361wileyonlinelibrary.com phosphorescent OLEDs (PhOLEDs) with both high external quantum effi ciency (EQE) and power effi ciency (PE) by tuning the electrical balance, confi ning the excitons in the emitting layer (EML), and reducing the operating voltage of the devices. For example, a large number of host materials with higher triplet (T 1 ) level than that of a blue emitter have been synthesized for a blue EML, and the mixed host systems or dual EMLs have been utilized to achieve good charge balance and exciton confi nement. [24][25][26][27][28][29] New electron or hole transporting materials with high T 1 level adjacent to an EML have also been introduced to confi ne excitons in the EML. [ 5,8,18,[30][31][32][33][34] Moreover, the electrical doping in the injection layers and synthesis of organic materials with high mobility and proper energy level were reported to reduce the operating voltage. [ 14,17,23,31,32,34 ] As a result, the highly effi cient blue PhOLED with a maximum EQE of 30% was reported, [ 22 ] but the device showed large effi ciency rolloff at high luminance and high driving voltage. There are still challenging issues to realize blue PhOLEDs with high EQE, PE, and low effi ciency roll-off at the same time.Use of an exciplex forming co-host is a promising approach to resolve the issues. The effi cient energy transfer from an exciplex forming co-host to phosphorescent dye resulted in high effi ciencies approaching the theoretical limits, low driving voltages, and low effi ciency roll-offs, simultaneously, with a simple structured device. [34][35][36][37][38][39][40] Green, orange and red PhOLEDs and a fl uorescent OLED with EQEs over 30% have been reported, [35][36][37][38][39][40][41][42] but these exciplex forming systems are not applicable to blue dopants because of the higher T 1 level of blue dopants than the T 1 level of exciplexes.The following is required for an exciplex forming co-host for effi cient phosphorescent OLEDs: 1) T 1 level of an exciplex has to be lower than those of the consisting molecules in order to confi ne the excitation energy in the exciplex state, not to be transferred to the consisting molecules, and 2) T 1 level of an exciplex has to be higher than that of a phosphorescent dopant to utilize the energy transfer from the exciplex to a blue dopant. However, seeking for an ideal exciplex system meeting the requirements for a blue dopant seemed to be a challenging issue. [43][44][45] The exciplex forming co-host with phosphorescent dopant system has potential to realize highly effi cient phosphorescent organic light emitting didoes (PhOLEDs). However, the exciplex forming co-host for blue phosphorescent OLEDs has been rarely introduced because of higher triplet level of the blue dopant than green and red dopants. In this work, a novel exciplex forming co-host with high triplet energy level is developed by mixing a phosphine oxide based electron transporting material, PO-T2T, and a hole transporting material, N , N ′-dicarbazolyl-3,5-benzene (mCP). Photo-physical analysi...

In this letter, we investigate the impact of the light illumination on the stability of indium–gallium–zinc oxide thin film transistors under positive gate-bias stress. The noticeable decrease in threshold voltage (Vt) shift more than 5.5 V under illuminated positive gate-bias stress indicates a superior reliability in contrast with the dark stress. The accelerated Vt recovery characteristic compared with dark recovery demonstrates that the charge detrapping effect was enhanced under illumination. Furthermore, the average effective energy barrier of charge trapping and detrapping was derived to verify that illumination can excite the trapped charges and accelerate the charge detrapping process.

A post-treatment using N2O-plasma is applied to enhance the electrical characteristics of amorphous indium gallium zinc oxide thin film transistors. Improvements in the field-effect mobility and the subthreshold swing demonstrate that interface states were passivated after N2O-plasma treatment, and a better stability under positive gate-bias stress was obtained in addition. The degradation of mobility, resulted from bias stress, reduces from 6.1% (untreated devices) to 2.6% (N2O-plasma treated devices). Nevertheless, a strange hump characteristic occurs in transfer curve during bias stress, inferring that a parasitic transistor had been caused by the gate-induced electrical field.

A study on a two-bed six-step pressure swing adsorption (PSA) process using zeolite 5A was performed experimentally and theoretically for bulk separation of H2/CO and H2/CH4 systems (70/30 vol %) as major components in coke oven gas. When the pressure is cycled between 1 and 11 atm at ambient temperatures, 70% H2 in the feed could be concentrated to 99.99% in the product with a recovery of 75.87% in the H2/CO mixture and 80.38% in the H2/CH4 mixture. The effects of adsorption pressure, P/F ratio, adsorption/purge step time, and pressure equalization step time were investigated experimentally. If the product end of an adsorption bed was not contaminated during the adsorption and depressurizing pressure equalization steps, elongation of both the adsorption and purge steps gave good adsorbent productivity and recovery without any decrease in purity. Certain elongations of step time in the pressure equalization step resulted in a better performance of a PSA process. When the H2 mole fraction of effluent stream during the pressure equalization step was not high, the initial H2 purity of the adsorption step was not good because of the contamination of the product end section. These results were analyzed by a mathematical model incorporating heat and momentum balances.

We demonstrate the fabrication of solution-processed MoOx-treated (s-MoOx) silver nanowire (AgNW) transparent conductive electrodes (TCEs) utilizing low-temperature (sub-100 °C) processes. The s-MoOx aggregates around the AgNW and forms gauze-like MoOx thin films between the mesh, which can effectively lower the sheet resistance by more than two orders of magnitude. Notably, these s-MoOx-treated AgNW TCEs exhibit a combination of several promising characteristics, such as a high and broad transmittance across a wavelength range of 400 to 1000 nm, transmission of up to 96.8%, a low sheet resistance of 29.8 ohm sq(-1), a low haze value of 0.90%, better mechanical properties against bending and adhesion tests, and preferable gap states for efficient hole injection in optoelectronic applications. By utilizing these s-MoOx-treated AgNW TCEs as the anode in ITO-free organic light emitting diodes, promising performance of 29.2 lm W(-1) and 10.3% external quantum efficiency are demonstrated. The versatile, multi-functional s-MoOx treatment presented here paves the way for the use of low-temperature, solution-processed MoOx as both a nanowire linker and a hole injection interfacial layer for future flexible optoelectronic devices.