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To achieve green solution-processed thermally activated delayed fluorescence (TADF) organic light emitting diodes (OLEDs) with low turn-on voltages and high power efficiencies (PEs), an interfacial exciplex system 4,4′-N,N′-dicarbazolylbiphenyl (CBP)/(1,3,5-triazine-2,4,6-triyl)tris(benzene-3,1-diyl)tris(diphenylphosphineoxide) (PO-T2T) was used as the host to sensitize TADF emitters. Due to barrier-free hole-electron injection and effectively energy transfer, green solution-processed OLED with interfacial CBP:PO-T2T host exhibits a low turn-on voltage of 3.0 V and maximum current efficiency (CE), PE and external quantum efficiency (EQE) of 53.4 cd/A, 41.9 lm/W and 16.2% by using our previous reported TADF molecule 2’-(10H-phenoxazin-10-yl)-[1,1’:3′,1″-terphenyl]-4,4″,5′-tricarbonitrile (oPTBC) as the emitter. And the compared OLEDs based on the bulk CBP:PO-T2T host and single CBP host exhibit relatively high turn-on voltages of 4.3 and 3.7 V and low maximum PEs of 20.8 and 33.0 lm/W. Moreover, the OLED based on classic green TADF emitter 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) achieves high performance with an ultralow turn-on voltage of 2.9 V and high maximum CE, PE and EQE of 67.2 cd/A, 62.1 lm/W and 20.0%, respectively. These results are remarkable among the reported green solution-processed TADF-OLEDs and demonstrate the superiority of interfacial exciplex host in solution-processed OLEDs.

High triplet energy of exciplex was achieved successfully by modifying conventional electron-donating (D) molecule TCTA. So, in this work, Ph-O-TCTA was designed and synthesized. Ph-O-TCTA: PhPO could efficiently form an exciplex. The solution-processed blue phosphorescent and thermally activated delayed fluorescent (TADF) OLEDs have been realized with the maximum current efficiencies above 30 cd A−1 by employing exciplex Ph-O-TCTA: PhPO as a host.

An alcohol additive 1, 8-Octanediol (ODO) with a simple carbon chain structure was first introduced into the light-emitting layer (LEL) of solution-processed small molecule organic light-emitting diodes (OLEDs) in this work. We found a typical host material of CBP presented a micro-aggregation film state with low percent of ODO adding in the LEL. The corresponded solution-processed devices with the LEL of CBP and 4CzIPN were investigated. The reduced device turn-on voltage and improved efficiency was achieved with low percent addition of 2 wt% ODO in LEL. Moreover, in the atmosphere, the device with ODO additive showed alleviated device degradation compared to no additive device. These results demonstrate the micro-aggregated state of the host is helpful, which can be attributed to the better charge transfer ability. Significantly, this additive process was also applied to other devices with reduced device turn-on voltage and improved efficiency.

In this study, solution-processed blue organic light-emitting diodes (OLEDs) were constructed by employing POBPCz as a bipolar host material with a high triplet of 3.01 eV and 2CzPN as the blue TADF emitter. A maximum EQE of 12.9% was realized in the blue TADF OLEDs, along with a satisfactory CIE coordinate of (0.19, 0.37). These results were among the best ones for the 2CzPN-based solution processed blue OLEDs. Moreover, solution-processed white OLEDs (WOLEDs) with a single-emitting layer were fabricated by Ir(MDQ)2 (acac) as the orange-red iridium complex. The optimized WOLEDs could achieve a maximum EQE of 12.4%, as well as the stable electroluminescence spectra. Notably, the white-light emission was achieved by the incomplete energy transfer from the blue TADF emitter of 2CzPN to the orange-red emitter of Ir (MDQ)2 (acac) via Forster energy transfer (FRET) process.

