Efficient management of excitons in near-infrared organic light-emitting diodes employing interlayer sensitization strategy

Abstract

Near-infrared (NIR) organic light-emitting diodes (OLEDs) have garnered significant attention owing to their promising applications in military, medical, and agricultural fields. However, the intrinsic characteristics of narrow energy gap and planar molecular structure of NIR organic materials result in low electroluminescence (EL) efficiency in OLEDs. Achieving both high efficiency and long-wavelength emission in NIR OLEDs remains a significant challenge. In this study, an interlayer sensitization strategy was employed to manage excitons and achieve highly efficient NIR-OLEDs with an emission peak wavelength exceeding 700 nm. Significantly, DMAC-DPS:TTPA was utilized as the sensitizing layer (SEL), while PPF:APDC-DTPA served as the emitting layer (EML). The separation of the EML and the SEL could effectively suppress direct carrier recombination in APDC-DTPA molecules, ensuring that the NIR emission primarily originates from exciton energy transfer from the sensitizer. Additionally, a spacer layer was incorporated to modulate exciton concentration within the NIR emitter and mitigate exciton quenching. By optimizing the doping concentration of TTPA sensitizer, highly efficient NIR OLEDs were achieved. The maximum external quantum efficiency (EQE) reached 6.61 %, with a NIR emission peak at 720 nm. These results provide a promising route to develop high efficiency NIR OLEDs for practical applications.