Near‐Infrared Lasing in Four‐Zigzag Edged Nanographenes by 1D versus 2D Electronic π‐Conjugation

Abstract

The search of compounds emitting in the near-infrared (NIR) has been accelerated owing to their use in biomedical and telecommunications applications. In this regard, nanographenes (NGs) are attractive materials adequate for integration with other technologies, which have recently demonstrated amplified spontaneous emission (ASE) and lasing across the visible spectrum. Here, the optical and ASE properties of four-zigzag edged NGs of the [m,n]peri-acenoacene family are reported, whose size is increased through conjugation extension by varying n (from 3 to 5) while keeping m = 2. Results show that such 1D conjugation extension method is more efficient in terms of shifting the photoluminescence (PL) to the infrared (PL at 710 nm in the larger compound, PP-Ar) than through 2D conjugation extension as in previously reported NGs (PL at 676 nm with the largest compound FZ3, with n = 3 and m = 4). Additionally, PP-Ar shows dual-ASE (at 726 and 787 nm), whose origin is elucidated through Raman and transient absorption spectroscopies. These compounds' potential for red and NIR lasing is demonstrated through the fabrication of distributed feedback lasers with top-layer resonators. This study paves the way towards the development of stable low-cost all-plastic NIR lasers.

Small Size, Big Impact: Recent Progress in Bottom‐Up Synthesized Nanographenes for Optoelectronic and Energy Applications

“…Notably, [2,5] peri-acenoacene exhibits dual-ASE at 726 and 787 nm, respectively, promising for low-cost nearinfrared lasing applications. [88] Besides conventional optoelectronic applications, GQDs can also be considered single-photon emitters thanks to their excellent photochemical stability and low cost, holding great promise for next-generation quantum technologies such as quantum cryptography and communication. [30,82,92] To this end, further progress is required to explore GQDs with suppressed blinking and high brightness to realize the controllable quantum correlations.…”

Cove‐Edged Hexa‐peri‐hexabenzo‐bis‐peri‐octacene: Molecular Conformations and Amplified Spontaneous Emission

“…The narrowing of the emission linewidth appeared at a pump fluence of 2.4 mJ cm −2 (Figure 6c) with homogeneous ASE action in different regions of the film with a similar threshold (Figure 6d). Although HBPO exhibits a higher ASE threshold compared with reported zigzag‐edged NGs, [23–25] this is the first observation of ASE behavior in a contorted NG with cove‐edges, therefore enriching the future molecular design options.…”

“…The presence of ASE in a material is a prerequisite for lasing. In recent years, ASE was reported in a few zigzag-edged NGs with high fluorescence quantum yields [23][24][25] whereby bulky substituents are necessary to prevent the π-π stacking. [42] However, ASE has not yet been investigated in NGs with other edge structures.…”

“…Remarkably enough, two different contorted conformations of HBPO , “waggling” and “butterfly”, were confirmed by X‐ray crystallography, and the selectivity of conformations in the crystalline form can be manipulated by the choice of the solvents. Ultrafast transient absorption (TA) and amplified spontaneous emission (ASE) spectroscopies of HBPO revealed the potential of cove‐edged NGs as optical gain media for laser cavities, enriching the choices of edge structures besides the previously known zigzag periphery [23–25] …”

N,N′-Bis(3-methylphenyl)-N,N′-dyphenylbenzidine Based Distributed Feedback Lasers with Holographically Fabricated Polymeric Resonators

“…A limitation of these all-solution processed lasers is that their performance is generally inferior to that of lasers based on high-quality gratings engraved on inorganic substrates. At this respect, DFB lasers based on dichromated gelatin (DCG) polymeric resonators have demonstrated great success with a wide variety of dyes emitting in different regions of the optical spectrum (visible, blue and deep blue, and near-infrared), particularly when the resonator is located above the active film (top-layer resonator architecture, denoted as RT, accounting for "resonator on top", Figure 1a) [12][13][14][15][16]. This architecture is promising for the development of electrically pumped organic lasers because the grating spatially modulates the light emitted by the active material without the need of varying either the index or the thickness of the film, which remain constant.…”