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Abstract: A high-efficiency, undoped, blue, organic light-emitting device was devised that employed a novel electroluminescent material 4-(7,10-diphenylfluoranthen-8-yl)-N,N-diphenylbenzenamine as electrofluorescence emitter. The device with a simple structure of ITO/N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine/4-(7,10-diphenylfluoranthen-8-yl)-N,N-diphenylbenzenamine/4,7-diphenyl-1,10-phenanthroline/LiF/Al exhibited stable blue light emission of CIE chromaticity coordinates (x =0.19±0.01 and y =0.45±0.02), and a current efficiency of 6.0cd A−1 and a power efficiency of 4.6lm W−1. [Copyright &y& Elsevier]

Abstract Deep blue emitters with good stability, high quantum yield, high triplet energy, and good carrier transporting properties are crucial for full color display and white solid lighting. To solve this, We designed, synthesized and characterized two bipolar deep-blue emitters 2-(4-(9,9′-spirobi[fluoren]-2-yl)phenyl)-1-phenyl-1H-phenanthro[9,10-d]imidazole (2-PPI SBF) and 2-(4-(9,9′-spirobi[fluoren]-4-yl)phenyl)-1-phenyl-1H-phenanthro[9,10-d]imidazole (4-PPI SBF). Both the materials show good stability, high quantum yield and high triplet energy. Equipped with their bipolar properties, 2-PPI SBF and 4-PPI SBF based non-doped devices show impressive performance with maximum external quantum efficiency (EQE) of 4.78% and 5.29% along with desirable color purity of CIE color coordinates of (0.154, 0.105) and (0.155, 0.058) respectively. Interestingly, the high triplet energy allows them to be used as a host for PhOLEDs. High performance green PhOLEDs based on 4-PPI SBF show the maximum EQE, CE and PE of 16.79%, 64.09 cd/A and 67.92 l m/W respectively. And, high performance red PhOLEDs based on 2-PPI SBF and 4-PPI SBF were also achieved with the maximum EQE of 13.07% and 14.83%, respectively. Furthermore, 4-PPI SBF-based WOLED shows high efficiencies with EQE max of 12.27%, CE max of 27.78 cd/A and PE max of 32.68 l m/W. An efficient white OLED with CIE coordinates of (0.367, 0.305) which is slightly deviated from the values of the theoretical white point (0.33, 0.33) was obtained. Graphical abstract Image 1 Highlights • Two deep-blue bipolar universal materials were designed and synthesized. • Non-doped blue OLED based on 2-PPI-SBF and 4-PPI-SBF achieved EQE up to 4.78% and 5.29%, respectively. • The red PhOLEDs using 4-PPI-SBF as host achieved the maximum EQE of 14.83%. [ABSTRACT FROM AUTHOR]

To increase the fluorescence quantum yield of hybrid local and charge-transfer (HLCT) material, we introduce a symmetric linear D- π -A- π -D structure into molecular design and synthesized a new blue emitter, 2,2'-(2′,3′,5′,6'-tetrafluoro-[1,1':4′,1″-terphenyl]-4,4″-diyl)bis(1-(4-( tert -butyl)phenyl)-1 H -phenanthro[9,10- d ]imidazole) ( 4FBTPI ). Organic light-emitting devices employing 4FBTPI as a dopant emitter show good performances, with CIE (Commission Internationale de l’Enclairage) coordinates of (0.15, 0.09), which is very close to NTSC blue light standard (0.14, 0.08), current efficiencies (CE) of 6.03 cd A −1 , external quantum efficiencies of 6.94%. This performance is comparable to those of recently reported state-of-the-art deep-blue materials with CIE y < 0.10. [ABSTRACT FROM AUTHOR]

