Fused nonacyclic carbonyl/nitrogen-containing multi-resonance emitters with simultaneously redshifted and narrowed emission spectra for high-efficiency solution-processed OLEDs

Abstract

Multiple resonance (MR) emitters are attractive candidates for ultra-high-definition displays due to their narrowband emissions and high luminescent efficiency. However, it has been challenging to develop MR emitters with elongated emission wavelengths because they often encounter broadened emissive spectra. Here we report two nonacyclic carbonyl/nitrogen (CO/N)-containing MR emitters (NCON-TB and NCON-Mes) by fusing two pentacyclic indolo[3,2,1-de]acridinone skeletons through phenyl segment bridging the carbonyl and nitrogen atom. Compared to parent pentacyclic counterpart, the fused nonacyclic emitters not only exhibit largely red-shifted emissions (by ∼90 nm) owing to enhanced short-range charge transfer, but also reveal much narrowed emission spectra by reducing stretching vibrations of molecular skeleton and CO bonds, giving pure green emissions peaked at 520 ∼ 521 nm with full width at half-maximum of 28 nm/0.13 eV and high photoluminescence quantum yield up to 94 %. Solution-processed organic light-emitting diodes (OLEDs) employing NCON-Mes bearing four peripheral mesitylene substituents as emitter exhibit narrowband electroluminescence at 524 nm with maximum external quantum efficiency of 27.7 %, representing the best device efficiency for solution-processed OLEDs based on CO/N-containing MR emitters so far.