Highly Efficient Near‐Infrared Organic Light‐Emitting Diode Based on a Butterfly‐Shaped Donor–Acceptor Chromophore with Strong Solid‐State Fluorescence and a Large Proportion of Radiative Excitons

The development of near-infrared (NIR) organic light-emitting diodes (OLEDs) is of growing interest. Donor-acceptor (D-A) chromophores have served as an important class of NIR materials for NIR OLED applications. However, the external quantum efficiencies (EQEs) of NIR OLEDs based on conventional D-A chromophores are typically below 1 %. Reported herein is a butterfly-shaped D-A compound, PTZ-BZP. A PTZ-BZP film displayed strong NIR fluorescence with an emission peak at 700 nm, and the corresponding quantum efficiency reached 16 %. Remarkably, the EQE of the NIR OLED based on PTZ-BZP was 1.54 %, and a low efficiency roll-off was observed, as well as a high radiative exciton ratio of 48 %, which breaks through the limit of 25 % in conventional fluorescent OLEDs. Experimental and theoretical investigations were carried out to understand the excited-state properties of PTZ-BZP.