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It is widely recognized that hybrid (organic/inorganic) light emitting diodes (LEDs) are of concern because they use an organic material instead of rare earth phosphors, but extending their lifetime remains challenging. To construct organic luminescent material with high photoluminescence quantum yield (PLQY), a compound named 1-(4-(tert-butyl)phenyl)-2-(4′-(1-phenyl-1H-benzo[d]imidazol-2-yl)-[1,1′-biphenyl]-4-yl)-1H-phenanthro[9,10-d]imidazole (TPBI-BPI) was synthesized by connect two imidazoles units. The PLQY of TPBI-BPI is 0.97 in acetonitrile. The white light emission (WLE) of TPBI-BPI in ethyl acetate solution containing acetic acid was observed, and a solvent-type organic/inorganic hybrid white LED device based on TPBI-BPI was prepared. The luminance efficiency, external quantum efficiency, correlated color temperature, K, and Ra (color rendering index) of the solvent-type WLED are 21.71 lm/W, 12.76%, 6329, and 83.2 at 39.90 mA, respectively. The Commission Internationale de l´Eclairage coordinate of the solvent-type WLED is (0.3135, 0.3507). In addition, the lifetime (T70) of the device can reach 130 h. This is due to the excited state intermolecular proton transfer between TPBI-BPI and acetic acid in ethyl acetate solution after UV illumination. This enables TPBI-BPI to obtain WLE and makes the WLED spectrally stable due to this process's dissipation of UV energy. This work provides a strategy to extend the lifetime of a hybrid LED. [ABSTRACT FROM AUTHOR]

The white light emission arises from a single organic molecule, which is significant for simplifying the device preparation process and obtaining a stable white light spectrum. Unfortunately, white light emission from most single organic molecules is achieved by controlling molecules in the ground or excited state to produce a new generation of luminescent species (complementary color mode). Such newly generated species are difficult to obtain individually. Herein, a new compound named (E)- N , N -diphenyl-4-(4-(1,4,5-triphenyl-1 H -imidazole-2-yl)styryl)aniline (TPASt-PIM) was synthesized in this paper. The organic/inorganic hybrid LED device was prepared by placing TPASt-PIM in silica gel and covering it on a UV chip. A part of TPASt-PIM was used to generate N -((Z)-(benzoylimino)(4-((E)-4-(diphenylamino)styryl)phenyl)methyl)- N -phenylbenzamide (TPASt-PYZ) by photo-oxidation in the device to achieve white light emission. In addition, TPASt-PYZ was prepared and isolated. The mechanism by which TPASt-PIM can emit white light emission in the device was explored. The results show that the photo-oxygenation process of TPASt-PIM in the device can be used to obtain white light emission and achieve energy saving and green utilization because the additional synthesis of TPASt-PYZ is avoided. • A newly developed compound named TPASt-PIM was synthesized. • White light emission was obtained by regulating the degree of open loop of TPASt-PIM involved in the photo-oxidation process. • This work clarifies the structure of open-loop product and explains the mechanism of white light emission. [ABSTRACT FROM AUTHOR]

Aryl-substituted phenanthroimidazoles (PIs) have attracted tremendous attention in the field of organic light-emitting diodes (OLEDs), because they are simple to synthesize and have excellent thermal properties, high photoluminescence quantum yields (PLQYs), and bipolar properties. Herein, a novel blue-green emitting material, ( E)-2-{4′-[2-(anthracen-9-yl)vinyl]-[1,1′-biphenyl]-4-yl}-1-phenyl-1 H-phenanthro[9,10- d]imidazole (APE-PPI), containing a t-APE [1-(9-anthryl)-2-phenylethene] core and a PI moiety was designed and synthesized. Owing to the PI skeleton, APE-PPI possesses high thermal stability and a high PLQY, and the compound exhibits bipolar transporting characteristics, which were identified by single-carrier devices. Nondoped blue-green OLEDs with APE-PPI as the emitting layer show emission at λ=508 nm, a full width at half maximum of 82 nm, a maximum brightness of 9042 cd m−2, a maximum current efficiency of 2.14 cd A−1, and Commission Internationale de L'Eclairage (CIE) coordinates of (0.26, 0.55). Furthermore, a white OLED (WOLED) was fabricated by employing APE-PPI as the blue-green emitting layer and 4-(dicyanomethylene)-2- tert-butyl-6-(1,1,7,7-tetramethyljulolidin-4-yl-vinyl)-4 H-pyran (DCJTB) doped in tris-(8-hydroxyquinolinato)aluminum (Alq3) as the red-green emitting layer. This WOLED exhibited a maximum brightness of 10029 cd m−2, a maximum current efficiency of 16.05 cd A−1, CIE coordinates of (0.47, 0.47), and a color rendering index (CRI) of 85. The high performance of APE-PPI-based devices suggests that the t-APE and PI combination can potentially be used to synthesize efficient electroluminescent materials for WOLEDs. [ABSTRACT FROM AUTHOR]

The deep-blue emitting material 2-(8-(benzyloxy)quinolin-2-yl)-1-phenyl-1 H -phenanthro[9,10- d imidazole (QL-PPI) which contains 8-(Benzyloxy)quinoline core and phenanthroimidazole moiety, has been designed and synthesized. The non-doped OLED using QL-PPI as the emitting layer shows emission at 455 nm, full width at half maximum of 100 nm, maximum brightness of 250 cd m−2, maximum current efficiency of 0.47 cd A−1, and Commission Internationale de L'Eclairage (CIE) coordinate of (0.20, 0.22). Furthermore, the QL-PPI with a slight mass concentration in the silica gel is coated on the near ultraviolet (NUV) chip (380 nm) to prepare the hybrid deep-blue LED device HB1 with a y coordinate = 0.0541. The hybrid WLED device HW1 based on QL-PPI mixed with green phosphor [(Ba, Sr) 2 SiO 4 : Eu2+ and red phosphor [(Sr, Ca) 2 AlSiN 3 : Eu2+ is prepared. The hybrid WLED exhibits luminance efficiency of 18.05 lm W−1 (at 19.90 mA), Correlated Color Temperature (CCT) of 4580 K, Color Rendering Index (CRI) of 80, and CIE chromaticity coordinate of (0.3571, 0.3562). These results reveal that the QL-PPI can apply both in OLED and the hybrid LED simultaneously. The QL-PPI which used in the hybrid WLED has the potential to reduce reliance on rare-earth metals and improve the CRI of the hybrid WLED. • A novel quinoline derivative (QL-PPI) was firstly designed and synthesized. • The QL-PPI possesses high thermal stability and PLQYs. • The QL-PPI can apply both in OLED and the hybrid LED simultaneously. • The CIE of hybrid deep-blue LED device based on QL-PPI is (0.1620, 0.0541). • The QL-PPI applied in the hybrid WLED can reduce reliance on rare-earth metals. [ABSTRACT FROM AUTHOR]