Search query: Developing high mobility emissive organic semiconductors towards integrated optoelectronic devices

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abstract: The achievement of organic semiconductors with both high mobility and strong fluorescence emission remains a challenge. High mobility requires molecules which pack densely and periodically, while serious fluorescence quenching typically occurs when fluorescent materials begin to aggregate (aggregation induced quenching (AIQ) Indeed, classical materials with strong fluorescent emission always exhibit low mobility, for example, tris(8 hydroxyquinoline) aluminium (ALQ) and phenylenevinylene based polymers with mobility only 10 6 10 5 cm2V 1s 1, and benchmark organic semiconductors with high mobility demonstrate very weak emission, for example, rubrene exhibits a quantum yield<1% in crystalline state and pentacene shows very weak fluorescence in the solid state. However, organic semiconductors with high mobility and strong fluorescence are necessary for the achievement of high efficiency organic light emitting transistors (OLETs) and electrically pumped organic lasers. Therefore, it is necessary for developing high mobility emissive organic/polymeric semiconductors towards a fast mover for the organic optoelectronic integrated devices and circuits.
author_names: Huanli Dong

Wenping Hu

Alan J Heeger
title: Developing high mobility emissive organic semiconductors towards integrated optoelectronic devices (Conference Presentation)
venue: Organic Photonics Electronics
year: 2016

abstract: Simultaneously modulating the optical and electrical properties of organic semiconductors is crucial for advancing their desired applications in integrated optoelectronic devices. Here, we realize a goal of optimizing the light emission and field effect properties of an anthracene derivative, 1,4 di(anthracen 9 yl)buta 1,3 diyne (DABD) by tuning its crystal polymorphs. Two phase crystals, that is a phase rhombic sheet crystals and b phase ribbon shape crystals of DABD are controllably obtained. Compared with the a phase crystals, the b phase DABD crystals exhibit better integrated optoelectronic performances with charge carrier mobility of 0.25 cm2 V 1 s 1 and strong fluorescent emission. This work suggests that polymorph engineering would be a promising avenue to realize simultaneous modulation of the multifunctional properties of organic semiconductors towards appropriate applications in organic optoelectronics.
author_names: Dan Liu

Chenguang Li

Shujie Niu

Yang Li

Mengxiao Hu

Qingyuan Li

Wei-Gang Zhu

Xiaotao Zhang

Huanli Dong

Wenping Hu
title: A case study of tuning the crystal polymorphs of organic semiconductors towards simultaneously improved light emission and field effect properties
year: 2019

abstract: Solution processed n type organic semiconductor micro/nanocrystals (OSMCs) are fundamental elements for developing low cost, large area, and all organic logic/complementary circuits. However, the development of air stable, highly aligned n channel OSMC arrays for realizing high performance devices lags far behind their p channel counterparts. Herein, we present a simple one step slope coating method for the large scale, solution processed fabrication of highly aligned, air stable, n channel ribbon shaped single crystalline N,N' bis(2 phenylethyl) perylene 3,4:9,10 tetracarboxylic diimide (BPE PTCDI) arrays. The slope and patterned photoresist (PR) stripes on the substrate are found to be crucial for the formation of large area submicron ribbon arrays. The width and thickness of the BPE PTCDI submicron ribbons can be finely tuned by controlling the solution concentration as well as the slope angle. The resulting BPE PTCDI submicron ribbon arrays possess an optimum electron mobility up to 2.67 cm2*V 1*s 1 (with an average mobility of 1.13 cm2*V 1*s 1) which is remarkably higher than that of thin film counterparts and better than the performance reported previously for single crystalline BPE PTCDI based devices. Moreover, the devices exhibit robust air stability and remain stable after exposing in air over 50 days. Our study facilitates the development of air stable, n channel organic field effect transistors (OFETs) and paves the way towards the fabrication of high performance, organic single crystal based integrated circuits.
author_names: Liang Wang

Xiujuan Zhang

Gaole Dai

Wei Deng

Jiansheng Jie

Xiaohong Zhang
title: High mobility air stable n type field effect transistors based on large area solution processed organic single crystal arrays
venue: Nano Research
year: 2017

