High-efficiency and long-lifetime solution-processed red PHOLEDs using n-type host materials and an Ir(III) complex

Abstract

High-performance solution-processed red phosphorescent organic light-emitting diodes (PHOLEDs) are required to reduce energy consumption and fabrication costs. However, solution-processed red PHOLEDs have low performance and short operating lifetimes. We designed and synthesized a red phosphor and two n-type hosts to achieve highly efficient solution-processed red PHOLEDs. The developed red phosphor, Red12 has high thermal stability and a photoluminescence quantum yield of exceeding 95%. Naphthalene-based n-type host materials, namely 2-(4-(naphthalen-1-yl)phenyl)-4,6-diphenyl-1,3,5-triazine (DPTPN) and 2-(4-(2-methylnaphthalen-1-yl) phenyl)-4,6-diphenyl-1,3,5-triazine (DPTPMN) have a suitable LUMO energy level, high charge carrier mobility, and excellent thermal stability. In particular, the matched LUMO levels between DPTPN and the red dopant minimized charge trapping and exciton quenching, leading to improved device efficiency and operational stability. The optimized red PHOLEDs based on DPTPN or DPTPMN exhibited maximum external quantum efficiencies of 29.5 and 28.9%, current efficiencies of 43.1 and 42.5 cd/A, and power efficiencies of 33.8 and 33.4 lm/W, respectively. Furthermore, a device with a TCTA:DPTPN:Red12 emitting layer had a 50-fold greater lifetime than TCTA:TPBi:Red12.