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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]

This study employs density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT) to investigate a series of cyclometallated Ir(III) complexes for their application as OLED light‐emitting materials, including (dtp)2Ir(dpm), (mmpyp)2Ir(dpm), (dtp)2Ir(tpip), (mmpyp)2Ir(tpip), (dtp)2Ir(pic), and (mmpyp)2Ir(pic). Their geometries, frontier molecular orbital properties, ionization potential, electron affinity, absorption and emission spectra, and spin‐orbit coupling properties have been analyzed respectively. Through comparison, we have identified complexes with reduced efficiency roll‐off and enhanced kISC. [ABSTRACT FROM AUTHOR]

In this paper, several Ir (III) complexes with transition metal as the central atom formed by the corresponding combination of two main ligands and three auxiliary ligands have been studied theoretically. The electronic structure, frontier molecular orbital, and spin orbit coupling data are used to analyze its application value in light emitting devices. The density functional theory is used to study (tbi)2Ir(bpp), (tbi‐c)2Ir(bpp), (tbi)2Ir(dbm), (tbi‐c)2Ir(dbm), (tbi)2Ir(pic), and (tbi‐c)2Ir(pic). bpp = (2Z)‐3‐hydroxy‐13‐diphenylprop‐2‐en‐1‐one; dbm = 1,3‐di‐phenyl‐1, 3‐propanedione; pic = picolinate. [ABSTRACT FROM AUTHOR]

Here, eight phosphorescent heteroleptic cyclometalated Ir (III) complexes were theoretically designed to identify some suitable organic light‐emitting diode materials. (F2‐PYBPY)2Ir (acac) (marked 1), (F2‐PYBPY)2Ir (tpip) (marked 2), (PYBPY)2Ir (acac) (marked 3), (PYBPY)2Ir (tpip) (marked 4), (F2‐PYPY)2Ir (acac) (marked 5), (F2‐PYPY)2Ir (tpip) (marked 6), (PYPY)2Ir (acac) (marked 7), and (PYPY)2Ir (tpip) (marked 8) were studied via density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT) methods. Here, acac denotes acetylacetonate, tpip denotes tetraphenylimido‐diphosphinate, F2‐PYBPY denotes 3‐(4‐tert‐butylpyridin‐2‐yl)‐2,6‐difluoropyridine, PYBPY denotes 4‐tert‐butyl‐2‐(pyridin‐3‐yl) pyridine, F2‐PYPY denotes 2,6‐difluoro‐3‐(pyridin‐2‐yl) pyridine, and PYPY denotes 2‐(pyridin‐3‐yl) pyridine. Further, we discuss the value of these materials from the electronic structure, spectral properties, ionization potentials, electron affinities, and application prospects of the complexes. We hope that these light‐emitting materials contribute to the organic light‐emitting diode 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]

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]

Complete active space self-consistent field (CASSCF) and multiconfiguration second-order perturbation theory (CASPT2) calculations with contracted ANO-RCC basis set were performed for low-lying electronic states of CH3SS and its cation in Cs symmetry. For the ground state X2A″ of CH3SS, the calculated S-S stretching mode is in good agreement with experimental reports. The electron transitions of CH3SS+, X1A′ → 11A″, X1A′ → 21A′, and X1A′ → 21A″, are predicted at 1.055, 3.247, and 3.841 eV. Moreover, the calculated adiabatic and vertical ionization potential and adiabatic affinity are in reasonable agreement with the experimental data. The CASSCF/CASPT2 potential energy curves (PECs) were calculated for S2-loss dissociation from the X2A″, 12A′, and 22A″ states. The electronic states of the CH3 radical and S2 molecule as the dissociation products were carefully determined by checking energies and geometries of the asymptote products. The S2-loss PEC for CH3SS indicate that S2-loss dissociation occurs from the X2A″ state leading to CH3 (12A″) + S2 (X3Σ [ABSTRACT FROM AUTHOR]

A series of heteroleptic cyclometalated Ir (III) complexes with low‐color‐temperature and low‐efficiency roll‐off properties, which cause a fast reduction in efficiency when the drive current increases, for organic light‐emitting devices are investigated theoretically to explore their electronic structures and spectroscopic properties. The geometries, electronic structures, lowest‐lying singlet absorptions and triplet emissions of (ptpy)2Ir(acac), and the theoretically designed models (ptpy)2Ir(tpip), (F‐ptpy)2Ir(acac), (F‐ptpy)2Ir(tpip), (F2‐ptpy)2Ir(acac) and (F2‐ptpy)2Ir(tpip), are investigated with density functional theory approaches, where ptpy denotes 4‐phenylthieno [3,2‐c] pyridine, acac denotes acetylacetonate, tpip denotes tetraphenylimido‐diphosphinate, F‐ptpy denotes 4‐(3‐fluorophenyl) thieno [3,2‐c] pyridine, and F2‐ptpy denotes 4‐(2,4‐difluorophenyl) thieno [3,2‐c] pyridine. A series of heteroleptic cyclometalated Ir (III) complexes, which are used for OLED application, were investigated by DFT and TD‐DFT method. The frontier molecular orbital character and charge transfer character show that they have the advantages of low‐efficiency roll‐off and low‐color‐temperature properties, which is a 'stumbling block' in the process of OLED solid‐lighting's development. This means that the materials play an important role in the development of OLED. [ABSTRACT FROM AUTHOR]

The luminescence characteristics of small molecule excited B 40 have not been studied yet, and it may have a potential application value in quantum dot luminescence. Herein, the adsorption and fluorescence emission spectra of small molecules (pyridine, pyrazine and benzene) adsorbed on B 40 are studied using first-principles. The results show that the absorption of pyridine and pyrazine on B 40 can form stable chemisorption structures pyridine-B 40 and pyrazine-B 40 , while benzene adsorption can form physisorption structure benzene-B 40 . Moreover, the adsorbed pyridine can enhance the intensity of emission spectra of B 40 . And the pyrazine adsorbed can obviously enhance the intensity of absorption and emission spectra of B 40 and cause the spectra to redshift to the visible light range. And the adsorption of benzene has almost no enhancement effect on absorption and emission spectra of B 40 . In addition, the influence of different computational basis sets on spectra characteristics has also been discussed and the results show that the main peaks of absorption and emission spectra calculated by the diffuse function augmented basis sets are redshifted relatively. This finding provides a strategy for quantum dot luminescence and a theoretical reference for experimental research., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)