Deep Blue Exciplex Organic Light‐Emitting Diodes with Enhanced Efficiency; P‐type or E‐type Triplet Conversion to Singlet Excitons?

Abstract

Simple trilayer, deep blue, fluorescent exciplex organic light‐emitting diodes (OLEDs) are reported. These OLEDs emit from an exciplex state formed between the highest occupied molecular orbital (HOMO) of N,N′‐bis(1‐naphthyl)N,N′‐diphenyl‐1,1′‐biphenyl‐4,4′‐diamine (NPB) and lowest unoccupied molecular orbital (LUMO) of 1,3,5‐tri(1‐phenyl‐1H‐benzo[d]imidazol‐2‐yl)phenyl (TPBi) and the NPB singlet manifold, yielding 2.7% external quantum efficiency at 450 nm. It is shown that the majority of the delayed emission in electroluminescence arises from P‐type triplet fusion at NPB sites not E‐type reverse intersystem crossing because of the presence of the NPB triplet state acting as a deep trap.

Singlet Generation from Triplet Excitons in Fluorescent Organic Light-Emitting Diodes

“…The exciplex has a PLQY of 26% and EQE of 2.6% (unoptimized) at 450 nm. For this low PLQY of the emitter, the theoretical maximum device EQE is 1.3% [148]. However, in this exciplex system the D (NPB) has a triplet level [149] lower than that of the exciplex triplet which we believe strongly quenches the exciplex triplet state, but the subsequent high triplet population gives rise to strong TF which enhances the device efficiency.…”

Light-Emitting Devices – Luminescence from Low-Dimensional Nanostructures

“…However, we have overcome this problem by using ammonium chloride (NH 4 Cl). The addition of NH 4 Cl to the starting Al powder produced many pores because of the decomposition of NH 4 Cl [52][53][54]. Therefore, the introduction of porosity during the synthesis can enhance the nitridation rate because N 2 gas easily has more access to the pores, which causes the formation of nanostructures AlN powders with low agglomeration.…”

“…al [2] and led researchers to investigate organic materials as light-emitting devices [3][4][5][6]. The working principles of these devices are similar to normal LEDs with the difference that an organic compound is used as an emissive layer.…”

Determination of standard redox rate constants of OLED active compounds by electrochemical impedance spectroscopy

“…9H-carbazole (CzSi) mostly to show the usefulness of the method. These compounds were chosen because they take an active part in intermolecular exciplex formation (Table 1) [10,12,14,15]. [19] 5…”