Exploring Acceptor-Functionalized Perylenes as Hole Transport Materials for Solution Process Organic Light-Emitting Diodes

Abstract

The high charge carrier mobility and organized solid-state structure of perylene-based materials enable them to be used in optoelectronics. The impressive luminance of organic lightemitting diodes (OLEDs) helps in improving visibility for both indoor and outdoor activities. Considering the good charge mobility of the perylene-based structures, we report perylenebased three molecular systems viz. PhPrPy, AnPrPy, and TPAPrPy, integrated with functionalized pyridines, leading to the formation of donor−acceptor (D−A) systems which were finally explored as hole transport materials (HTMs) for solution-process OLEDs. The pyridine units were functionalized with phenyl, pmethoxyphenyl, and triphenylamine functionalities. For theoretical screening, density functional theory was adopted for evaluating the molecules for their optimized geometries, highest occupied molecular orbital/lowest unoccupied molecular orbital energy levels, reorganization energies, and hole and electron distribution in the excited states. The theoretical reorganization energies and ionization potentials indicated their possible capability for hole transportation. The theoretical studies revealed that the incorporation of a triphenylamine unit in the molecular framework significantly reduced the hole reorganization energy. Based on theoretical predictions, we chose TPAPrPy as the most promising one for solution-process device fabrication. The fabricated green phosphorescent OLED with TPAPrPy as HTM showed good performance with power efficacy (PE), current efficacy (CE), and external quantum efficiency (EQE) of ∼77 lm/W, ∼78 cd/A and ∼22%, respectively. Given the PE, CE, and EQE of the present device, the important outcome of using TPAPrPy as HTM was a good balance between PE, CE, and EQE with a low trade-off.Importantly, low roll-off in PE, CE, and EQE was observed when measured at a brightness of 100 and 1000 cd/m 2 .