Thermally activated delayed fluorescence exciplexes with phosphor components realizing deep-red to near-infrared electroluminescence

Abstract

Compared with single-molecule thermally activated delayed fluorescence emitters, exciplexes can simplify the complicated molecule design and synthesis and have the superiority of conveniently realizing spectra with a bathochromic shift via mixing donor and acceptor components. In this work, we develop a series of novel exciplexes with phosphor components showing emission in the range of deep-red to near-infrared (NIR). The phosphor-incorporated exciplexes would improve the utilization of triplet excitons due to the spin–orbit coupling (SOC) effect of heavy metal atoms in phosphors. By employing B2PyMPM, B3PyMPM and B4PyMPM as acceptors, three exciplexes were first constructed with phosphor Ir-817. Optimized B2PyMPM:Ir-817, B3PyMPM:Ir-817 and B4PyMPM:Ir-817-based OLEDs show electroluminescence (EL) peaks at 612, 640 and 672 nm and maximum external quantum efficiencies (EQE) of 3.1%, 1.45% and 1.03%, respectively. To further develop exciplexes with NIR emission, TRZ-1SO₂, TRZ-2SO₂ and TRZ-3SO₂ with stronger electron-withdrawing abilities were chosen as the acceptors. Notably, the TRZ-3SO₂:Ir-817-based device exhibits an EL peak at 746 nm and a maximum EQE of 0.20%. These results demonstrate the potential and feasibility of using phosphor-incorporated exciplexes in the development of NIR exciplexes.