Excited states engineering enables efficient near-infrared lasing in nanographenes
Excited states engineering enables efficient near-infrared lasing in nanographenes
复制标题
DOI：
10.1039/d1mh00846c
复制
发表时间：
2021-09-24
影响因子：
13.3
通讯作者：
Lanzani, Guglielmo
中科院分区：
文献类型：
--
作者：
Paterno, Giuseppe M.;Chen, Qiang;Lanzani, Guglielmo
受激发射（SE）和暗态（即电荷和三重态）吸收之间的光谱重叠，特别是在近红外（NIR）中，代表了有机半导体中最有效的增益损失通道之一。最近，自下而上合成原子级精确的石墨烯纳米结构或纳米石墨烯（NG），为开发具有光学增益特性的环境和化学稳定的材料开辟了一条新途径。然而，同样在这种情况下，增益和吸收损耗之间的相互作用阻碍了在NIR中实现有效的激光作用。在这里，我们证明了两个荧蒽酰亚胺基团引入到NG核心导致比前体NG分子更多的红移发射（685与615 nm），并且还具有更大的斯托克斯位移（45 nm与2 nm，1026 cm（-1）与53 cm（-1），分别）。光物理的结果表明，除了最小化的基态吸收损失，这种取代允许抑制有害的激发态吸收在近红外光谱，这可能是由一个黑暗的状态与电荷转移字符和三重态。这使得近红外激光（720 nm）从所有的解决方案处理的分布式反馈设备与一个数量级的阈值比以前报道的近红外发射NG低。这项研究代表了NG领域的一个进步，一般来说，有机半导体光子学，朝着廉价和稳定的近红外激光器的发展。
The spectral overlap between stimulated emission (SE) and absorption from dark states (i.e. charges and triplets) especially in the near-infrared (NIR), represents one of the most effective gain loss channels in organic semiconductors. Recently, bottom-up synthesis of atomically precise graphene nanostructures, or nanographenes (NGs), has opened a new route for the development of environmentally and chemically stable materials with optical gain properties. However, also in this case, the interplay between gain and absorption losses has hindered the attainment of efficient lasing action in the NIR. Here, we demonstrate that the introduction of two fluoranthene imide groups to the NG core leads to a more red-shifted emission than the precursor NG molecule (685 vs. 615 nm) and also with a larger Stokes shift (45 nm vs. 2 nm, 1026 cm(-1)vs. 53 cm(-1), respectively). Photophysical results indicate that, besides the minimisation of ground state absorption losses, such substitution permits to suppress the detrimental excited state absorption in the NIR, which likely arises from a dark state with charge-transfer character and triplets. This has enabled NIR lasing (720 nm) from all-solution processed distributed feedback devices with one order of magnitude lower thresholds than those of previously reported NIR-emitting NGs. This study represents an advance in the field of NGs and, in general, organic semiconductor photonics, towards the development of cheap and stable NIR lasers.