Localized Excitonic Electroluminescence from Carbon Nanodots

Abstract

Localized excitons are expected to achieve high-performance electroluminescence and have been widely investigated in GaN-based light-emitting diodes (LEDs). Although carbon nanodot (CD) based LEDs have been achieved with the radiative recombination of electrons and holes, localized excitonic electroluminescence has been not reported before. In this Letter, localized excitonic electroluminescent devices have been fabricated using fluorescent CDs as an active layer. The CDs show strong localized excitonic yellow emission with a fluorescence quantum yield of 76% and Stokes shift of 2.1 eV. The CD-based LEDs present a sub-bandgap turn-on voltage of 2.4 V and a maximum luminance of 60.2 cd m–2, which is the lowest driving voltage among the CD-based electroluminescent devices. Localized centers trap carriers effectively, resulting in sub-bandgap light emission. The current results manifest that localized excitons may furnish a promising approach to boost the development of CD-based LEDs.

Facilely synthesized carbon dots and configurated light-emitting diodes with efficient electroluminescence

“…Our results differ from those previously reported in the literature, in which the exciton absorption bands of CDs appear only within the ultraviolet region. 7,11,12,33 Here, we distinctly observe absorption in the visible range at 485 and 520 nm. In-depth investigations indicate that the 280–380 nm range is attributed to n–π* transitions, mainly including the oxygen functional groups of C–O and CO. 34 Peaks in the visible region at 380–800 nm are usually associated with the excitonic absorption band, indicating the high conjugation and high quality of the CDs.…”

“…2a) of the CDs show a broad diffraction peak centered at around 2 θ = 21.5°, which is slightly shifted to a lower diffraction angle compared with the standard peak position (2 θ = 23°) of the (002) carbon crystal plane. 11 This may be due to the synergistic effect between graphitic carbons and amorphous carbons.…”

“…Newly emerged carbon dots (CDs) not only overcome this intractable problem but also possess the advantages of low cost, sustainable development, and abundant carbon resources. [10][11][12][13][14][15][16][17] In recent years, extensive investigations have demonstrated that CDs are good candidates for electron donors, acceptors, and fluorescence (with a quantum yield of up to 60-80%). [18][19][20][21][22][23] This undoubtedly boosts CDs as promising emitters for LEDs and promotes diversified competition in stylish displays and solid-state lighting.…”

“…9 After a decade of research, the latest reported CD-based LEDs attain a maximum luminous efficiency of 0.036 cd A −1 , luminance of 60.2 cd m −2 , and power efficiency of 0.025 lm W −1 . 11 In addition, solution-processed technology is highly favored in optoelectronic devices because of its large area, low cost, and scalable manufacturing. 31 High-quality CDs are urgently required for advancing CD-based LEDs.…”

Nanowire-Shaped MoS2@MoO3 Nanocomposites as a Hole Injection Layer for Quantum Dot Light-Emitting Diodes

“…Among such strategies, employing transition-metal dichalcogenides has attracted the attention of the research community. The most promising one is molybdenum-based structures that already demonstrated that they are more active than other materials to promote the charge transport in optoelectronic devices. , Using MoO 3 or MoS 2 nanostructures as a separate layer or additive in the PEDOT/PSS layer has been reported in various LEDs with different light-emitting layers such as perovskite NCs, Cd-based QDs, carbon dots, InP-based QDs, and even organic molecules . Nonetheless, in most cases, minimal attention has been dedicated to the synthesis of such MoO 3 or MoS 2 nanoparticles.…”