） analysis has turned out that the vertical electronic transitions of absorption and emission are characterized as intramolecular charge transfer（ICT）. The calculated results show that the optical and electronic properties of star-shaped molecules are affected by the substituent groups in N-position of 1,8-naphthalimide ring. Our results suggest that star-shaped molecules with n-butyl（1）,benzene（2）,thiophene（3）,thiophene S？,S？-dioxide（4）,benzo[c][1,2,5]thiadiazole（5）,and 2,7a-dihydrobenzo[d]thiazole（6） fragments are expected to be promising candidates for luminescent and electron transport materials for OLEDs. This study should be helpful in further theoretical investigations on such kind of systems and also to the experimental study for charge transport and/or luminescent materials for OLEDs.

Fabrication of InAlGaN/GaN High Electron Mobility Transistors on Sapphire Substrates by Pulsed Metal Organic Chemical Vapor Deposition

Nearly lattice-matched InAIGaN/GaN heterostructure is grown on sapphire substrates by pulsed metal organic chemical vapor deposition and excellent high electron mobility transistors are fabricated on this heterostructure. The electron mobility is 1668.08cm2/V.s together with a high two-dimensional-electron-gas density of 1.43 × 10^13 cm-2 for the InAlCaN/CaN heterostructure of 2Onto InAlCaN quaternary barrier. High electron mobility transistors with gate dimensions of 1 × 50 μm2 and 4μm source-drain distance exhibit the maximum drain current of 763.91 mA/mm, the maximum extrinsic transconductance of 163.13 mS/mm, and current gain and maximum oscillation cutoff frequencies of 11 GHz and 21 GHz, respectively.

N-Aryl diketopyrrolopyrrole derivatives towards organic optical and electronic materials

Diketopyrrolopyrrole(DPP)and related derivatives have drawn great attention due to their applications in organic optical/electronic materials.Progress in these materials is associated with developments in the syntheses of the DPP family.Chemical modification of DPP at nitrogen atom,including N-alkylation and N-arylation,is an effective strategy to improve its physical and chemical properties,such as solubility,optical and semiconducting properties.However,N-arylation of DPPs remains challenging compared to the easily accessible N-alkylation.Herein,the synthesis of N-aryl DPP derivatives and correlatedπ-expanded DPPs are summarized,and their optical/electronic properties are introduced.The future perspectives of N-aryl DPP derivatives are also discussed.

Highly efficient through-space charge transfer TADF molecule employed in TADF-and TADF-sensitized organic light-emitting diodes

The inception and harnessing of excitons are paramount for the electroluminescence performance of organic light-emitting devices(OLEDs).Through-space charge transfer(TSCT)via intramolecular interaction has proved to be one of the most potent techniques employed to achieve 100% internal quantum efficiency.However,molecular strategies utilized to comprehensively enhance the electroluminescent performance of TSCT emitters regarding improving the photoluminescence quantum yield(PLQY)and elevating the light out-coupling efficiency remain arduous.To surmount this challenge,we deliberately designed and synthesized a proof-of-concept TSCT emitter called CzO-TRZ by incorporating an extra carbazole donor into spiroheterocyclic architecture.The introduction of rigid spiral fragments can immensely boost the horizontal orientation dipole ratio and establish an extra through-bond charge transfer(TBCT)radiative decay channel.As a result,a very high PLQY of 98.7%,fast kRISCof 2.2×10^(5)s^(-1)and high k_(r)^(s) of 2.2×10^(7)s^(-1),and an ultrahigh horizontal dipolar ratio of 90%were concurrently achieved for Cz O-TRZ blended films.Furthermore,corresponding thermally activated delayed fluorescence(TADF)-and TADF-sensitized fluorescence(TSF)-OLEDs based on CzO-TRZ demonstrated external quantum efficiencies(EQEs)of 33.4% and 30.3%,respectively,highlighting its versatile applications as both an emitter and sensitized host.

Purely organic optoelectronic materials with ultralong-lived excited states under ambient conditions

The exponential growth of utilizing synthetic organic molecules in optoelectronic applications poses strong demands for rational control over the excited states of the materials. The manipulation of excited states through molecular design has led to the development of high-performance optoelectronic devices with tunable emission colors, high quantum efficiencies and efficient energy/charge transfer processes. Recently, a significant breakthrough in lifetime tuning of excited states has been made;the purely organic molecules were found to have ultralonglived excited state under ambient conditions with luminescence lifetimes up to 1.35 s, which are several orders of magnitude longer than those of conventional organic fluorophores. Given the conceptual advance in understanding the fundamental behavior of excited state tuning in organic luminescent materials, the investigations of organic ultralong room-temperature phosphorescence(OURTP) should provide new directions for researches and have profound impacts on many different disciplines. Here, we summarized the recent understandings on the excited state tuning, the reported OURTP molecules and their design considerations,the spectacular photophysical performance, and the amazing optoelectronic applications of the newly emerged organic optoelectronic materials that free of heavy metals.

