In this work, the multilayer organic light emitting transistors (OLETs) based on high‐k polymer crosslinked poly(vinyl alcohol) (C‐PVA) as the dielectric layer are studied. The devices show an excellent brightness of 14 500 cd m−2 and a record breaking external quantum efficiency (EQE) of about 9.0% in inert atmosphere. The use of perfluoro(1‐butenyl vinyl ether) polymer (CYTOP) modified C‐PVA as a hydrophobic dielectric affords OLETs with good stability, displaying a maximum brightness of 13 400 cd m−2 and EQE of 7.31% in ambient conditions with high humidity (relative humidity RH = 70%). Furthermore, the flexible OLETs based on CYTOP/C‐PVA dielectric layer show a brightness of 8300 cd m−2 and a peak EQE at 9.01%, which is the first reported flexible OLET with >500 cd m−2 brightness. The excellent OLET device performance is ascribed to the excellent hole transport structure, high efficiency of guest–host system, and the better carrier balance in the emitting layer, which could be a practical strategy to develop high‐performance flexible OLETs. It is proven for the first time that OLETs could achieve such high EQE and brightness, even for flexible OLETs, paving the way for their future application in industry.
Light‐emitting transistors (LETs) have attracted tremendous academic and industrial interest due to their dual functions of electrical switching and light emission in a single device, which can considerably reduce system complexity and manufacturing costs, especially in the area of flat panel and flexible displays as well as lighting and lasers. In recent years, enhanced LET performance has been achieved by introducing multiple‐layer heterostructures in the charge‐carrying/light‐emitting LET channel versus the best‐reported performance in single active layer LETs, rendering multi‐layer LETs promising candidates for next‐generation display technologies. In this review, the fundamental structures and working principles of multi‐layer heterostructure LETs are introduced. Next, developments in multi‐layer LETs are discussed based on co‐planar LETs, non‐planar LETs, and vertical LETs including organic, quantum dot, and perovskite light emitters. Finally, this review concludes with a summary and a perspective on the future of this research field.
Organic field-effect transistors (OFETs) have acquired increasing attention because of their wide range of potential applications in electronics; nevertheless, high operating voltage and low carrier mobility are considered as major bottlenecks in their commercialization. In this work, we demonstrate low-voltage, flexible OFETs based on ultrathin single-crystal microribbons. Flexible OFETs fabricated with 2,7-dioctylbenzothieno[3,2-b]benzothiophene (C8-BTBT) based solution-processed ultrathin single-crystal microribbon as the semiconductor layer and high-k polymer, polysiloxane–poly(vinyl alcohol) composite as an insulator layer manifest a significantly low operating voltage of −4 V, and several devices showed a high mobility of >30 cm2 V–1 s–1. Besides, the carrier mobility of the fabricated devices exhibits a slight degradation in static bending condition, which can be retained by 83.3% compared with its original value under a bending radius of 9 mm. As compared to the bulk C8-BTBT single-crystal-based OFET, which showed a large crack only after 50 dynamic bending cycles, our ultrathin single-crystal-based counterpart demonstrates a much better dynamic force stability. Moreover, under a 20 mm bending radius, the mobility of the device decreased by only 11.7% even after 500 bending cycles and no further decrease was observed until 1000 bending cycles. Our findings reveal that ultrathin C8-BTBT single-crystal-based flexible OFETs are promising candidates for various high-performance flexible electronic devices.
in several fields, such as computed tomography, security identification, and radiation detection. [1][2][3] Among them, inorganic scintillators (such as CaF 2 :Eu, CsI:Tl, Bi 4 Ge 3 O 12 , etc.) have been broadly utilized in industrial and medical applications due to the advantages of high radioluminescence (RL) intensity and excellent absorption coefficient. [4,5] However, the disadvantages of high processing temperature (>1700 °C), difficulty in large-area solution processing and poor biocompatibility, hinder their applications in novel flexible X-ray imaging and in vivo bioimaging. [4,6,7] Compared with inorganic scintillators, organic fluorescence counterparts showed abundant resource supplies, low-temperature large area solution processing, fast response time, intrinsic mechanical flexibility as well as low cost. [8][9][10][11][12][13] In 2011, Loef et al. reported a 9,10-diphenylanthracene (DPA) single crystal with light yields up to 20 000 ph MeV −1 (125% higher than anthracene) and fast decay time of 12 ns, which growth by solution method under a low temperature of 35 °C. [14] Recently, Chen et al. [4] further optimized the growth method of DPA single crystal and they found that DPA single crystal exhibited fast response time, high sensitivity, and fast photon-conversion efficiency. The fabricated devices showed high spatial resolution up to 20.00 lp mm −1 , which exhibited the potential application in X-ray detection and medical imaging. However, apart from the work mentioned above, most of the reported organic fluorescent scintillators exhibited quite low radioluminescence (RL) intensity and low sensitivity, which hindered their practical applications.For organic scintillators, X-ray-excited luminescence mainly goes through three processes (Scheme 1b): [12,15] (1) conversion stage, in which the electron-hole pairs are generated by exciting the inner electrons in molecular after absorbing X-rays; (2) transport stage, where the carriers are thermally transported to the luminogens; and (3) luminescence stage, in which carriers recombine to produce singlet (25%) and triplet excitons (75%), then produce light emission. For organic fluorescence materials, 75% of the triplet excitons cannot be utilized due to the spin prohibition of the phosphorescent emission process, which results in low light yield for the reported organic fluorescent scintillators. [16][17][18] Recently, Dong et al. studied the influence factors of the radioluminescence properties for three Organic fluorescence scintillators, owing to the ultrafast response time, versatile chemical structures, low processing temperature, and low cost, are considered as one of the promising materials for medical diagnostics, radiation detection, and X-ray astronomy. However, the low radioluminescence (RL) intensity and low sensitivity hinder their practical applications. In this work, a highly efficient organic fluorescent scintillator, 4,4′-bis(9-carbazolyl) biphenyl (CBP), is presented, exhibiting a high X-ray RL intensity, narrow full width at half-maxim...
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