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To find an array of suitable materials for phosphorescent organic light‐emitting diodes (OLEDs), in this paper, we design six blue‐green phosphorescent Ir (III) complexes that have low‐efficiency roll‐off properties. Density functional theory and time‐dependent density functional theory were used to study the properties of (2‐[4‐phenoxyphenyl]pyridine [oppy])2Ir(acetylacetonate [acac]), (oppy)2Ir(picolinate [pic]), (oppy)2Ir(tetraphenylimido‐diphosphinate [tpip]), (5‐fluoro‐2‐(4‐phenoxyphenyl)pyridine [F‐oppy])2Ir(acac), (F‐oppy)2Ir(pic), and (F‐oppy)2Ir(tpip). Here, the main ligands are oppy and F‐oppy, while the auxiliary ligands are acac, pic, and tpip. The advantages of these complexes were analyzed in terms of electronic structure, frontier molecular orbital properties, spectral properties, and OLED display effect. We hope that our research will contribute to the development of the OLED industry. [ABSTRACT FROM AUTHOR]

Here six phosphorescent heteroleptic cyclometalated Ir (III) complexes were theoretically designed to identify some suitable OLED materials. (fppzb)2Ir(acac), (fppzb)2Ir(tpip), (dfbdp)2Ir(fppzb), (F-fppzb)2Ir(acac), (F-fppzb)2Ir(tpip), and (dfbdp)2Ir(F-fppzb) were studied via density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. Here, acac denotes acetylacetonate, tpip denotes tetraphenylimido-diphosphinate, fppzb denotes 4-tert-butyl-2-(5-(trifluoromethyl)-4H-pyrazol-3-yl) pyridine and F-fppzb denotes 4-tert-butyl-2-(5-fluoro-4H-pyrazol-3-yl) pyridine. Further, we discuss the value of these materials from the electronic structure, spectral properties, ionisation potentials, electron affinities, and application prospects of the complexes. We hope that these light-emitting materials contribute to the OLED sector. This theoretical study included the energy transfer mechanism of the complexes with acac and tpip substituents as auxiliary ligands: We analyzed the possibilities and inevitability of the results in the experiments as well as evaluated the underlying mechanism for these materials' low-efficiency roll-off. [ABSTRACT FROM AUTHOR]

The present paper mainly studies the influence of the junction temperature on the white LED spectral characteristics of the mixture of the DCJTB and YAG: Ce3+ phosphor. With layered coating of YAG phosphor and organic materials DCJTB on the LED chip with the method of hierarchical point powder, the color rendering index of the device will reach up to 90. The junction temperature can be measured conveniently and accurately with the integrated LED cooling pad which was developed by the laboratory. Experiments show that: the rise of the junction temperature can make the radiation amplitude of the blue chip decline continuously. The yellow radiation amplitude of YAG phosphor which is excited by radiation first increases and then decreases, the red spectrum is blue-shifted, the color rendering index of the device decreased linearly, while the color temperature first increases and then decreases.