Exciton behaviours in doped tris (8‐hydroxyquinoline) aluminum (Alq₃) films

Abstract

The doping effect on exciton behaviours in amorphous tris (8‐hydroxyquinolinato) aluminum (Alq3) were studied for the first time by transient photoluminescence (PL) measurements at room temperature. The dopants 4‐(diacynomethylene)‐2‐methyl‐6‐(p‐dimethylaminostyryl)‐4H‐pyan (DCM) and 5,6,11,12‐tetraphenylnaphthacene (rubrene) were used into Alq3 films at various concentration from 0.5 to 24 wt.% for this study. The exciton recombination rate was found sharply increased with doping concentration in Alq3 films. The exciton lifetime in pure Alq3 was found as ∼ 20 ns and it was reduced up to ∼8 ns with doping concentration. The exciton diffusion coefficient and diffusion length in doped films was found as 0.5 – 1.4 × 10–6 cm2 s–1 and 18–35 Å, respectively (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Solid-State Solvation and Enhanced Exciton Diffusion in Doped Organic Thin Films under Mechanical Pressure

“…The corresponding fitted luminescence lifetimes are within 0.2 ns for the measured range of pressures. This is in contrast to previous time-resolved DCM doping PL studies, where the lifetime significantly decreased with increased DCM concentration, due to the exciton quenching by aggregated dye molecules. This comparison highlights that the solvatochromic shift due to change in density in organic matrix under pressure does not exhibit the pronounced aggregation quenching effect on exciton lifetime.…”

Bilayer-structure white organic light-emitting diode based on [Alq3:rubrene] and the electron transporting characteristics investigation using impedance spectroscopy

“…The early works show that rubrene promotes electron transporting in [Alq 3 :(coumarin 6, rubrene)] (Alq 3 co-doped with coumarin 6 and rubrene) [10]. In [Alq 3 :rubrene], it was also found that rubrene promotes excimer diffusion coefficient but decreases diffusion length and life-time [11]. In this study, our results indicate that rubrene doping in Alq 3 slightly impedes electron transporting.…”

“…This bilayer-structure WOLED shows quite simple configuration of ITO/ hole-injection layer/ hole-transport-and-blue-emitting layer (HT-BEML)/electron-transportand-yellow-green-emitting layer (ET-YEML)/electron-injection layer/ cathode. 5,6,11,12-tetraphenylnaphthacene (rubrene) doped tris(8-hydroxy-quinolinato)aluminum (Alq 3 ), [Alq 3 :rubrene], is one of the most widely-used yellow-green emitter for its excellent emitting efficiency and film morphology [9][10][11][12]. Consequently, the electron transporting characteristics play a crucial role in bilayer-structure WOLED with [Alq 3 :rubrene] as ET-YEML.…”