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THz Wave Emission From ZnTe Nano-Colloidal Aqueous Dispersion Irradiated by Femtosecond Laser
摘要： THz wave emission from ZnTe nano-colloidal aqueous dispersion flow (the particle size is 5-nm in diameter, the flow thickness is 17 μm) with two different particle densities (1.60 mmol/L and 1.07 mmol/L) was measured by time-domain spectroscopy (TDS) under femtosecond laser irradiation (>35 fs/transform-limited, 800 nm, horizontally-polarized, 0.5 kHz) in air. Intensity increase and peak shift in the TDS signal wave-form if compared with distilled water indicate that THz wave emission is induced in ZnTe nano-particles in the aqueous dispersion.
关键词： Terahertz,femtosecond laser,ZnTe nano-colloid
更新于2025-09-23 15:21:01
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Combined Optical-Electrical Optimization of Cd1a??xZnxTe/Silicon Tandem Solar Cells
摘要： Although the fundamental limits have been established for the single junction solar cells, tandem configurations are one of the promising approaches to surpass these limits. One of the candidates for the top cell absorber is CdTe, as the CdTe photovoltaic technology has significant advantages: stability, high performance, and relatively inexpensive. In addition, it is possible to tune the CdTe bandgap by introducing, for example, Zn into the composition, forming Cd1?xZnxTe alloys, which can fulfill the Shockley–Queisser limit design criteria for tandem devices. The interdigitated back contact (IBC) silicon solar cells presented record high efficiencies recently, making them an attractive candidate for the rear cell. In this work, we present a combined optical and electrical optimization of Cd1?xZnxTe/IBC Si tandem configurations. Optical and electrical loss mechanisms are addressed, and individual layers are optimized. Alternative electron transport layers and transparent conductive electrodes are discussed for maximizing the top cell and tandem efficiency.
关键词： ZnTe,IBC silicon cell,c-Si,photovoltaic cell,CdTe,tandem cell,CdZnTe
更新于2025-09-23 15:19:57
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Dielectric Response of ZnTea??Ti/Al Schottky Junctions with CdTe Quantum Dots Studied by Impedance Spectroscopy
摘要： The electrical properties of ZnTe–Ti/Al Schottky junctions were investigated by the impedance spectroscopy (IS) method. Current-voltage (I-V) and capacitance-voltage (C-V) measurements were also performed. The studied samples were the CdTe quantum dot structures embedded in ZnTe matrix and a reference ZnTe sample without quantum dots. C-V characteristics confirmed the presence of quantum dots (QDs) in the structures. Electric modulus and impedance data were analyzed. IS studies proved that long-range conductivity governs the relaxation processes in the junctions. For both samples, the data were fitted with a simple RC circuit composed of a depletion layer capacitance in parallel with bulk resistance and a series resistance of contacts. The activation energy of the relaxation process observed for the reference sample obtained from the Arrhenius plot of the resistance, imaginary impedance, and electric modulus equals 0.4 eV at zero bias. For the quantum dot sample, the value of activation energy determined with the help of the same methods equals 0.2 eV. In conclusion, it was assumed that the relaxation processes for the reference sample are attributed to the trap present in ZnTe host material, whereas those observed for the QD structure are assigned to the deep level associated with defects located close to the QDs created during their growth.