Recent advances of dithienobenzodithiophene-based organic semiconductors for organic electronics

In recent years, fused aromatic dithienobenzodithiophene(DTBDT)-based functional semiconductors have been potential candidates for organic electronics. Due to the favorable features of excellent planarity, strong crystallinity, high mobility, and so on, DTBDT-based semiconductors have demonstrated remarkable performance in organic electronic devices, such as organic feld-effect transistor(OFET), organic photovoltaic(OPV), organic photodetectors(OPDs). Driven by this success, recent developments in the area of DTBDT-based semiconductors for applications in electronic devices are reviewed, focusing on OFET, OPV, perovskite solar cells(PSCs), and other organic electronic devices with a discussion of the relationship between molecular structure and device performance. Finally, the remaining challenges, and the key research direction in the near future are proposed, which provide a useful guidance for the design of DTBDT-based materials.

Long-range ordering of composites for organic electronics:TIPS-pentacene single crystals with incorporated nano-fibers

Multi-component active materials are widely used for organic electronic devices, with every component contributing complementary and synergistic optoelectronic functions. Mixing these components generally leads to lowered crystallinity and weakened charge transport. Therefore, preparing the active materials without substantially disrupting the crystalline lattice is highly desired. Here, we show that crystallization of TIPS-pentacene from solutions in the presence of fluorescent nanofibers of a perylene bisimide derivative （PBI） leads to formation of composites with nanoflber guest incorporated in the crystal host. In spite of the binary composite structure, the TIPS-pentacene maintains the single- crystalline nature. As a result, the incorporation of the PB1 guest introduces additional fluorescence function but does not significantly reduce the charge transport property of the TIPS-pentacene host, exhibiting field-effect mobility as high as 3.34 cm^2 V^-1 s^-1 even though 26.4% of the channel area is taken over by the guest. As such, this work provides a facile approach toward high-performance multifunctional organic electronic materials.

Virtual special issue:Organic and polymer materials for electronics

Welcome to this virtual special issue focusing on organic and polymer materials for electronics published in Chinese Chemical Letters since 2017. For more than a century, people have always believed that organic compounds cannot be well employed for electronic conducting. Till 2000,Heeger,MacDiarmid and Shirakawa were acknowledged by the Nobel Prize of chemistry for

High-performance and multifunctional organic field-effect transistors

Organic field-effect transistors(OFETs)refer to field-effect transistors that use organic semiconductors as channel materials.Owing to the advantages of organic materials such as solution processability and intrinsic flexibility,OFETs are expected to be applicable in emergent technologies including wearable electronics and sensors,flexible displays,internet-of-things,neuromorphic computing,etc.Improving the electrical performance and developing multifunctionalities of OFETs are two major and closely relevant aspects for OFETs-related research.The former one aims for investigating the device physics and expanding the horizons of OFETs,while the later one is critical for leading OFETs into practical and emergent applications.The development in each of the two aspects would undoubtfully promote the other and bring more confidence for future development of OFETs.Hence,this review is divided into two parts that respectively summarize the recent progress in high-performance OFETs and multifunctional OFETs.

Customizable 2D Covalent Organic Frameworks for Optoelec-tronic Applications

2D covalent organic framework(2D-COF),a modular three-dimensional material,is easily influenced by the component module.The assembly of different functionalized modules gives 2D-COF unique performance.The modular structure not only allows for customi-zation but also allows for variety,which gives 2D-COF a wide range of functions.Hence,many building blocks with catalytic,ligand,semiconductor,luminescent,and redox centers are integrated into the COF scaffold.The connection and assembly of such modules determine the nature of the final block material.The intra-layer connections of the modules form a monolayer mesh chemical structure,and the subsequent stacking of the monolayer mesh structure produces the final crystalline porous material-2D-COF.This review describes in detail the potential of COF materials as optoelectronic materials and our understanding of optoelectronic processes,starting from monolayer reticulation chemistry to final 3D stacked structures,thus establishing a new paradigm for the ra-tional design of well-defined novel 2D-COF optoelectronic materials and devices.

1,2,5,6-Naphthalene Diimides:A Class of Promising Building Blocks for Organic Semiconductors

Organic semiconductors have drawn extensive atten-tion due to their optoelectronic properties and wide applications in organic optoelectronics.In comparison with the popular 1,4,5,8-naphthalene diimides(1,4,5,8-NDIs),the angular-shaped 1,2,5,6-NDIs have exhibited tunable photophysical properties,self-as-sembly behaviors and charge transporting properties.Due to these unique features,1,2,5,6-NDIs show great potential for construction of high performance n-func-tional materials.In this review,we highlight the recent advances and future prospects of 1,2,5,6-NDI-basedπ-systems in the field of organic optoelectronics,in-cluding molecular design,synthesis,structure-prop-erty relationships as well as the applications in high performance organic field-effect transistors,organic photovoltaics,perovskite solar cells,and so on.

