Improved Efficiency of Single‐Layer Polymer Light‐Emitting Devices with Poly(vinylcarbazole) Doubly Doped with Phosphorescent and Fluorescent Dyes as the Emitting Layer

作者：Shihai Kan, Xun Liu, Fengge Shen, Junhu Zhang, Yuguang Ma, G. Zhang, Y. Wang, Jiacong Shen · 发表于：Advanced Functional Materials · 年份：2003 · DOI：10.1002/adfm.200304304 · 被引用次数：47 · 研究领域：Organic Light-Emitting Diodes Research、Luminescence and Fluorescent Materials、Catalytic Cross-Coupling Reactions

Abstract We demonstrate novel organic light‐emitting diode (LED) materials that contain a green phosphorescent dye (dmbpy)Re(CO) 3 Cl (dmbpy = 4,4′‐dimethyl‐2,2′‐bipyridine), and a red fluorescent dye 4‐dicyanomethylene‐6‐( p ‐dimethylaminostyryl)‐2‐methyl‐4H‐pyran (DCM) as dopants and polyvinylcarbazole (PVK) as the host. The photoluminescence (PL) and electroluminescence (EL) properties of these complex materials were studied. The energy transfer efficiency from PVK host to DCM is increased by the (dmbpy)Re(CO) 3 Cl co‐dopant, which has an emission energy between that of PVK and DCM. The (dmbpy)Re(CO) 3 Cl, which emits a long‐lived phosphorescence, is used as an energy coupler, providing the possibility to harvest both singlet and triplet energy in the devices. The pure red emission from DCM was observed from PL and EL spectra of (dmbpy)Re(CO) 3 ‐Cl(> 2.0 wt.‐%):DCM(> 0.5 wt. %) doped PVK films, demonstrating an efficient energy transfer from PVK and (dmbpy)Re(CO) 3 ‐Cl to DCM. By optimizing the concentration of DCM and (dmbpy)Re(CO) 3 Cl in PVK, a maximum EL quantum efficiency of 0.42 cd A –1 at a current density of 9.5 mA cm –2 was obtained. The EL quantum efficiency of the doubly doped device is significantly enhanced in comparison with both a DCM‐only doped PVK device and a DCM‐doped PVK device with the green fluorescent dye Alq 3 as co‐dopant. The improvement in the operating characteristics of the phosphorescent and fluorescent dye doubly doped device is attribu...