abstract: Organic crystals simultaneously displaying high carrier mobility and high luminescence efficiency are expected to be of interest for the fundamental research of light emitting devices, and may offer renewed hope for achieving electrical pumping of solid state organic lasers. However, high charge transport and efficient light emission have been mutually exclusive due to the different inherent natures of their aggregation states in single crystals. Here, we report the successful growth of a pentacene doped 1,4 bis(2 cyano styryl)benzene (2 CSBPc) crystal that showed a high carrier mobility of 0.51 cm2 V 1 s 1, efficient emission of red light with a quantum yield of up to 50% and a low amplified spontaneous emission (ASE) threshold of 46 kW cm 2 using a physical vapor transport (PVT) method. The achieved high carrier mobility was due to the retention of structural order after doping Pc molecules into the 2 CSB matrix, as well as being due to the extensive intermolecular p orbital overlap stacks in the crystal. The spectral matching between 2 CSB emission and Pc absorption promoted host guest energy transfer leading to the high luminescence efficiency, and meanwhile, the uniaxially oriented molecular arrangement had the benefit of producing ASE with a low energy threshold. The molecular electronic structures, reorganization energies and orbital overlap integrals were calculated to further elucidate the influences of Pc doping on the luminescence and charge transport characteristics. The primary results indicated that integrated multi functional optoelectronic crystals can be obtained via a doping strategy, which is of great significance for developing high performance organic laser materials and devices.
author_names: Yang Zhao

Liyan Wang

Chen Xi

Biao Zhang

Fangzhong Shen

Hua Song

Huan Wang
title: A high mobility, high luminescence and low threshold pentacene doped cyano substituted distyrylbenzene crystal
year: 2019

abstract: Organic photodetectors with UV sensitivity are of great potential for various optoelectronic applications. Integration of high charge carrier mobility, long exciton diffusion length as well as unique UV sensitivity for active materials is crucial for construction of UV sensitive devices with high performance, however, very few organic semiconductors can integrate these properties simultaneously. Herein, two novel organic semiconductors containing large steric hindrance triphenylamine groups, 1,6 distriphenylamineethynylpyrene (1,6 DTEP) and 2,7 distriphenylamineethynylpyrene (2,7 DTEP) are designed and synthesized. It demonstrates that the single crystals of both 1,6 DTEP and 2,7 DTEP exhibit superior integrated optoelectronic properties of high charge carrier mobility, unique UV absorption, high photoluminescence quantum yields as well as small exciton binding energies. Organic phototransistors constructed using 1,6 DTEP and 2,7 DTEP single crystals show ultrasensitive performance with ultra high photoresponsivity of 2.86 x 106 and 1.04 x 105 A W 1 detectivity (D* of above 1.49 x 1018 and 5.28 x 1016 Jones under 370 nm light illumination, respectively. It indicates the great potential of 1,6 DTEP and 2,7 DTEP based phototransistors for organic UV photodetector applications and also provides a new design strategy to develop series of better performance UV photoelectric organic materials for related research in organic optoelectronics.
author_names: Jingwei Tao

Dan Liu

Zhengsheng Qin

Bo Shao

Jiangbo Jing

Hongxiang Li

Huanli Dong

Bin Xu

Wenjing Tian
title: Organic UV Sensitive Phototransistors Based on Distriphenylamineethynylpyrene Derivatives with Ultra High Detectivity Approaching 1018.
venue: Advanced materials
year: 2020

