Near-Infrared Lasing from Small-Molecule Organic Hemispheres

TLDR

Near‑infrared lasers are essential for telecom, spectroscopy, displays, and biomedical imaging, yet inorganic III‑V devices are costly and complex, while organic semiconductors offer tunable properties but suffer from low stimulated emission and exciton‑exciton annihilation that limit NIR lasing. The authors designed and synthesized the amphiphilic molecule DPHP to self‑assemble into micrometer‑sized hemispheres that act as both a NIR emission medium and a high‑Q whispering‑gallery‑mode microcavity. The DPHP hemispheres exhibit a 15.2 % photoluminescence quantum efficiency and a high‑Q (~1.4 × 10³) whispering‑gallery‑mode cavity, enabling efficient NIR lasing. The hemispheres achieve a radiative rate of ~1.98 × 10⁹ s⁻¹, suppress exciton‑exciton annihilation, and reach NIR lasing with a low threshold of ~610 nJ cm⁻² at room temperature, marking a significant advance toward compact organic NIR light sources.

Abstract

Near-infrared (NIR) lasers are key components for applications, such as telecommunication, spectroscopy, display, and biomedical tissue imaging. Inorganic III-V semiconductor (GaAs) NIR lasers have achieved great successes but require expensive and sophisticated device fabrication techniques. Organic semiconductors exhibit chemically tunable optoelectronic properties together with self-assembling features that are well suitable for low-temperature solution processing. Major blocks in realizing NIR organic lasing include low stimulated emission of narrow-bandgap molecules due to fast nonradiative decay and exciton-exciton annihilation, which is considered as a main loss channel of population inversion for organic lasers under high carrier densities. Here we designed and synthesized the small organic molecule (E)-3-(4-(di-p-tolylamino)phenyl)-1-(1-hydroxynaphthalen-2-yl)prop-2-en-1-one (DPHP) with amphiphilic nature, which elaborately self-assembles into micrometer-sized hemispheres that simultaneously serves as the NIR emission medium with a photoluminescence quantum efficiency of ∼15.2%, and the high-Q (∼1.4 × 10(3)) whispering gallery mode microcavity. Moreover, the radiative rate of DPHP hemispheres is enhanced up to ∼1.98 × 10(9) s(-1) on account of the exciton-vibrational coupling in the solid state with the J-type molecular-coupling component, and meanwhile the exciton-exciton annihilation process is eliminated. As a result, NIR lasing with a low threshold of ∼610 nJ/cm(2) is achieved in the single DPHP hemisphere at room temperature. Our demonstration is a major step toward incorporating the organic coherent light sources into the compact optoelectronic devices at NIR wavelengths.