Organic electronics is one of the most promising technologies for creating flexible electronic devices using low temperature plastic compatible processes. However, contact resistances of organic transistors remain one of the most significant hurdles to achieving high performance circuits in this technology. Short channel devices (

Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) hole contact is widely used in organic solar cells (OSCs). In this work, we report the effort to develop a versatile solution-processed molybdenum trioxide (s-MoO3)/Au nanoparticles (NPs)/s-MoO3 (MAM) hole contact for application in PEDOT:PSS-free OSCs. The use of Au NPs is to improve the adhesion between the two s-MoO3 layers in the MAM hole contact. It shows that MAM hole contact enables to enhance the charge extraction through suppression of bimolecular recombination, and reduce the leakage current by improvement of contact property. Power conversion efficiency of 7.68% was obtained for MAM-based OSCs, with a blend system of poly[[4,8-bis[(2-ethylhexyl) oxy]benzo[1,2-b: 4,5-b’] dithiophene-2,6-diyl] [3-fluoro-2-[(2-ethylhexyl) carbonyl] thieno[3,4-b]-thiophenediyl]]: [6,6]- phenyl-C70-butyric-acid-methyl-ester, which is comparable to that of the PEDOT:PSS-based cells (7.48%). It demonstrates clearly that solution-processed MAM hole contact can be readily adopted to replace the widely used acidic PEDOT:PSS hole contact for application in PEDOT:PSS-free OSCs.

Flexible organic field-effect-transistor (OFET) memory is one of the promising candidates for next-generation wearable nonvolatile data storage due to its low price, solution-processability, light-weight, mechanically flexibility, and tunable energy level via molecular tailoring. In this paper, we report flexible nonvolatile OFET memory devices fabricated with solution-processed polystyrene-brush electret and organic semiconductor blends of p-channel 6, 13-bis-(triisopropylsilylethynyl)pentacene (TIPS-PEN) and n-channel poly-{[N,N′-bis(2- octyldodecyl)-naphthalene-1,4,5,8-bis-(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} (P-(NDI2OD-2T); N2200). Fabricated flexible OFET memory devices exhibited high memory window (30 V) and ON/OFF current ratio (memory ratio) over 103. Furthermore, we obtained reliable memory ratio (~103) over retention time of 108 s, 100 times of repeated programming/erasing cycles, and 1000 times of bending tests at a radius of 3 mm.

Organic light-emitting diodes (OLEDs) fabricated with thermally activated delayed fluorescence materials usually suffer from serious efficiency roll-offs at high voltages, which restrain their practical applications. To address this issue, in this work, we design and synthesize two luminogens composed of electron-withdrawing benzoyl, electron-donating phenoxazine and 9,9-dimethyl-9,10-dihydroacridine, and dendritic tris(4-(9H-carbazol-9-yl)phenyl)amine. The thermal stabilities, energy levels, electronic structures, photophysical properties and electroluminescent performance of both luminogens are investigated and discussed. They display enhanced fluorescence with greatly increased delayed component under aggregated states, demonstrating the aggregation-induced delayed fluorescence property. Vacuum-deposited and solution-processed OLEDs were fabricated by using both luminognes as emitters, which provided high external quantum efficiencies of 16.9% and 10.7%, respectively, with the negligible efficiency roll-offs.

We propose a flexible proximity sensor to detect sub-centimeter distance with an ultra-high displacement resolution. The proximity sensor is realized by integrating a semi-transparent organic photo detector with a transparent top electrode and a finger-type bottom electrode. By placing the semi-transparent finger-type photodetector on a light source, such as a light-emitting diode (LED), the photodetector can detect the light reflected from an object on top of the sensor. With the highly compact structure, the detecting range is from 1 mm to 30 mm. From 1 mm to 10 mm, the sensor is particularly sensitive and delivers a resolution of 1 mm. The air-stable photodetector can also be fabricated on a flexible substrate without encapsulation, enabling the integration with arbitrary light sources. After 1000 times bending, the flexible photodetector shows no obvious degradation.

Solution-processed organic light-emitting devices (OLEDs) still require improvements in their operational lifetime in order for them to become commercially viable. One factor that limits the lifetime of these devices is the instability of the hole injection layer (HIL). Therefore, understanding its degradation mechanism is crucial for the development of more stable solution-processed OLEDs. In this work, we use an archetypal fluorescent OLED in conjunction with an experimental solution-processed HIL in order to elucidate the degradation mechanism in these HILs. Our studies show that degradation is caused by triplet excitons. This new triplet-induced hole injection degradation is expected to be a common phenomenon in OLEDs, and therefore should have important implications for the design of stable HILs.

