What question did this study set out to answer?

The study aims to improve reverse intersystem crossing rates and suppress concentration quenching in narrowband OLEDs.

January 24, 2026Advanced Functional Materials0 citations

Narrowband Emitters with Fast Reverse Intersystem Crossing and Suppressed Concentration‐Quenching Enabled by Engineering the Donor in a Through‐Space Charge‐Transfer System with A Multiple Resonance Acceptor

ZWZetian WangCentral China Normal University YSYongjun SongHubei University of Arts and Science DZDajun ZhuangCentral China Normal University

Key Points

The study aims to improve reverse intersystem crossing rates and suppress concentration quenching in narrowband OLEDs.
Developed new donor materials including IPXZ, IPTZ, and IPSeZ for a typical MR acceptor
Utilized a through-space charge transfer system to enhance the performance of emitters
Measured k RISC rates and photoluminescence efficiencies in different doping concentrations
Achieved k RISC values up to 5.0 × 10 5 s −1, significantly higher than 1.0 × 10 4 s −1 for the standard acceptor
Narrowband blue-green emission maintained in 5-20 wt.% doped films with high photoluminescence efficiencies
Maximum external quantum efficiencies reached 35.2% and remained above 27.1% at 20 wt.% doping concentration.

Abstract

ABSTRACT Multiple resonance (MR) emitters demonstrate great potential for fabricating narrowband organic light‐emitting diodes (OLEDs), which, however, show low reverse intersystem crossing (RISC) rates ( k RISC ) and severe concentration‐quenching. Here, indolo3,2,1‐ kl phenoxazine (IPXZ), indolo3,2,1‐ kl phenothiazine (IPTZ), and indolo3,2,1‐ kl phenoselenazine (IPSeZ) are developed as donors for a typical MR acceptor (DtBuCzB) in a through‐space charge transfer system, affording MR‐TADF materials ( BN1 , BN2, and BN3 , respectively) with high k RISC and largely suppressed concentration‐quenching. Close, cofacial donor/DtBuCzB alignments are formed within the emitters, which effectively accelerates the RISC and protects DtBuCzB from aggregation, especially for BN2 / BN3 with S / Se ‐containing donors. In the 2 wt.% doped films, the emitters exhibit narrowband blue‐green emission with high k RISC values up to 5.0 × 10 5 s −1 , which are markedly enhanced compared to that of DtBuCzB (1.0 × 10 4 s −1 ). In the 5–20 wt.% doped films, the emitters maintain narrowband emission and show high photoluminescence efficiencies, and the intermolecular donor/DtBuCzB interactions further enhance the k RISC values (up to 10 6 s −1 ). Non‐sensitized narrowband OLEDs using the emitters show maximum external quantum efficiencies (EQEs) up to 35.2% and EQEs at 1000 cd m −2 up to 26.1%. The maximum EQEs remain up to 27.1% at the 20 wt.% doping concentration.

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