abstract: While the field of perovskite based optoelectronics has mostly been dominated by photovoltaics, light emitting diodes and transistors, semiconducting properties peculiar to perovskites make them interesting candidates for innovative and disruptive applications in light signal detection. Perovskites combine effective light absorption in the broadband range with good photo generation yield and high charge carrier mobility, which combination provides promising potential for exploiting sensitive and fast photodetectors that are targeted for image sensing, optical communication, environmental monitoring, or chemical/biological detection. Currently, organic inorganic hybrid and all inorganic halide perovskites with controlled morphologies of polycrystalline thin films, nano particles/wires/sheets, and bulk single crystals have shown key figure of merit features in terms of their responsivity, detectivity, noise equivalent power, linear dynamic range, and response speed. The sensing region has been covered from ultraviolet visible near infrared (UV Vis NIR) to gamma photons, based on two or three terminal device architectures. Diverse photoactive materials and devices with superior optoelectronic performances have stimulated attention from researchers in multidisciplinary areas. We offer a comprehensive overview of the recent progress of perovskite based photodetectors, focusing on versatile compositions, structures, and morphologies of constituent materials, and diverse device architectures toward the superior performance metrics. Combining the advantages of both organic semiconductors (facile solution processability) and inorganic semiconductors (high charge carrier mobility) perovskites are expected to replace commercial silicon for future photodetection applications. The optical and electronic properties of noble metallic nanoparticles can be exploited to enhance the performance of inorganic/organic photodetectors. We integrated a uniformly distributed layer of Au nanorods (AuNRs) into vertically structured perovskite photoconductive photodetectors and report, as a result, perovskite AuNR hybrid photodetectors that exhibit significant photocurrent enhancements. Ultimately it achieves a responsivity of ~320 A/W at a low driving voltage of 1 V. This is an improvement of 60% compared to the responsivity of pristine devices ~200 A/W) The high responsivity and low driving voltage place this device among the highest performing perovskite based thin film photoconductive photodetectors reported. We characterized the stability and linearity of the photoresponse following repeated light/dark cycles. The hybrid device also shows a fast response (with the decay time of ~95 ns) compared to pristine devices ~230 ns) The improvements in photodetection performance are attributed to plasmon enhanced optical absorption, as well as advances in charge extraction and transport. Metal halide perovskites have rapidly advanced thin film photovoltaic performance; as a result, the materials' ob served instabilities urgently require a solution. Using density functional theory (DFT) we show that a low energy of formation, exacerbated in the presence of humidity, explains the propensity of perovskites to decompose back into their precursors. We find, also using DFT, that intercalation of phenylethylammonium between perovskite layers in troduces quantitatively appreciable van der Waals interactions; and these drive an increased formation energy and should therefore improve material stability. Here we report the reduced dimensionality (quasi 2D) perovskite films that exhibit improved stability while retaining the high performance of conventional three dimensional perovskites. Continuous tuning of the dimensionality, as assessed using photophysical studies, is achieved by the choice of stoi chiometry in materials synthesis. We achieve the first certified hysteresis free solar power conversion in a planar per ovskite solar cell, obtaining a 15.3% certified PCE, and observe greatly improved performance longevity. The same protocol was applied to develop highly stable and efficient photodectors in diverse device configurations. Organometal halide perovskites exhibit large bulk crystal domain sizes, rare traps, excellent mobilities, and carriers that are free at room temperature properties that support their excellent performance in charge separating devices. In devices that rely on the forward injection of electrons and holes, such as light emitting diodes (LEDs) excellent mobilities contribute to the efficient capture of nonequilibrium charge carriers to rare nonradiative centres. Moreover, the lack of bound excitons weakens the competition of desired radiative over undesired nonradiative recombination. Here we also report a perovskite mixed material, one comprised of a series of differently quantum size tuned grains, that funnels photoexcitations to the lowest bandgap light emitter in the mixture. The materials function as charge carrier concentrators, ensuring that radiative recombination successfully outcompetes trapping and hence nonradiative recombination. We use the new material to build devices that exhibit an external quantum efficiency (EQE) of 8.8% and a radiance of 80 Wsr 1m 2. These represent the brightest and most efficient solution processed near infrared LEDs to date. Here we show that, by concentrating photoexcited states into a small subpopulation of radiative domains, one can achieve a high quantum yield even at low excitation intensities. We tailor the composition of quasi 2D perovskites to direct the energy transfer into the lowest bandgap minority phase, and to do so faster than it is lost to non radiative centres. The new material exhibits 60% photoluminescence quantum yield at excitation intensities as low as 1.8 mW/cm2, yielding a ratio of quantum yield to excitation intensity of 0.3 cm2/mW; this represents a two orders of magnitude decrease in the excitation power required to reach high efficiency compared to the best prior reports. Using this strategy, we report LEDs with EQEs of 7.4% and a high luminescence of 8400 cd/m2.
author_names: Dong Ha Kim

Huan Mei Wang

Ju Won Lim

Li Na Quan

Ilgeum Lee

Edward H Sargent
title: Optoelectronic hybrid perovskite materials and devices (Conference Presentation)
year: 2018

abstract: Organic light emitting transistors (OLETs) integrate the functions of light emitting diodes and field effect transistors into a unique device, opening a new door for optoelectronics. However, there is still a challenge due to the absence of high quality organic semiconductors for OLETs. Herein, we reported a novel molecule 2,6 di(anthracen 2 yl)naphthalene (2,6 DAN) which exhibited mobility of up to 19 cm 2 *V 1 *s 1 and an absolute fluorescence quantum yield of 37.09% which are good values for organic semiconductors. Moreover, OLETs based on 2,6 DAN single crystals showed bright yellowish green emission and well balanced ambipolar charge transport. The excellent ratio of hole to electron mobility can reach up to 0.86, which is superior to most single component OLETs in typical device configurations reported so far.
author_names: Lei Zheng

