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Record High External Quantum Efficiency of 19.2% Achieved in Light‐Emitting Diodes of Colloidal Quantum Wells Enabled by Hot‐Injection Shell Growth
摘要： Colloidal quantum wells (CQWs) are regarded as a highly promising class of optoelectronic materials, thanks to their unique excitonic characteristics of high extinction coefficients and ultranarrow emission bandwidths. Although the exploration of CQWs in light-emitting diodes (LEDs) is impressive, the performance of CQW-LEDs lags far behind other types of soft-material LEDs (e.g., organic LEDs, colloidal-quantum-dot LEDs, and perovskite LEDs). Herein, high-efficiency CQW-LEDs reaching close to the theoretical limit are reported. A key factor for this high performance is the exploitation of hot-injection shell (HIS) growth of CQWs, which enables a near-unity photoluminescence quantum yield (PLQY), reduces nonradiative channels, ensures smooth films, and enhances the stability. Remarkably, the PLQY remains 95% in solution and 87% in film despite rigorous cleaning. Through systematically understanding their shape-, composition-, and device-engineering, the CQW-LEDs using CdSe/Cd0.25Zn0.75S core/HIS CQWs exhibit a maximum external quantum efficiency of 19.2%. Additionally, a high luminance of 23 490 cd m?2, extremely saturated red color with the Commission Internationale de L’Eclairage (CIE) coordinates of (0.715, 0.283), and stable emission are obtained. The findings indicate that HIS-grown CQWs enable high-performance solution-processed LEDs, which may pave the path for future CQW-based display and lighting technologies.
关键词： core/shell structures,colloidal quantum wells,nanoplatelets,hot injection,light-emitting diodes
更新于2025-09-12 10:27:22
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Terahertz intersubband absorption of GaN/AlGaN step quantum wells grown by MOVPE on Si(111) and Si(110) substrates
摘要： We demonstrate terahertz intersubband absorptions in nitride step quantum wells (SQWs) grown by metal organic vapor phase epitaxy simultaneously on two different substrate orientations [Si(111) and Si(110)]. The structure of the SQWs consists of a 3 nm thick Al0.1Ga0.9N barrier, a 3 nm thick GaN well, and an Al0.05Ga0.95N step barrier with various thicknesses. This structure design has been optimized to approach a ?atband potential in the wells to allow for an intersubband absorption in the terahertz frequency range and to maximize the optical dipole moment. Structural characterizations prove the high quality of the samples. Intersubband absorptions at frequencies of 5.6 THz (k (cid:2) 54 lm), 7 THz (43 lm), and 8.9 THz (34 lm) are observed at 77 K on both substrate orientations. The observed absorption frequencies are in excellent agreement with calculations accounting for the depolarization shift induced by the electron concentration in the wells.
关键词： Si(111),GaN/AlGaN,step quantum wells,intersubband absorption,Si(110),MOVPE,terahertz
更新于2025-09-12 10:27:22
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Effect of Indium Composition on the Microstructural Properties and Performance of InGaN/GaN MQWs Solar Cells
摘要： In the present work, InGaN/GaN multiple quantum wells (MQWs) solar cells with different concentrations of indium have been investigated in-depth. It was demonstrated that applying a medium-high indium content (about 28%) does not facilitate solar cell photoelectric conversion efficiency due to the increase of edge dislocations. Moreover, the effects of different indium contents on InGaN/GaN MQWs solar cells were investigated and was revealed, that the short-circuit current density and photoelectric conversion efficiency are improved with the increase of indium contents. However, they show a noticeable reduction in the indium content of 28%. Furthermore, the optical properties and the behaviour of the microstructure defects were analysed. It was also demonstrated that the number of edge dislocations acted as non-radiation recombination centers increasing rapidly when the indium content reaches 28%, playing a key role in decreasing the active number of photon-generated carriers. As a result, the short-circuit current density and photoelectric conversion efficiency decrease obviously for an indium content of 28%. This work can provide insight into the origin of the degradation of these structures and the improvement of device design with medium-high indium contents.
关键词： solar cells.,InGaN/GaN multiple quantum wells (MQWs),microstructure and performance,Indium composition
更新于2025-09-12 10:27:22
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Electron-hole superfluidity controlled by a periodic potential
摘要： We propose controlling an electron-hole super?uid in semiconductor coupled quantum wells and double layers of a two-dimensional (2D) material by an external periodic ?eld. This can be created either by the gates periodically located and attached to the quantum wells or double layers of the 2D material or by the moiré pattern of two twisted layers. The dependence of the electron-hole pairing order parameter on the temperature, the charge carrier density, and the gate parameters is obtained by minimization of the mean-?eld free energy. The second-order phase transition between super?uid and electron-hole plasma, controlled by the external periodic gate ?eld, is analyzed for different parameters.
