خواص فوتوفيزيكي كمپلكس‌هاي پلاتين (II) و برخي تركيبات آلي و بررسي كاربردي آن‌ها در ديودهاي نورگسيل آلي

Photophysical properties of Pt (II) complexes an‎d organic compounds with applications in OLED devices

شيمي فيزيك

Abstract In this study, the photophysical an‎d optoelectronic properties of different organic an‎d inorganic compounds have been investigated with a focus on emission mechanisms, phosphorescence, an‎d singlet–triplet inversion (IST), using density functional theory (DFT), time-dependent DFT (TD-DFT), an‎d ab initio quantum chemical methods to assess their potential applicability in organic light-emitting diodes (OLEDs). In the first sections, two series of platinum (II) complexes based on bidentate 2-phenylpyridine (ppy) an‎d 7,8-benzoquinoline (bzq) ligan‎ds have been examined. Structural analysis revealed that these complexes maintain good geometric stability in the lowest triplet excited state (T1), an‎d minor coordinate changes upon excitation minimize nonradiative energy loss. Simulated absorption spectra indicate that the electronic transitions are primarily of MLCT, ILCT, an‎d LLCT character an‎d show good agreement with experimental data. Analysis of the HOMO an‎d LUMO orbitals demonstrate that their electron density distribution an‎d proper overlap optimize charge transfer pathways an‎d carrier mobility. Regarding emission, the phosphorescence spectra have been predicted in the green-to-red region, with the dominant transitions in most complexes being ³MLCT/³ILCT. High spin–orbit coupling (SOC) values an‎d suitable singlet–triplet energy gaps facilitate intersystem crossing (ISC) an‎d enhance phosphorescence quantum yields. These features, together with the favorable alignment of the complexes’ energy levels with common OLED materials, provide ideal conditions for efficient charge transport an‎d suppression of energy back-transfer, highlighting the high potential of these complexes for high-efficiency OLED applications. In the third section, new frameworks based on polycyclic aromatic hydrocarbons (PAHs) with targeted boron–nitrogen (B–N) substitution have been designed an‎d analyzed. High-level calculations (ADC(2), CC2, CASPT2, an‎d TD-DFT) showed that incorporating triangularly arranged B–N units not only preserve singlet–triplet inversion (IST) but also enhances it, reducing the ΔST gap in some cases to –0.29 eV. The decrease in HOMO–LUMO overlap an‎d the reduction of the exchange integral (KHL) were identified as key factors in stabilizing an‎d reinforcing IST. Furthermore, the SOS-RSX-QIDH functional was introduced as a precise an‎d reliable tool for predicting IST behavior, showing excellent agreement with wavefunction-based methods.

5

151717