DFT/TD-DFT study of electronic and phosphorescent properties in cycloplatinated complexes: implications for OLEDs

Abstract

High level density functional and time-dependent density functional (DFT, TD-DFT) theoretical methods have been employed to investigate the photophysical properties of 5 inorganic compounds resulting from Pt(ii) and ppy (2-phenyl-pyridine) ligands.

Photophysical properties of Pt(ii) complexes based on the benzoquinoline (bzq) ligand with OLED implication: a theoretical study

“…In this study, the density functional theory (DFT) and the timedependent density functional theory (TD-DFT) based on the B3LYP functional [29][30][31] were employed to determine the ground and excited state properties, respectively. This methodology has been widely used 10,11,[32][33][34][35] in studying the different aspects of organic and inorganic systems such as electronic structures, [36][37][38] excited-state properties, [39][40][41] and also OLED devices. [42][43][44][45][46] Thus, the ground and excited states of selected systems were optimized, and the required photophysical parameters were determined.…”

“…It is known that a lower IP facilitates hole injection, while a higher EA facilitates electron injection. 10,20,60 Also, the charge transfer character can be related to the spatial distribution of HOMO and LUMO orbitals. The IP and EA values are closely related to the energies of HOMO and LUMO, respectively.…”

“…7 In recent years, research on the development of OLED devices has focused on two aspects: color improvement, quantum efficiency through doping heavy metal complexes, and optimizing the structure of devices. In this regard, extensive efforts have been made to study heavy metal complexes, including platinum(II), [8][9][10][11] iridium(III), [12][13][14] and ruthenium(I), 15,16 with their impact on OLED systems. Also, choosing the appropriate host and guest materials in the emissive layer is another important strategy to optimize the structure of these devices.…”

“…17 Recent studies have shown that more exciton generation would lead to a higher efficiency in the OLED devices. 18,19 Platinum(II) 9,10,[20][21][22] complexes are widely used as guest materials in the structure of OLEDs. These compounds, having the conguration of d 8 electrons, exhibit a square-planar structure.…”

“…These cyclometalated platinum complexes have been previously reported to be quite promising for OLED devices. 10,20,23 In this study, we have investigated the photophysics and optoelectronic properties of eight cycloplatinated complexes as candidates to be suggested for use in OLED devices (see Fig. 1).…”