White-emitting organic diode with a doped blocking layer between hole- and electron-transporting layers

Abstract

A new white-emitting organic diode was realized simply by inserting a doped hole-blocking layer between the hole-transporting layer (HTL) and the electron-transporting layer (ETL). The structure of this device is ITO/CuPc/NPB/blocking layer:rubrene/Alq/MgAg. Copper phthalocyanine (CuPc) was used as a buffer layer; N,N -bis-(1-naphthyl)-N,N -diphenyl-1.1 -biphenyl-4-4 -diamine (NPB) was the HTL; the tris(8-quinolinolato)aluminium complex (Alq) was the ETL; and the trimer of N-arylbenzimidazole (TPBi), 2-(4-biphenylyl-5-(4-tertbutylphenyl)-1,2,3-oxadiazole (PBD) or the 1,2,4-triazole derivative (TAZ) were used as the blocking layers, in which rubrene is doped. The emission spectrum of this device covers a wide range of the visible region and can be sensitively adjusted by the concentration of rubrene. The white emission with CIE (Commission International de l'Eclairage) coordinates x = 0.31, y = 0.32, a maximum luminance of 8635 cd m −2 and maximum luminous efficiency 1.39 lm w −1 (4.9 V) were obtained in the device with a concentration of 1.5% rubrene in TPBi.

New Trends in the Use of Transition Metal–Ligand Complexes for Applications in Electroluminescent Devices

“…Usually bathocuproine (BCP) [13,19,22,48,49] and (biphenyloxolatoaluminum(III) bis[2-methylquinolinato(phenylphenolate)] (BAlq) [65,73] are used as HBL or exciton-blocking layers. Other compounds, such as fluorinated phenylenes [51] and oxadiazole, as well as triazolecontaining molecules such as the trimer of N-arylbenzimidazoles (TPBi), [74,75] 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole (PBD), [24] 3-phenyl-4-(1¢-naphthyl)-5-phenyl-1,2,4-triazole (TAZ), [76,77] 1,8-naphthalimides, [78] polyquinolines, [79] or carbon nanotubes doped in PPV [80] were also found to be useful as HBLs. In the last step, depositing a cathode completes the assembly of the device.…”

Triplet Harvesting in Hybrid White Organic Light‐Emitting Diodes

“…[6] The molecular concentration of each dye had to be carefully adjusted to balance Förster transfer and achieve white emission. [7] Better control of sequential energy transfer was achieved with separate emission layers [8][9][10] and additional interlayers. [11,12] Various phosphorescent dyes were used in white OLEDs to boost the efficiency, which requires additional care to be taken for energy transfer by triplet exciton diffusion.…”

White organic electroluminescent devices

“…Moreover, the HBL can be enhanced by an advanced framework ( Fig. 1) [6,7], which does not need to modify the thickness of the HBL to penetrate through the holes, and which obtains yellow-red light directly from HBL. Although this framework cannot emit primary colors (R, G, B), it generates perfect white light through a complement of blue and yellow-red light.…”