Organic single-crystal light-emitting transistors with external quantum efficiency over 20%

Organic light-emitting transistors(OLETs)have attracted increasing attention because of their potential applications in next-generation displays and high-energy operating devices.However,the simultaneous achievement of high luminescent efficiency and carrier mobility in organic semiconductors remains challenging because the localized excitons are advantageous for light emission,whereas the delocalized carriers are beneficial for efficient charge migration.Herein,we report an organic single crystal of a cyano-substituted styrene derivative with balanced mobility yielding a record-high external quantum efficiency of 20.5%in OLETs.Temperature-dependent I–V curves and electronic structure analyses based on firstprinciples calculations were performed to disclose the underlying mechanism as a band transport,which provides an efficient way to achieve high quantum efficiency in OLETs.

Thermoelectric Properties of an Indandione-Terminated Quinoidal Compound:Effect of the n-Type Dopants

The investigation of n-type doping holds a significant interest for the application of thermoelectrics.Herein,the doping of an indandione-terminated compound Q-4F with a singlet open-shell ground state was studied using two n-dopants N-DMBI and LCV.Both of these two dopants can effectively dope Q-4F due to the large offset between the singly occupied molecular orbital(SOMO)of dopants and the lowest unoccupied molecular orbital(LUMO)of Q-4F.N-DMBI has a higher doping ability than LCV as demonstrated by the UV-vis-NIR and EPR measurements.However,in comparison to N-DMBI doped Q-4F,LCV doped system exhibits much higher electrical conductivity and power factor due to its unperturbed molecular packing and favorable morphology after doping.The optimal conductivity of LCV doped Q-4F is 7.16×10^(-2)±0.16 S·cm^(-1) and the highest power factor reaches 12.3±0.85μW·m–1·K^(-2).These results demonstrate that the modulation of n-dopants is a powerful strategy to balance the doping efficiency and microstructure toward a maximum thermoelectric performance.

High mobility organic semiconductors for field-effect transistors

Organic field-effect transistors(OFETs) are attracting more and more attention due to their potential applications in low-cost, large-area and flexible electronic products. Organic semiconductors(OSCs) are the key components of OFETs and basically determine the device performance. The past five years have witnessed great progress of OSCs. OSCs used for OFETs have made rapid progress, with field-effect mobility much larger than that of amorphous silicon(0.5?1.0 cm2/(V s)) and of up to 10 cm2/(V s) or even higher. In this review, we demonstrate the latest progress of OSCs for OFETs, where more than 50 representative OSCs are highlighted and analyzed to give some valuable insights for this important but challenging field.

Recent advances in organic-based materials for resistive memory applications

With the rapid development of data-driven human interaction,advanced datastorage technologies with lower power consumption,larger storage capacity,faster switching speed,and higher integration density have become the goals of future memory electronics.Nevertheless,the physical limitations of conventional Si-based binary storage systems lag far behind the ultrahigh-density requirements of post-Moore information storage.In this regard,the pursuit of alternatives and/or supplements to the existing storage technology has come to the forefront.Recently,organic-based resistive memory materials have emerged as promising candidates for next-generation information storage applications,which provide new possibilities of realizing high-performance organic electronics.Herein,the memory device structure,switching types,mechanisms,and recent advances in organic resistive memory materials are reviewed.In particular,their potential of fulfilling multilevel storage is summarized.Besides,the present challenges and future prospects confronted by organic resistive memory materials and devices are discussed.

Alignment and patterning of organic single crystals for field-effect transistors

Organic field-effect transistors are of great importance to electronic devices.With the emergence of various preparation techniques for organic semiconductor materials,the device performance has been improved remarkably.Among all of the organic materials,single crystals are potentially promising for high performances due to high purity and well-ordered molecular arrangement.Based on organic single crystals,alignment and patterning techniques are essential for practical industrial application of electronic devices.In this review,recently developed methods for crystal alignment and patterning are described.

Appending triphenyltriazine to 1,10-phenanthroline: a robust electron-transport material for stable organic light-emitting diodes

There has been an increasing demand for high-performance and cost-effective organic electron-transport materials for organic light-emitting diodes （OLEDs）. In this contribution, we present a simple compound 3-（3-（4,6-diphenyl-l,3,5-triazin-2-yl）phenyl）-1,10-phenanthroline through the facile Pd-catalyzed coupling of a triphenyltriazine boronic ester with 3-hromo-1,10-phenanthroline. It shows a high Tg of 112℃. The ultraviolet photoelectron spectroscopy measurements reveal a deep HOMO level of -6.5 eV. The LUMO level is derived as -3.0 eV, based on the optical bandgap. The low-temperature solid-state phosphorescent spectrum gives a triplet energy of -2.36eV. n-Doping with 8-hydroxyquinolatolithium （Liq, 1：1） leads to considerably improved electron mobility of 5.2 × 10 -6 -5.8 × 10 -5 cm2 v-1 S-1 at E=（2-5） × 10 5Vcm -1, in contrast with the triarylphosphine oxide- phenantroline molecular conjugate we reported previously. It has been shown that through optimizing the device structure and hence suppressing polaron-exciton annihilation, introducing this single Liq-doped electron-transport layer could offer high-efficiency and stable phosphorescent OLEDs.