Multifunctional 4,5-Diphenyl-1H-imidazole-Based Luminogens as Near UV/Deep Blue Emitters/Hosts for Organic Light-Emitting Diodes and Selective Picric Acid Detection

A series of luminophores (construction of diphenylimidazole (m-CF3PTPI) groups functionalized at the N1-positions of imidazole groups) were purposefully designed and synthesized for optoelectronics and for selective detection of nitroaromatic compounds. The luminophores showed deep blue emission in solution, solid, and thin-film matrix with acceptable quantum yield and good thermal stability (5% weight loss at 258–296 °C). From electrochemical analysis as well as theoretical calculations, the energy gaps of HOMO–LUMO are found to be in good agreement and all of them showed good triplet energy. The luminophores can be explored as hosts for phosphorescent organic light-emitting diodes (PhOLEDs). Furthermore, the m-CF3PTPI derivatives were used as emitters for fluorescent OLEDs and hosts (m-CF3PTPI-1 and m-CF3PTPI-2) for triplet dopants in PhOLEDs. Near-UV emissions were observed for all the doped devices that exhibited electroluminescence (EL) peaks at ∼380–395 nm with a Commission International deL’Eclairage (CIEy) coordinate of ∼0.09. Of all the devices, the m-CF3PTPI-5 (3 wt %)-based device demonstrated a maximum external quantum efficiency (EQEmax) of 2.8%, power efficiency (PEmax) of 0.9 lm/W, current efficiency (CEmax) of 1.3 cd/A, and brightness of 953 cd/m2. Moreover, the device was further optimized using a different host approach. SimCP2 displayed the best performance by achieving a high EQEmax of 4.0% that is near the theoretical limit of fluorescent materials

Enabling Lambertian-Like Warm White Organic Light-Emitting Diodes with a Yellow Phosphor Embedded Flexible Film

We demonstrate in this report a new constructive method of fabricating white organic light-emitting devices (OLEDs) with a flexible plastic film embedded with yellow phosphor. The flexible film is composed of polydimethylsiloxane (PDMS) and fabricated by using spin coating followed by peeling technology. From the results, the resultant electroluminescent spectrum shows the white OLED to have chromatic coordinates of 0.38 and 0.54 and correlated color temperature of 4200 K. The warm white OLED exhibits the yield of 10.3 cd/A and the luminous power efficiency of 5.4 lm/W at a luminance of 1000 cd/m2. A desirable Lambertian-like far-field pattern is detected from the white OLEDs with the yellow phosphor containing PDMS film. This method is simple, reproducible, and cost-effective, proving to be a highly feasible approach to realize white OLED

High-efficiency flexible white organic light-emitting diodes

[[abstract]]A high-efficiency flexible white organic light-emitting diode (OLED) was fabricated using effective device structure on high glass-transition plastic substrate with a thin silicon dioxide pre-coat and highly conductive indium tin oxide (ITO) deposited by radio frequency magnetron sputtering at elevated temperature. Sputtering ITO at 200 degrees C on a 150 angstrom SiO2-modified polyethersulfone yielded a high power efficiency of 6.51m/W at 800 cd m(-2) and a maximum external quantum efficiency of 3.2% with a pure-white emission of (0.321, 0.339). Besides device structure, the power efficiency of the flexible OLEDs depends strongly on the conductivity of ITO, which in turn depends on its surface topology, which can be most effectively improved by adding a SiO2 pre-coat of optimal thickness.[[fileno]]2020306010050[[department]]材料

Bending beam measurement of moisture diffusion in polyimide films on silicon substrate

[[abstract]]A theoretical model, correlating the bending curvature variation ratio of a layered structure caused by moisture-induced-swelling in its polymer overcoat with time under Case I diffusion, has been developed. This model has considered the pre-existing intrinsic strain in the polymer film upon deposition. According to this model, any specimen to be studied does not need to be bending or strain free. Furthermore, an useful and relatively simplified formula has been derived therefrom and used in identifying the diffusions of moisture in the films of two rod-like and one semi-flexible polyimides, their blends, and a random copolyimide. In PMDA-ODA (pyromellitic dianhydride-4,4 prime -oxydianiline), the diffusion constant, D, is 4.64 × 10-9 cm2 s-1. In PMDA-PDA (p-phenylenediamine), D = 1.25 × 10-9, and in PMDA-B (-benzidine) 0.10 × 10-9 cm2 s-1. The diffusion fastest in PMDA-ODA can be attributed to its amorphous structure, and slowest in PMDA-B to its small interchain spacing. The diffusion in a random copolymer with 50 wt% PMDA-PDA and 50 wt% PMDA-B is faster than in the blend with 60 wt% PMDA-PDA and 40 wt% PMDA-B. This can be attributed that the random copolyimide film is more amorphous according to an X-ray diffractometry study.[[fileno]]2020306010018[[department]]材料科學工程學

High-Efficiency Phosphorescent and Fluorescent Pure-White Organic Light-Emitting Diodes by Incorporating Small Nano-Dot in Non-emissive Layer

[[sponsorship]]應用科學研究中心[[note]]已出版;[SCI];有審查制度;不具代表性[[note]]http://gateway.isiknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Drexel&SrcApp=hagerty_opac&KeyRecord=0916-8524&DestApp=JCR&RQ=IF_CAT_BOXPLO

Sunlight-style color-temperature tunable organic light-emitting diode

[[abstract]]We demonstrate a man-made lighting device of organic light-emitting diode (OLED) capable of yielding a sunlight-style illumination with various daylight chromaticities, whose color temperature ranges between 2300 and 8200 K, fully covering those of the entire daylight at different times and regions. The OLED employs a device architecture capable of simultaneously generating all the emissions required to form a series of daylight chromaticities. The wide color-temperature span may be attributed to that the recombination core therein can easily be shifted along the different emissive zones simply by varying the applied voltage via the use of a thin carrier-modulating layer. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3176217][[fileno]]2020306010052[[department]]材料