Two new oligothiophene-based small molecules, namely DRCN6T-F and DRCN8T-F , with 3,3′-difluoro-2,2′-bithiophene as the central building block and 2-(1,1-dicyanomethylene)-rhodanine as end groups, were designed and synthesized. Compared to their non-fluorinated counterparts DRCN6T and DRCN8T , DRCN6T-F and DRCN8T-F exhibit enhanced intermolecular interactions and lower HOMO energy levels. However, PCEs of 2.26% and 5.07% were obtained for DRCN6T-F and DRCN8T-F based optimized devices, respectively, lower than those of non-fluorinated molecules DRCN6T and DRCN8T . The relatively poor performance for the DRCN6T-F and DRCN8T-F were mainly caused by their low short-circuit current densities, due to their unfavorable morphologies and low charge carrier mobilities.

Two oligothiophene based small molecules (DINER5T and DINER7T) with a new end group INER were synthesized as the donors for organic solar cells, and their photovoltaic performance was studied and compared with the corresponding compounds (DRHD7T and DIN7T) with the same backbone structure but different end groups. Both of the new molecules exhibit broad and red shift absorption compared with DRHD7T and DIN7T, with very low band gaps of 1.47 eV and 1.34 eV, respectively. The devices based on DINER5T:PC71BM and DINER7T:PC71BM blend films gave PCEs of 4.22% and 4.02%, respectively, through a solvent vapor annealing (SVA) process with CH2Cl2.

Two new small molecules, namely DRSBDTT-EH and DRSBDTT-BO, with alkylthio thienyl substituted benzodithiophene as the central unit and 3-ethylrhodanine as end groups, were designed and studied as the donors for solution processed organic solar cells. The optimized device based on DRSBDTT-EH bearing shorter alkylthio chain gave a power conversion efficiency (PCE) of 8.78%, which is slightly higher than that of device (8.53%) based on DRSBDTT-BO with longer alkylthio chain.

International audience; Polymer light emitting diodes (PLEDs) have attracted a great deal of interest within academia and industry because of their potential applications in flat panel displays and solid-state lighting technologies. The solution processability of polymers offers the advantages of simple and mild fabrication conditions enabling to cut cost and produce large area displays. Among all polymeric hosts under investigation, carbazole-based materials benefit from the wide bandgap of carbazole as well as its remarkable thermal, photochemical and chemical stability. Especially, the relatively high triplet energy level of carbazole makes it an appealing candidate to design hosts for wide bandgap triplet emitters such as blue dopants. In this review, an overview of all carbazole-based polymeric hosts reported to date is presented. Noticeably, easiness of synthesis has been an aspect largely developed to access to these polymeric structures

To achieve high efficiency solution processed red OLED, a series of new triphenylamine–functionalized dithienylbenzothiadiazoles, namely TB , T3TB and T4TB , as non-doped solution-processed hole-transporting red emitters were synthesized and characterized. Particularly, T3TB having five triphenylamine units substituted on the dithienylbenzothiadiazole core exhibited a good red emission with high T g amorphous and good film-forming properties. A simple structured non-doped red OLED (ITO/PEDOT:PSS/ T3TB (spin coating)/BCP/LiF–Al) with an efficiency ( η ) of 6.25 cd A −1 at 4.1 mA cm −2 (PE = 5.17 lm W −1 ), a low turn-on voltage (3.0 V) and a pure red emission ( λ EL = 656 nm, CIE ( x , y ) = 0.67, 0.33) was attained.

A solution-processable A–D–A structure small molecule donor material called DRCN7T-Se with selenophene as the central block was synthesized. Conventional bulk-heterojunction solar cell devices based on DRCN7T-Se and PC71BM were optimized by thermal annealing and an excellent power conversion efficiency of 8.30% was achieved under AM 1.5G irradiation (100 mW cm−2).

A new linear dithienosilole-based oligothiophene end-capped with methyl and electron-withdrawing dicyanovinyl groups, DTS(Oct) 2 -(2T-DCV-Me) 2 , was prepared in good yield. This oligomer exhibited broad absorption spectra in bulk down to the near-IR region with the optical edge at 900 nm, resulting in an initially high power conversion efficiency of 5.44% in solution-processed organic solar cells using PC 71 BM as an acceptor.

Low-voltage organic phototransistors (OPTs) are attractive candidates for optoelectronic applications such as photodetectors and memory devices. Here we describe a solution-processed low-voltage organic phototransistor based on a triethylgermylethynyl-substituted anthradithiophene (diF-TEG ADT). Two kinds of dielectric materials were used: 80-nm-thick potassium alumina (PA) and 300-nm-thick thermally grown SiO2. To investigate its application in a moist environment, the performance at different humidities was characterized. Results showed that the device was very stable in high humidity. A major change in drain current (IDS) was observed when connecting or disconnecting the gate electrode to the device. This feature may motivate the application of diF-TEG ADT-based phototransistors as multistage photo-controlled memory devices.

