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

Abstract

We demonstrate novel organic light‐emitting diode (LED) materials that contain a green phosphorescent dye (dmbpy)Re(CO)3Cl (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)3Cl co‐dopant, which has an emission energy between that of PVK and DCM. The (dmbpy)Re(CO)3Cl, 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)3Cl 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 Alq3 as co‐dopant. The improvement in the operating characteristics of the phosphorescent and fluorescent dye doubly doped device is attributed to efficient energy transfer in the system, in which both triplet and singlet excitons are used for resultant emission in the polymer device.

Recent Progresses on Materials for Electrophosphorescent Organic Light‐Emitting Devices

“…In 2003 Ma and his co-workers [ 126 ] doped green phosphorescent dye (dmbpy)Re(CO) 3 Cl and red fl uorescent dye 4-dicyanomethylene-6-(p-dimethylaminostyryl)-2-methyl-4H-pyran (DCM) into PVK host, where dmbpy is 4,4 ′ -dimenthyl-2,2 ′ -bipyridine and Figure 13 . HT Materials for green PhOLEDs.…”

Synthesis and Characterization of a Multicomponent Rhenium(I) Complex for Application as an OLED Dopant

“…Re I polypyridyl complexes are known to be highly emissive [11,12] and have been used as emitting dopants in a variety of OLED structures. [13][14][15] 1,3,4-Oxadiazole heterocycles are widely used as electron-transporting groups owing to their electron deficiency and good thermal stability. [2] The terthiophene subunit can act as a hole-transport group [16] and can also be easily functionalized and polymerized.…”

Spectral studies of thin films based on poly(N-vinylcarzole) and red dopant

“…Tang's report in 1987 [1][2][3][4][5]. Much progress has been made in improving the efficiency and brightness of the diodes and to realize multicolor or white emission [6][7][8]. Recently, doping of organic lightemitting layers with fluorescent or phosphorescent dyes has become a promising method.…”