Ultrastable and Low‐Threshold Random Lasing from Narrow‐Bandwidth‐Emission Triangular Carbon Quantum Dots

Abstract

colloidal semiconductor quantum dots (QDs) especially the Cd 2+ -based QDs such as CdSe and CdTe emerged as good candidates for the development of random lasers since their unique and attractive optical characteristics, such as high quantum yield (QY), small Stokes shifts, and narrow emission bandwidths, can facilitate the ultrafast build-up of population inversion and the subsequent optical amplification at a low pump energy density. [4][5][6] Considerable efforts have been invested and remarkable progress has been made on the design and fabrication of highly efficient random lasers with high spectral purities based on the perovskites and Cd 2+ -based QDs in simple device configurations. [7][8][9][10] However, the intrinsic instability as well as the severe toxicity are still significant impediments to deploying perovskites and Cd 2+ -based QDs as next-generation light-emitting materials for future ultrastable and low-threshold random lasing applications. [7][8][9][10] The bandgap emission carbon quantum dots (BE-CQDs) have recently emerged as a promising alternative to perovskites and traditional semiconductor QDs for optoelectronic devices, such as solution-processed electroluminescent light-emitting diodes (LEDs) [11][12][13] and lasers, by taking advantage of carbon's intrinsic merits of high stability, low cost, high abundance, and environment friendliness. [14][15][16][17][18][19][20][21] In our recent work, for the first time, we have realized full-color random lasing with lasing thresholds in the range of 2.1-5.8 mJ cm −2 in blue, green, red, and white colors based on bright multicolor fluorescent BE-CQDs. [14] The random lasers show much better operating stability than those of perovskites and Cd 2+ -based QDs, laying a solid foundation for developing the next-generation laser technology. [7][8][9][10][22][23][24] However, the large Stokes shifts (>80 nm) and the large full width at half maximum (FWHM > 80 nm) of the BE-CQDs inevitably result in the dissipation of exciton energy into heat and prevent sustaining population inversion during the pumping process, thus fundamentally limiting the further performance improvement especially on pump thresholds for the random lasing. [14][15][16][17][18][19][20][21] Without a doubt, the best approach to realizing tunable stable CQDs-based random lasers with a much lower pump threshold for lasing is to develop bright multicolor fluorescent CQDs with small Stokes shifts (<20 nm) and small FWHM (<40 nm).Most recently, we have demonstrated the first synthesis of highly efficient narrow bandwidth emission triangular CQDsThe development of ultrastable and low-threshold random lasers has long been the subject of intense academic research, in anticipation for widespread applications spanning from military weapon devices, biomedical therapy, and materials processing to energy savings. Reported here is the first example of ultrastable and low-threshold random lasing emissions ranging from blue to red based on narrow bandwidth emission triangular carbon quantum dots (CQDs)....

Overview of Computational Simulations in Quantum Dots

“…The maximal absorption peak of Cd 2 Te 2 QDs in the ultraviolet-visible absorption spectrum is at 584 nm. The peak location shifts to 534 nm in Cd 2 Te 2 -(SiO 2 ) 24 . The excited process is found to have a direct electronic transition from the occupied core states to the outer shell excited states.…”

“…At the nanometer length scale, armchair edges significantly contribute to the DOS and lead to a clean band gap of the graphene QDs model. It is also concluded that graphene QDs are not required to contain func- 24 . The insert is the plot of molecular orbitals corresponding to the excited state (HOMO-2!LUMO) with a wavelength of 534 nm.…”

“…Aside from the core-shell structures, various approaches have been proposed to modify the properties of QDs such as surface reconstruction, [21] deep-level doping [22] and bidisperse mixture. [23] Other popular QD structures include carbon dots [24][25][26] and two dimensional (2D) heterostructures. [27][28][29] Carbon dots are low cost and environment-friendly materials with several advantages such as excellent performances in photoluminescence, photostability and biocompatibility, which enable their implementations in solar energy harvesting and fluorescence imaging.…”

Application advances of carbon quantum dots in optoelectronic devices

“…目前, CQDs的发光波 长已经可以由深紫外区扩展到近红外区 [9] , 且蓝、绿、 红 光 C Q D s 的 Q Y 最 高 分 别 已 经 高 达 9 9 % ， 8 1 % 和 80% [10,11] . 由于其具有较高的电子迁移率、较长的热电 子寿命、宽的光学吸收, 使其在白光发光二极管(white light-emitting diode, WLED) [12~14] 、QDs电致发光二极 管(QD-based electroluminescent light-emitting diode, QLED) [15~17] 、激光二极管(laser diode, LD) [18,19] 、可见 光通信(visible light communication, VLC) [12,13] 、聚合物 太阳能电池(polymer solar cell, PSC)…”

Random laser in vitreous matrix with inhomogeneous scatterer distribution and a statistical approach in polymeric nanofiber random laser

“…With this in mind, a goal for random laser material architecture is their fabrication with extremely low cost and practically disposable. Other issues concerning random lasing had some alternatives already presented in the literature such as beam directionality 25 , low laser energy threshold [26][27][28] and ease of manufacturing 29 .…”