To deposit organic semiconducting crystals from solution, we propose the use of a rollerball pen as a simple and promising tool. These organic crystal grains of dioctylbenzothienobenzothiophene measured several hundred micrometers. The fabricated OFETs exhibited good device performance with a field-effect mobility (μFET) of 0.7 cm2/Vs and an on-off ratio of more than 107. Simulation results reveal that the flow behavior of solution from the pen refill tube to the substrate intrinsically enhances the formation of large organic crystals.

A new aqueous based polymer, Plexcore® OC AQ1200 (AQ1200) was used as a hole injection layer (HIL) in organic light emitting diodes (OLEDs) and the device results are compared with polyethylene dioxythiophene:polystyrene sulfonate (PEDOT:PSS) in terms of injection efficiency and stability. Dark injection transient measurements show a higher injection efficiency in hole-only devices using AQ1200 HIL compared with PEDOT:PSS. Using AQ1200 as an HIL, high efficiency phosphorescent OLEDs are demonstrated to have a long lifetime, with an estimated operational half lifetime (LT 50) of more than 8000 h from an initial luminance of 1000 cd/m 2 .

A highly-sensitive organic phototransistor, based on solution-processed 2,8-difluoro-5,11-bis(triethylsilylethynyl) anthradithiophene (diF-TESADT) was fabricated and investigated for an optical sensing element. The phototransistor based on thin crystalline grains of diF-TESADT exhibited a significant threshold voltage ( V TH ) shift under a white light illumination in which the response time was estimated to be 6 . It was found that the V TH shift can be further enlarged by an additional gate bias, achieving very high light responsivity >10 3 A/W at 0.17 mW/cm 2 and I PH / I DARK ratio higher than 10 6 . Also, by applying an erase gate bias, fast recovering of V TH to the initial position was possible. This phenomenon can be ascribed to the trapping and de-trapping of photo-generated carriers at the organic channel/dielectric interface, while the amount of trapped carriers can be also modulated simultaneously by the gate bias. This investigation identifies that the solution-processed diF-TESADT phototransistors can be used for large-area and low-cost optical sensors and memory applications. In particular, it can be claimed that performance improvement by a gate bias represents a universal method applicable to the organic phototransistors.

A cross-linkable hole transporting material PLEXCORE® HTL was incorporated in phosphorescent organic light emitting diodes. This hole transporting material is based on an arylamine derivate. The device performance in terms of efficiency and lifetime was compared to the same devices with a thermally evaporated 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB)-based hole transporting layer. The resulting devices with the cross-linkable HTL gave higher efficiency, smaller roll-off and longer lifetime compared with devices with the NPB-based devices. This new hole transporting material paves the road toward solution processed multilayer light emitting devices.

This study demonstrates the incorporation of a Cs 2 CO 3 :conjugated polyelectrolyte blended interfacial layer between the emissive layer and a silver (Ag) cathode, for realizing all-solution processed polymer light-emitting diodes. For a device with poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) as the emissive layer, this approach improves the maximum luminance of approximately 80,000 cd/m 2 and maximum current efficiency of 10.6 cd/A. It is clarified that the interfacial layer prevents Ag nanoparticles from penetrating into the emissive layer, resulting in yellow–green emission from F8BT. We also demonstrate the possibility of all-solution processed polymer light-emitting diodes utilizing solution-processed Cs 2 CO 3 :conjugated polyelectrolyte interfacial layer and Ag nano-ink.

Single-crystalline organic transistors of 3,11-didecyl-dinaphtho[2,3- d :2′,3′- d ′]benzo[1,2- b :4,5- b ′]dithiophene (C 10 -DNBDT-NW) and 2,9-didecyl-dinaphtho[2,3- b :2′,3′- f ]thieno[3,2- b ]thiophene (C 10 -DNTT) were fabricated by solution processes on top of the patterned hybrid ultrathin gate dielectrics consisting of 3.6 nm-thick aluminum oxide and self-assembled monolayers (SAMs). Due to the excellent crystallinity of the channel films, bottom-gate and top-contact field-effect transistors exhibited the average field-effect mobility of 3.7 cm 2 /V s and 4.3 cm 2 /V s for C 10 -DNBDT-NW and C 10 -DNTT, respectively. These are the first successful devices of solution-processed single-crystalline transistors on ultrathin gate dielectrics with the mobility above 1 cm 2 /V s, opening the way to develop low-power-consumption and high-performance printed circuits.

