Organic semiconductors possessing tightly bound Frenkel excitons are known to be attractive candidates for demonstrating polariton lasing at room temperature. As polariton lasing can occur without inversion, it is a potential route to very low threshold coherent light sources. However, so far, the thresholds of organic polariton lasers have generally been much higher than those of organic photon lasers. Here this problem has been addressed by investigating two new organic molecules with a structure combining fluorene and carbazole groups. The materials are readily deposited from solution and exhibit high photoluminescence quantum yields, high absorption coefficients, and large radiative decay rates in neat films. Room temperature polariton lasing is realized in both materials with incident thresholds of 13.5 and 9.7 µJ cm⁻², corresponding to absorbed thresholds of 3.3 and 2.2 µJ cm⁻², respectively. These are the lowest values reported to date for polariton lasing in organic semiconductor materials, and approach typical values for organic photon lasers. The step-like power dependent blue-shift of polariton modes indicates an interplay between different depletion channels of the exciton reservoir. This work brings practical room temperature polaritonic devices and future realization of electrically driven polariton lasers a step closer.

中文翻译：

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来自芴基低聚物的低阈值室温偏振子激光

众所周知，拥有紧密结合的弗伦克尔激子的有机半导体是在室温下展示极化子激光的有吸引力的候选者。由于偏振子激光可以在没有反转的情况下发生，因此它是通向极低阈值相干光源的潜在途径。然而，到目前为止，有机偏振子激光器的阈值普遍远高于有机光子激光器的阈值。在这里，这个问题已通过研究具有结合芴和咔唑基团的结构的两种新有机分子得到解决。这些材料很容易从溶液中沉积，并在纯薄膜中表现出高光致发光量子产率、高吸收系数和大辐射衰减率。两种材料都实现了室温极化激射，入射阈值为 13.5 和 9.7 µJ cm^-2，分别对应于 3.3 和 2.2 µJ cm ^{-2 的}吸收阈值。这些是迄今为止有机半导体材料中极化子激光所报道的最低值，接近有机光子激光器的典型值。极化子模式的阶梯状功率相关蓝移表明激子库的不同耗尽通道之间存在相互作用。这项工作使实用的室温极化装置和电驱动极化激光器的未来实现更近了一步。