Two efficient blue thermally activated delayed fluorescence compounds, B-oCz and B-oTC, composed of ortho-donor (D)-acceptor (A) arrangement were designed and synthesized. The significant intramolecular D-A interactions induce a combined charge transfer pathway and thus achieve small ΔE and high efficiencies. The concentration quenching can be effectively inhibited in films of these compounds. The blue non-doped organic light emitting diodes (OLEDs) based on B-oTC prepared from solution processes shows record-high external quantum efficiency (EQE) of 19.1 %.
In this communication, we report a new greenish-blue-emitting Cu(i) complex, Cu4Cl4(NP)2, a with high photoluminescence quantum yield of 90% and a short decay time of 9.9 μs. Due to the strong SOC combined with the small activation energy ΔEST, the emission at room temperature consists of approximately equivalent fast phosphorescence and TADF.
Herein, we present a new strategy in which highly emissive
thermally
activated delayed fluorescence (TADF) materials can be obtained from
modifying or tuning a non-TADF donor (D)–acceptor (A)-type
organic molecule via coordination of the metal ionic fragment. Theoretical
calculation and photophysical properties reveal that the D–A-type
free ligand emits both weak fluorescence and dual room-temperature
phosphorescence, whereas the two Ag(I) complexes display efficient
blue TADF, exhibiting photoluminescence quantum yields nearly 100%
in films with short decay lifetimes (τ ≈ 6 μs).
This is attributed to the four optimized parameters induced by Ag(I)
coordination: (1) narrow singlet (S1)–triplet (T1) energy gaps (ΔE
ST). (2)
T1 states have a hybrid local excitation and charge transfer
(CT) character, and S1 states have a predominant CT character.
Both the parameters facilitate reverse intersystem crossing. (3) Radiative
rate constant (k
r(S1→S0)) is increased.
(4) Molecular rigidity is strengthened. For the first time, this work
shows a powerful method to design efficient ligand-centered TADF in
Ag(I) complexes based on the conventional D–A-type molecule,
which significantly enriches the chemical space for the development
of TADF materials.
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