This paper presents a model for the simulation of gate leakage currents within organic thin film transistors. These unintended currents act as loads within integrated electronic circuits and thereby can have a huge impact on its functionality. Simulation of these currents is important in order to design and manufacture high performance organic electronics circuits of high complexity. We show the influence of gate leakage currents on signals within a circuit. A model for electrical simulations is developed, which is based on defects within the dielectric layer. Only two new parameters need to be determined, they describe the size and amount of defects. The improvement of simulation by this model is verified by comparison of measurements and simulations.

A novel deep HOMO A(1)-pi-A(2)-D-A(2)-pi-A(1) type molecule (D(CATBTzT)BDT), which terminal electron-withdrawing octyl cyanoacetate group is connected to a benzo[1,2-b:4,5-b'] dithiophene (BDT) core through another electron-accepting benzotriazole block, has been synthesized, characterized, and employed as electron donor material for small molecule organic solar cells (SM-OSCs). By simple solution spin-coating fabrication process, D(CATBTzT) BDT/PC61BM based OSCs exhibit a power conversion efficiency (PCE) of 3.61% with a high open-circuit voltage of 0.93 V. The D(CATBTzT) BDT based solar cells device also can show high FF of 72% with PCEs of 2.31% which is one of the best FF results for solution-processed SM-OSCs. (C) 2013 Elsevier B.V. All rights reserved.

Solution processing of low-molecular weight organic materials for optoelectronic devices is a challenging task due to often strong molecular aggregation. We present a facile and universal route for suppressing the aggregation of molecules during wet-deposition of emission layers for organic light emitting diodes by incorporating electronically inactive polymers. Moderate polymer concentrations of about 10 wt.% lead to only minor changes of the electrical performance while at the same time improving the film formation and consequently the device luminance significantly. The device performance matches the performance of vacuum processed devices with the same device architecture.

A solution processable A-D-A-D-A structure small molecule DCAEH5TBT using a BT unit as the core has been designed and synthesized for application in BHJ solar cells. The device employing DCAEH5TBT/PC 61BM as active layer shows PCE of 2.43% without any post treatment. After thermal annealing (150 C, 10 min), the PCE of this molecule based device increased to 3.07%, with Jsc of 7.10 mA/cm 2 , Voc of 0.78 V and FF of 55.4%, which indicates

Solution processed silver nanowire meshes (Ag NWs) were laminated on top of solid-state dye-sensitized solar cells (ss-DSCs) as a reflective counter electrode. Ag NWs were deposited in

We report operational and environmental stability of solution-processed organic thin film transistors (OTFTs) using the small molecule organic semiconductor 6,13-bis(triisopropyl-silylethynyl) pentacene (TIPS-pentacene). Typical drop-cast TIPS-pentacene OTFTs show strong molecular ordering and relatively stable characteristics with air and illumination compared to vapor-deposited pentacene OTFTs. For short channel length devices, TIPS-pentacene OTFTs undergo significant degradation with bias-stress, possibly due to operation at large drive currents and large local power dissipation as well as built-in charges in the channel area.

Interfacial layers are commonly employed in organic photovoltaic (OPV) cells in order to improve device performance. These layers must be transparent, stable, be compatible with the photo-active materials and provide efficient charge extraction with a good energetic match to the relevant organic material. In this report we demonstrate the compatibility of zirconium acetylacetonate (ZrAcac) electron extracting layers in both regular and inverted small molecule OPV cells. When the ZrAcac was processed in both air and under N2, low work function (3.9 and 3.7 eV respectively), highly transparent layers were formed, with good energetic alignment to both C60 and hexachlorinated boron subphthalocyanine chloride (Cl6-SubPc) acceptors. Initial measurements indicate similar stabilities when using the ZrAcac in either device architecture. These results indicate that the ZrAcac layer can be used as a direct replacement for the commonly used bathocuproine (BCP) in small molecule OPV cells.