Jinfeng Li

Ke Zhou

Xixia Yu

Xiaotao Zhang

Huanli Dong

Wenping Hu
title: Molecular scale integrated multi functions for organic light emitting transistors
venue: Nano Research
year: 2020

abstract: Organic semiconducting single crystals (OSSCs) are ideal candidates for the construction of high performance optoelectronic devices/circuits and a great platform for fundamental research due to their long range order, absence of grain boundaries, and extremely low defect density. Impressive improvements have recently been made in organic optoelectronics: the charge carrier mobility is now over 10 cm2 V 1 s 1 and the fluorescence efficiency reaches 90% for many OSSCs. Moreover, high mobility and strong emission can be integrated into a single OSSC, for example, showing a mobility of up to 34 cm2 V 1 s 1 and a photoluminescence yield of 41.2% These achievements are attributed to the rational design and synthesis of organic semiconductors as well as improvements in preparation technology for crystals, which accelerate the application of OSSCs in devices and circuits, such as organic field effect transistors, organic photodetectors, organic photovoltaics, organic light emitting diodes, organic light emitting transistors, and even electrically pumped organic lasers. In this context, an overview of these fantastic advancements in terms of the fundamental insights into developing high performance organic semiconductors, efficient strategies for yielding desirable high quality OSSCs, and their applications in optoelectronic devices and circuits is presented. Finally, an overview of the development of OSSCs along with current challenges and future research directions is provided.
author_names: Xiaotao Zhang

Huanli Dong

Wenping Hu
title: Organic Semiconductor Single Crystals for Electronics and Photonics.
venue: Advanced materials
year: 2018

abstract: The large scale growth of semiconducting thin films forms the basis of modern electronics and optoelectronics. A decrease in film thickness to the ultimate limit of the atomic, sub nanometre length scale, a difficult limit for traditional semiconductors (such as Si and GaAs) would bring wide benefits for applications in ultrathin and flexible electronics, photovoltaics and display technology. For this, transition metal dichalcogenides (TMDs) which can form stable three atom thick monolayers, provide ideal semiconducting materials with high electrical carrier mobility, and their large scale growth on insulating substrates would enable the batch fabrication of atomically thin high performance transistors and photodetectors on a technologically relevant scale without film transfer. In addition, their unique electronic band structures provide novel ways of enhancing the functionalities of such devices, including the large excitonic effect, bandgap modulation, indirect to direct bandgap transition, piezoelectricity and valleytronics. However, the large scale growth of monolayer TMD films with spatial homogeneity and high electrical performance remains an unsolved challenge. Here we report the preparation of high mobility 4 inch wafer scale films of monolayer molybdenum disulphide (MoS2) and tungsten disulphide, grown directly on insulating SiO2 substrates, with excellent spatial homogeneity over the entire films. They are grown with a newly developed, metal organic chemical vapour deposition technique, and show high electrical performance, including an electron mobility of 30 cm2 V 1 s 1 at room temperature and 114 cm2 V 1 s 1 at 90 K for MoS2, with little dependence on position or channel length. With the use of these films we successfully demonstrate the wafer scale batch fabrication of high performance monolayer MoS2 field effect transistors with a 99% device yield and the multi level fabrication of vertically stacked transistor devices for three dimensional circuitry. Our work is a step towards the realization of atomically thin integrated circuitry.
author_names: Kibum Kang

Saien Xie

Lujie Huang

Yimo Han

Pinshane Y Huang

Kin Fai Mak

Cheol-Joo Kim

David A Muller

Jiwoong Park
title: High mobility three atom thick semiconducting films with wafer scale homogeneity
venue: Nature
year: 2015

abstract: With the rapid growth in the requirement for emerging photovoltaic technology like semitransparent solar cells applied for integrated smart windows, there is an urgent need to develop near infrared (NIR) non fullerene acceptors (NFAs) To address this issue, thieno[3,4 b]thiophene (TT) which has a stable quinoid structure to minimize the energy difference between two resonance structures corresponding to the band gap, is introduced into the push pull molecular architecture as a bridge unit to narrow the band gap of the derived acceptors. Due to the different linkage positions (4 or 6 position) of asymmetric TT, these acceptors are classified into two types of isomers, namely 4TIC, 4T4F, 6TIC and 6T4F, of which all have strong absorption in the NIR range. By incorporation with polymer donor PTB7 Th, the devices based on 6 position isomers exhibit superior photovoltaic performance, wherein a champion device based on 6T4F is obtained with a power conversion efficiency of 10.74% With detailed investigations on inherent optoelectronic properties as well as structural and morphological variation, this performance diversity induced by isomerism is determined by the evident difference in the packing order, which will impact the charge mobility and fill factor. This work presents a class of high performance NIR acceptors in which the regioisomeric backbone will significantly impact the optoelectronic properties.
author_names: Zeqi Zhang

Tong Shan

Yinan Zhang

Lei Zhu

Ling-wei Kong

Feng Liu

Hongliang Zhong
title: Isomerizing thieno[3,4 b]thiophene based near infrared non fullerene acceptors towards efficient organic solar cells
year: 2020