Luminescence Characteristics of Blue Emission Phosphorescent Material Firpic

Abstract

The luminescent properties of bis[(4,6-difluorophenyl)-pyridinato-N,Cʹ]c(picolinate)iridium(III) (FIrpic) dependence on the doping concentrations and different annealing treatments were investigated. The color of emission from thin films and organic light emitting diodes (OELDs) could be adjusted from blue to yellow-green by controlling the FIrpic doping concentration. There was good spectral overlap from 440 to 480 nm between the FIrpic photoluminescence (PL) spectra and its absorption spectra. The 476 nm emission intensity decreased as the FIrpic doping concentration increased, and this effect could be attributed to FIrpic self-absorption. The PL and electroluminescence (EL) spectra were measured under different excitation power densities and in different doping concentrations, respectively. The intensity of emission peak at 530 nm was enhanced as the excitation power density or FIrpic doping concentration increased. This suggests that the emission peak at 530 nm originates from the excimer emission between FIrpic molecules. The morphologies of the thin film and changes in the EL spectra were analyzed before and after annealing treatment. This demonstrated that FIrpic molecular aggregation promoted by annealing [Article] www.whxb.pku.edu.cn 物理化学学报(Wuli Huaxue Xuebao) Acta Phys. -Chim. Sin. 2012, 28 (4), 949-956 April Received: November 23, 2011; Revised: January 5, 2012; Published on Web: January 16, 2012. ∗Corresponding author. Email: fjzhang@bjtu.edu.cn; Tel: +86-10-51684908. The project was supported by the National Key Basic Research Program of China (973) (2010CB327704), National Natural Science Foundation of China (10804006, 60576016), National Outstanding Young Scientists Foundation of China (60825407), Natural Science Foundation of Beijing, China (1102028), Program of Introducing Talents of Discipline to Universities, China (B08002), Fundamental Research Funds for the Central Universities, China (2011JBM123, 2010JBZ003), and Talent Plan of Red Berry of Beijing Jiaotong University, China. 国家重点基础研究发展规划(973) (2010CB327704),国家自然科学基金(10804006, 60576016),国家杰出青年基金(60825407),北京市自然科学 基金(1102028),高等学校学科创新引智计划(B08002),高等学校基本科研业务基金(2011JBM123, 2010JBZ003)及北京交通大学红果园人才计 划资助 C Editorial office of Acta Physico-Chimica Sinica doi: 10.3866/PKU.WHXB201201163 949 Acta Phys. ⁃Chim. Sin. 2012 Vol.28 treatment could increase the intensity of excimer emission between FIrpic molecules. The emission color of OLEDs could be adjusted from blue to yellow-green by changing the FIrpic doping concentration, optimizing the device structure, and using annealing treatment on the devices.