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We presented in this paper a photoassisted ligand exchange approach whereby light will be introduced to facilitate the replacement of oleic acid (OA) ligand molecules over PbSe quantum dots (QDs). The ligand-exchanged QDs were used to fabricate quantum dot light-emitting-diodes (QD-LEDs), which outperform the devices comprising the QDs without liga...
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We fabricated and packaged a blue micro-LED with a diameter of 50-µm based on a single layer of InGaN quantum dot (QD) micro-LED for VLC, and then revealed its impedance characteristics by fitting with a modified equivalent circuit model.
Citations
... When fabricating PbSe colloidal quantum dots (CQDs), we always use ligands with long alkyl chains [16]. Although the presence of long-chain ligands protects the CQDs from oxidation and allows them to disperse well in solution after synthesis, it inhibits CQD-to-CQD carrier transport. ...
By the photodetector manufactured using traditional semiconductor materials, such as HgCdTe and InGaAs, it is difficult to broaden the application range of such photodetectors due to their high cost and complex manufacturing process. PbSe colloidal quantum dots (CQDs) have the potential to shift the working range of photodetector from visible to infrared wavelength region, and it also has high photoresponsivity. Herein, we report the characterization of PbSe CQDs synthesized using a facile solution process, as well as the relationship between the size of nanocrystal and the reaction temperature. The films of PbSe CQDs are deposited using the layer-by-layer (LbL) spin-coating method, which is then used to fabricate the photoconductive device. The fabricated device is found to have an efficient response in a broad spectrum range of 400-2600 nm. The device maintains good responsivity of ~320 mA/W at room temperature. Its external quantum efficiency was quite high in the shorter wavelength infrared region, and it has approximately 14% external quantum efficiency (EQE) at 2520 nm. The device demonstrated excellent performance, confirming that PbSe colloidal quantum dots is a promising material for future broadband spectrum photodetectors.
... In 1874 Ferdinand Braun was the first to report electrical rectification with natural galena (lead sulfide, PbS) [1]. From then on, lead chalcogenides (PbS, PbTe and PbSe) and their alloys (PbSeTe, PbSnSe, PbSnTe and PbSnSeTe) were widely used as semiconductor devices, such as light emitting diodes [2], laser diodes [3], infrared photodetectors [4], solar cells [5] and thermoelectric devices [6], due to their excellent photoelectric and thermoelectric properties. ...
Indium-doped PbSe thin films deposited on Si(111) by magnetron sputtering were annealed at different temperatures and characterized using the X-ray diffraction, Fourier transform infrared spectroscopy and physical properties measurement system. After the annealing treatment, an oxidation layer containing PbSe, PbO, SeO2 and In2Se3 is formed on the film surface. The optical band gap of the annealed samples increases to a maximum of 0.276 eV at 150 °C, and then decreases with the annealing temperature due to the position shift of the valence band maximum and the conduction band minimum. The photoelectric sensitivity of the annealed indium-doped PbSe thin films increases by 1.5–2 times, compared with the untreated samples. Moreover, the average value of the resistance change rate increases almost linearly with the annealing temperature due to the concentration of the dark charge carriers increases with the annealing temperature confirmed by the Hall effect measurements.
... In 1874 Ferdinand Braun was the first to report electrical rectification with natural galena (lead sulfide, PbS) [1]. From then on, lead chalcogenides (PbS, PbTe and PbSe) and their alloys (PbSeTe, PbSnSe, PbSnTe and PbSnSeTe) were widely used as semiconductor devices, such as light emitting diodes [2], laser diodes [3], infrared photodetectors [4], solar cells [5] and thermoelectric devices [6], due to their excellent photoelectric and thermoelectric properties. ...
... QDs are colloidal nanocrystalline semiconductors with special luminescent properties with relatively spherical morphology, narrow emission bands (typically 20-30 nm full-width at half-maximum intensity) and high photochemical stability. [1] Luminescent QDs have great applications in light-emitting diodes, [2] biological imaging, [3] and sensors. [4] Tin oxide (SnO 2 ) is a great semiconductor material with an exciton Bohr radius of approximately 2.7 nm. [5] In particular, SnO 2 has been widely used as gas sensors for monitoring the environment and as catalysts. ...
An ecofriendly synthesis is established to obtain ultra-small SnO2 nanoparticles (NPs) doped with metals by a hydrothermal method using only tin tetrachloride, urea, and water as reagents. This synthesis was done in a short period time at low temperature and without surfactants. Microscopy analysis revealed the formation of doped tin oxide NPs with a diameter smaller than 2.8 nm. Un-doped and doped tin oxides were obtained with a tetragonal type rutile structure with an average surface area of 348 m2/g.
... Moreover, PbSe has the largest Bohr's radius of about 47 nm and relatively small effective mass of the exited electronhole pair, compared with other lead chalcogenide materials, which allows remarkable quantum confinement and tunable band gap in large crystals [3]. For these reasons, PbSe has been widely used in infrared detectors [4], light emitting devices [5], laser diodes [6], solar cells [7], thermoelectric devices [8] and so on. ...
... Hu et al. [209] reported on a photoassisted ligand exchange approach whereby light was introduced to facilitate the replacement of oleic acid (OA) ligand molecules around PbSe quantum dots (QDs). The ligand-exchanged QDs were used to fabricate quantum dot light-emitting diodes (QD-LEDs), which outperform devices fabricated with QDs without ligand replacement. ...
To improve the usability and operability of the hybrid-identification reconnaissance radar for individual use, a voice identification System was designed. By using SPCE061A audio signal microprocessor as the core, a digital signal processing technology was used to obtain Doppler radar signals of audio segments by audio cable. Afterwards, the A/D acquisition was conducted to acquire digital signals, and then the data obtained were preprocessed and adaptively filtered to eliminate background noises. Moreover, segmented FFT transforming was used to identify the types of the signals. The overall design of radar voice recognition for an individual soldier was thereby fulfilled. The actual measurements showed that the design of the circuit improved radar resolution and the accuracy of the radar identification.
