A π–D and π–A Exciplex‐Forming Host for High‐Efficiency and Long‐Lifetime Single‐Emissive‐Layer Fluorescent White Organic Light‐Emitting Diodes

Abstract

Emerging materials with thermally activated delayed fluorescence (TADF) have opened a new avenue toward all-fluorescent white organic light-emitting diodes (WOLEDs) that enable the full use of electrically generated excitons with noble-metalfree pure organic materials. [1-2] And thanks to the conceptually improving of TADF emitters and white devices structures,

Hydrogen‐Bond‐Assisted Exciplex Emitters Realizing Improved Efficiencies and Stabilities in Organic Light Emitting Diodes

“…[4][5][6] Compared with single-molecule TADF emitters, exciplex emitters have unique superiorities, such as needlessness of hosts, controllable carriers mobilities, and convenient carriers injections. [7][8][9] Therefore, in recent years, great efforts have been made to improve the performance of exciplex emitters. [10][11][12][13][14][15][16][17] As shown in Figure 1, for the excited states of exciplex emitters (S 1 E and T 1 E ), the radiation process contains two channels, prompt fluorescence from S 1 E and delayed fluorescence through RISC process from T 1 E .…”

Are the rates of dexter transfer in TADF hyperfluorescence systems optically accessible?

“…It is therefore imperative to distinguish which of these two processes (or what proportion of each) contributes to the observed DF lifetime shortening. Indeed, in a recent report 53 similar changes in the DF lifetime have been wholly attributed to DET without sufficient justification. In order to understand the energy transfer processes active in hyperfluorescence films and OLEDs, it is necessary to develop methods that distinguish these two potential effects.…”

“…Instead these changes in rate are two orders larger in the PF than in the DF, observed both here and by others. 9,53 The absence of any appreciable PLQE quenching at intermediate FE concentrations (and the lack of FE transient absorption signal) simultaneously indicate that DET is not active in optical measurements.…”

Hyperfluorescent polymers enabled by through-space charge transfer polystyrene sensitizers for high-efficiency and full-color electroluminescence

“…Hyperfluorescence, also termed as "TADF-sensitized fluorescence", has been developed as an attractive strategy for high-efficiency small-molecule OLEDs by vacuum deposition in last couple of years. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] In this motif, TADF materials and fluorescent chromophores are co-doped in host matrixes to act as sensitizers and emitters respectively. Under electrical excitation, triplet excitons formed on TADF sensitizers can be up-converted into singlet ones by RISC process, which are then transferred to singlet (S 1 ) states of fluorescent chromophores via Förster resonance energy transfer (FRET) for light emission.…”