Short-Wavelength Infrared Organic Light-Emitting Diodes from A-D-A'-D-A Type Small Molecules with Emission beyond 1100nm.

Abstract

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, the study reports 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 and 1.13eV, respectively. SWIR electroluminescence (EL) emission from OLEDs based on NTQ and BTQ is achieved, with emission peaks at 1140 and 1175nm, 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 5200mA cm-2 , the resultant SWIR OLEDs based on NTQ exhibit a maximal radiant exitance of =1.12mW cm-2 . Furthermore, the NTQ-based OLEDs also possess sub-gap turn-on voltage of 0.85V, which is close to the physical limits derived from the generalized Kirchhoff and Planck equation. This work demonstrates that A-D-A'-D-A type small molecules offer significant promise for NIR/SWIR emitting material innovations.