Enabling Record-high Deep-Red/Near-Infrared Electroluminescence Through Subtly Managing Intermolecular Interactions of a Thermally Activated Delayed Fluorescence Emitter

Deep-red/near-infrared (DR/NIR) organic light-emitting diodes (OLEDs) are promising for applications such as night-vision readable marking, bioimaging, and photodynamic therapy. To tune emission spectra into the DR/NIR region, red emitters generally require assistance from intermolecular interactions. But such interactions generally lead to sharp efficiency declines resulting from unwanted quenching events. To overcome this challenge, herein, an advanced method via strategically managing the intermolecular interactions of thermally activated delayed fluorescence (TADF) emitters is proposed. The proof-of-concept molecule called DCN-SPTPA exhibits impressive resistance to quenching while delivering controllable aggregation behavior for redshifting the emission by installing an end-spiro group. Consequently, two emitters demonstrate similar photophysical properties and device performance at very low doping levels; while DCN-SPTPA-based OLEDs demonstrate a 1.3-1.4-fold enhancement of the external quantum efficiencies (EQEs) with respect to the control molecule at 5-20 wt.% doping ratios, affording DR/NIR emission at 656, 688, 696, and 716 nm with record-breaking EQEs of 36.1%, 29.3%, 28.2%, and 24.0%, respectively. Moreover, DCN-SPTPA-based nondoped NIR device also retains a state-of-the-art EQE of 2.61% peaked at 800 nm. This work first demonstrates instructive guidance for accurately manipulating the intermolecular interactions of red TADF emitters, which will spur future developments in high-performance DR/NIR OLEDs.