关键词： quantum dots,defects,impedance spectroscopy,CdTe,ZnTe
更新于2025-09-23 15:19:57
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Microstructural Characterization of Defects and Chemical Etching for HgCdSe/ZnTe/Si (211) Heterostructures
摘要： In this work, transmission electron microscopy has been used to investigate HgCdSe/ZnTe/Si (211) heterostructures grown by molecular beam epitaxy and to study the effects of chemical etchants for measurements of defect density in the HgCdSe epilayers. Both ZnTe/Si and HgCdSe/ZnTe interfaces were decorated with {111}-type stacking faults inclined at angles of ~19° or ~90° with respect to the interface plane. Similar stacking faults were also present in the upper regions of the HgCdSe films. High-resolution imaging and Fourier image analysis revealed dislocations, mostly with a Burgers vector, at both ZnTe/Si and HgCdSe/ZnTe interfaces. Etching solutions based on different combinations of nitric acid, hydrochloric acid and lactic acid were tried in attempts to identify an etchant that provided one-to-one correspondence between etch pits and defects in the HgCdSe layer. Focused-ion-beam milling and transmission electron microscopy were used to prepare site-specific cross-section samples from across the etch pits. However, many defects in regions surrounding the etch pits were unaffected by the various different etchants.
关键词： dislocations,etch pits,HgCdSe (211),alternative substrates,ZnTe
更新于2025-09-23 15:19:57
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Insights into the role of interface modification in performance enhancement of ZnTe:Cu contacted CdTe thin film solar cells
摘要： CdTe has become a leading contributor in the thin-film photovoltaic market. A suitable back contact is still one of the most crucial issues to realize efficient CdTe thin film solar cells. Herein, we intensively studied the mechanisms of interfacial modification and device performance enhancement for the representative ZnTe:Cu back contact structure. It’s found that, in spite the as-deposited ZnTe:Cu buffer could reduce the contact barrier, the device performance is still limited by the increased defect-related recombination. A controlled heat treatment process is proved to be effective in alleviating the recombination loss at the back contact. Detailed characterizations demonstrate that the CdTe/ZnTe:Cu interface reaction happens and the interfacial composition is modified during the heat treatment process, which optimize the interfacial chemical states and band alignment. The improved interfacial properties decrease the defect-related recombination and promote the holes transport, and consequently improve the device efficiency greatly.
关键词： ZnTe:Cu,Recombination,CdTe,Solar cell,Interface modification
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - CdCl <sub/>2</sub> Activation of the ZnTe:As Back Contact Layer in CdTe Thin Film Solar Cells, Employing a CdS Sacrificial Layer
摘要： Incorporating ZnTe:As back contact to CdTe thin film solar cells is an attractive alternative to Cu treated ZnTe back contacts, getting rid of Cu diffusion and subsequent long term stability issues. However, the Zn loss by the formation of volatile ZnCl2 during CdCl2 deposition heat treatment for the back-contact activation remains a challenge. The aim of this work is to develop an effective activation process for ZnTe:As back contacts, which is expected to improve CdTe solar cell efficiencies. To minimize Zn loss, a thin CdS sacrificial cap layer was evaluated which was deposited on ZnTe:As via MOCVD prior to the contact layer activation step.
关键词： ZnTe back contact,photovoltaic cells,CdS sacrificial layer,CdTe,Thin films
更新于2025-09-19 17:13:59
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The electronic and optical properties of an exciton, biexciton and charged excitons in CdSe/CdTe-based multi-shell type-II quantum dot nanocrystals
摘要： It has been recently reported that multi-shell type-II quantum dot nanocrystals (QDNCs) have higher quantum yields. Besides these higher quantum yields of multi-shell type-II QDNCs, additional second layer has been a critical influence on the formation mechanisms of the excitonic structures. Understanding of bound and unbound cases of the excitonic structures in multi-shell type-II QDNCs gives some important information for applications. In this study, we have investigated the electronic and optical properties of a single exciton (X), biexciton (XX), and positively and negatively charged excitons ( ??+ and ??? ) in CdSe/CdTe-based multi-shell type-II QDNCs. In the study, three different structure compositions, i.e., CdSe/CdTe, CdSe/CdTe/CdS, and CdSe/CdTe/ZnTe, have been considered. We have observed that CdS and ZnTe materials have drastically changed the electronic and optical properties of the bare CdSe/CdTe type-II QDNCs.
