Short-wavelength Infrared Organic Light-emitting Diodes from A-D-A'-D-A type Small Molecules with Emission Beyond 1100 nm.

Short-wavelength infrared (SWIR) organic light-emitting diodes (OLEDs) have attracted great interest due to their potential applications in biological imaging, infrared lighting, optical communication, environmental monitoring and surveillance. Due to an intrinsic limitation posed by the energy-gap law, achieving high-brightness in SWIR OLEDs remains a challenge. Herein, we report the use of novel A-D-A'-D-A type small molecules NTQ and BTQ for high-performance SWIR OLEDs. Benefiting from multiple D-A effect in conjugated skeleton, the small molecules NTQ and BTQ exhibit narrow optical gaps of 1.23 eV and 1.13 eV, respectively. We achieved SWIR electroluminescence (EL) emission from OLEDs based on NTQ and BTQ, with emission peaks at 1140 nm and 1175 nm, respectively. Not only owing to a negligible efficiency roll-off across the full range of applied current density but also the ability to afford a high operation current density of 5200 mA cm -2 , the resultant SWIR OLEDs based on NTQ exhibit a maximal radiant exitance of ∼1.12 mW cm -2 . Furthermore, the NTQ-based OLEDs also possess sub-gap turn-on voltage of 0.85 V, which is close to the physical limits derived from the generalized Kirchhoff and Planck equation. Our work demonstrates that A-D-A'-D-A type small molecules offer significant promise for NIR/SWIR emitting material innovations. This article is protected by copyright. All rights reserved.