关键词： mean-?eld free energy,semiconductor coupled quantum wells,electron-hole super?uid,phase transition,external periodic ?eld,two-dimensional material
更新于2025-09-11 14:15:04
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[IEEE 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Ottawa, ON, Canada (2019.7.8-2019.7.12)] 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Atomistic analysis of transport properties of InGaN/GaN multi-quantum well
摘要： We present an atomistic analysis of transport properties of an InGaN/GaN multi-quantum well system. Our study is carried out in the combined frame of tight-binding and Non-Equilibrium Green’s Function theories. In our fully three-dimensional treatment, special attention is paid to the impact of random alloy ?uctuations on the electron transmission probability. The calculations reveal that the alloy microstructure signi?cantly impacts the transmission at least for the energetically lowest bound states in the quantum wells.
关键词： InGaN,atomistic description,quantum wells,transport properties
更新于2025-09-11 14:15:04
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Coulomb drag in strongly coupled quantum wells: Temperature dependence of the many-body correlations
摘要： We investigate the effect of the temperature dependence of many-body correlations on hole–hole Coulomb drag in strongly coupled GaAs/GaAlAs double quantum wells. For arbitrary temperatures, we obtained the correlations using the classical-map hypernetted-chain approach. We compare the temperature dependence of the resulting drag resistivities qDeTT at different densities with qDeTT calculated assuming correlations ?xed at zero temperature. Comparing the results with those when correlations are completely neglected, we con?rm that correlations signi?cantly increase the drag. We ?nd that the drag becomes sensitive to the temperature dependence of T (cid:2) 2TF, twice the Fermi temperature. Our results show excellent agreement with available experimental data.
关键词： Coulomb drag,many-body correlations,temperature dependence,quantum wells
更新于2025-09-11 14:15:04
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[IEEE 2018 Asia Communications and Photonics Conference (ACP) - Hangzhou (2018.10.26-2018.10.29)] 2018 Asia Communications and Photonics Conference (ACP) - Speed Characterization of InGaAs/GaAsSb Type-II Quantum Wells PIN Photodiodes
摘要： A normal incident InGaAs/GaAsSb type-II quantum wells PIN photodiode is demonstrated for 2μm wavelength high speed application. Results show this device has capability for 2μm high speed operation with 3dB-bandwidth of 2.93 GHz.
关键词： type-II quantum wells,high speed photodiode
更新于2025-09-11 14:15:04
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Multidimensional Coherent Spectroscopy of Semiconductors
摘要： Optical multidimensional coherent spectroscopy (MDCS) is a nonlinear spectroscopy technique where a material is excited by a series of laser pulses to produce a spectrum as a function of multiple frequencies. The technique’s ability to elucidate excited-state structure and interactions has made MDCS a valuable tool in the study of excitons in semiconductors. This review introduces the method and describes progress it has fostered establishing a better understanding of dephasing rates, coherent coupling mechanisms, and many-body interactions pertaining to optically generated electronic excitations in a variety of semiconductor material systems. Emphasis is placed on nanostructured gallium arsenide quantum wells and quantum dots, on quantum dots in other III–V and II–VI semiconductors, and on atomically thin transition metal dichalcogenides. Recent technical advances and potential future directions in the ?eld are also discussed.
关键词： quantum dots,excitons,quantum wells,Fourier-transform spectroscopy,transition metal dichalcogenides
更新于2025-09-10 09:29:36
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Al <i> <sub/>x</sub></i> Ga <sub/>1?</sub><i> <sub/>x</sub></i> N-Based Quantum Wells Fabricated on Macrosteps Effectively Suppressing Nonradiative Recombination
摘要： AlxGa1?xN-based quantum wells (QWs) are fabricated on AlN with macrosteps, which are formed by using vicinal sapphire and AlN (0001) substrates. The QWs on macrosteps (MS-QWs) show photoluminescence lifetimes of nearly 2 ns at an emission wavelength of 242 nm at room temperature (RT). This is the longest lifetime so far reported for AlxGa1?xN-based QWs emitting below 270 nm, indicating the suppression of nonradiative recombination, the dominant recombination process at RT. Compared with planar QWs without macrosteps, the emission internal quantum efficiency estimated by photoluminescence spectroscopy is improved approximately by two orders of magnitude under a weak excitation condition. Consequently, AlxGa1?xN-based MS-QWs are promising structures for highly efficient ultraviolet emitters.
关键词： AlGaN,macrosteps,nonradiative recombination,quantum wells
更新于2025-09-10 09:29:36
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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz2018) - Nagoya, Japan (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Spectroscopy of Temperature-Driven Single Valley Dirac Fermions in HgTe/CdHgTe Quantum Wells
摘要： We report on the temperature-dependent magneto-absorption and magnetotransport spectroscopy of HgTe/CdHgTe quantum wells above the critical well thickness dc. Our results, obtained in magnetic fields up to 16 T and temperature range from 1.7 to 150 K, clearly indicate a change in the band-gap energy with temperature. A topological phase transition between quantum spin Hall and trivial insulator states, revealing appearance of single-valley Dirac fermions at T = 27 and 90 K for 6.5 and 8 nm QWs respectively, was clearly observed in our magnetospectroscopy measurements.
关键词： magneto-absorption,topological phase transition,Dirac fermions,HgTe/CdHgTe quantum wells,magnetotransport spectroscopy
更新于2025-09-10 09:29:36