A novel near ultraviolet (NUV) emitter, PIBCz, was designed and synthesized by attaching C3-position of the weak electron-donating N-phenylcarbazole group to C6- and C9-positions of phenanthroimidazole (PI) unit for limiting the molecular conjugation and intramolecular charge transfer (ICT) process. The new emitter exhibits strong NUV emission both in solution and thin film as well as good thermal and morphological stability. The PIBCz-based non-doped device shows a perfect color purity of CIE (0.15, 0.05), a very low turn-on voltage of 2.7 V and a maximum external quantum efficiency (EQE), current efficiency (CE) and power efficiency (PE) of 2.74%, 1.28 cd A −1 and 1.12 lm W −1 , respectively, which is comparable to state-of-the-art non-doped OLEDs in similar color gamut. This work demonstrates that effective management of ICT process is a valuable strategy to develop high efficiency NUV emitters. [ABSTRACT FROM AUTHOR]

Abstract: We report a newly synthesized blue fluorescent pyrene-phenanthroimidazole based emitter Py-BPI and its applications in non-doped organic light-emitting devices (OLEDs). Py-BPI has a high fluorescence quantum yield of 40% and good thermal stability with a high glass transition temperature of 137 °C. Based on Py-BPI, OLEDs with several configurations have been fabricated. Among these devices, an OLED with only two organic layers of Py-BPI and BPhen demonstrates blue emission with high efficiencies of 3.93 cd/A and 3.2 lm/W and maintains a high efficiency of 3.83 cd/A even at a brightness of 5000 cd/m2. Combining with its hole-transporting ability, Py-BPI is shown to be a versatile blue emitter especially suitable for high brightness applications. [Copyright &y& Elsevier]

Charge balance does matter for emission materials to obtain high-performance organic light-emitting diodes (OLEDs), and it is well-known that the electron-transporting ability is inferior to the hole-transporting for the majority of organic emitting materials, especially for blue-emitting compounds. Hence, systematically investigating the effect of the electron-withdrawing group on fluorophore is of vital importance. In this study, we designed and synthesized two deep-blue phenanthro[9,10-d]imidazole (PI) based materials named DPy-PPI and DmPy-PPI by using pyridine-containing groups as electron acceptor as well as adjusting the conjugation length. The photophysical, theoretical, thermal and electrochemical properties of the compounds were investigated systematically, and the relationship between the conjugation length of substituent groups on phenanthroimidazole and the EL performance was clarified. Both of them exhibited good thermal stability and high photoluminescence quantum yields. Non-doped devices based on DPy-PPI and DmPy-PPI as emitter achieved deep-blue emissions with the Commission Internationale de L'Eclairage (CIE) index of (0.14, 0.06) and (0.15, 0.08) and high external quantum efficiencies (EQE max) of 4.24% and 3.74%, respectively. Meanwhile, using DPy-PPI and DmPy-PPI as the host materials, yellow-orange phosphorescent organic light-emitting diodes (PHOLEDs) were fabricated with EQE max , CE max and PE max of 20.55%, 63.86 cd/A, 37.08 lm/W and 18.14%, 55.84 cd/A, 32.47 lm/W, respectively. Furthermore, the red PHOLEDs were also constructed using DPy-PPI and DmPy-PPI as the host with EQE max , CE max and PE max of 14.53%, 17.04 cd/A, 18.51 lm/W and 16.62%, 23.58 cd/A, 21.16 lm/W, respectively. And we believe this work can provide some insight suggestions for scientific researchers to design deep-blue emitting materials. Two deep-blue emitters were constructed by using pyridine group as acceptor. The non-doped device, yellow-orange and red PhOLEDs were fabricated. Image 1 • Non-doped deep blue OLED based on DPy-PPI as emitter was achieved with EQE of 4.24% and CIE coordinates of (0.14, 0.06). • DPy-PPI and DmPy-PPI are the efficient host materials for yellow-orange and red PHOLEDs. • DPy-PPI have more balanced carrier transporting ability than DmPy-PPI. • DPy-PPI and DmPy-PPI have good thermal stability and high photoluminescence quantum yields. [ABSTRACT FROM AUTHOR]