关键词： Exciton,CdS,Biexciton,CdSe/CdTe,Charged excitons,ZnTe,Quantum dot nanocrystals,Type-II
更新于2025-09-12 10:27:22
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Properties of Arsenic–Doped ZnTe Thin Films as a Back Contact for CdTe Solar Cells
摘要： As-doped polycrystalline ZnTe layers grown by metalorganic chemical vapor deposition (MOCVD) have been investigated as a back contact for CdTe solar cells. While undoped ZnTe ?lms were essentially insulating, the doped layers showed signi?cant rise in conductivity with increasing As concentration. High p-type carrier densities up 4.5 × 1018 cm?3 was measured by the Hall-e?ect in heavily doped ZnTe:As ?lms, displaying electrical properties comparable to epitaxial ZnTe single crystalline thin ?lms in the literature. Device incorporation with as-deposited ZnTe:As yielded lower photovoltaic (PV) performance compared to reference devices, due to losses in the open-circuit potential (VOC) and ?ll factor (FF) related to reducing p-type doping density (NA) in the absorber layer. Some minor recovery observed in absorber doping following a Cl-free post–ZnTe:As deposition anneal in hydrogen at 420 ?C contributed to a slight improvement in VOC and NA, highlighting the signi?cance of back contact activation. A mild CdCl2 activation process on the ZnTe:As back contact layer via a sacri?cial CdS cap layer has been assessed to suppress Zn losses, which occur in the case of standard CdCl2 anneal treatments (CHT) via formation of volatile ZnCl2. The CdS sacri?cial cap was e?ective in minimising the Zn loss. Compared to untreated and non-capped, mild CHT processed ZnTe:As back contacted devices, mild CHT with a CdS barrier showed the highest recovery in absorber doping and an ~10 mV gain in VOC, with the best cell e?ciency approaching the baseline devices.
关键词： solar cells,CdTe,metalorganic chemical vapor deposition (MOCVD),ZnTe:As back contact,thin ?lms
更新于2025-09-11 14:15:04
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Fluorescence detection of Escherichia coli on mannose modified ZnTe quantum dots
摘要： Rapid detection and identification of Escherichia coli (E.coli) is essential to prevent its quickly spread. In this study, a novel fluorescence probe based on ZnTe quantum dots (QDs) modified by mannose (MAN) had been prepared for the determination of E.coli. The results showed that the obtained QDs showed excellent selectivity toward E.coli, and presented a good linearity in range of 1.0 × 105~1.0 × 108 CFU/mL. The optimum fluorescence intensity for detecting E.coli was found to be at pH 7.0 with a temperature of 25 oC and incubation time of 20 min. Under these optimum conditions, the detection limit of E.coli was 4.6 × 104 CFU/mL. The quenching was discussed to be a static quenching procedure, which was proved by the quenching efficiency of QDs decreased with the temperature increasing.
关键词： Fluorescence intensity,Mannose,ZnTe quantum dots,Probe,Escherichia coli
更新于2025-09-11 14:15:04
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Growth of large-size high-quality ZnTe bulk crystals by traveling solvent melting zone method
摘要： ZnTe crystal is a promising electro-optical crystal materials applied for THz generation and detection. However, there is still a big challenge to obtain large sized high quality ZnTe crystals. In this work, large sized ZnTe bulk crystals with Φ30 mm × 150 mm were grown by the traveling solvent melting zone (TSMZ) method. With the characterization of the optical and electrical properties of as-grown ZnTe crystals, the band gap (2.22 eV), high IR transmittance (around 60%), high resistivity (3.5×103 ??cm), low density (1.3×105 cm-2) and small sizes (3μm - 5 μm) of Te inclusions in ZnTe crystals, low etch pit densities (1.5×105 cm-2), high peak intensity to FWHM ratio (2.5×104) of the LO peak in the Raman spectra were obtained. Furthermore, the THz transmission spectra was measured and the maximum transmittance is more than 40% at the range of 0.3 - 3THz. Based on these results, high quality and large aspect ratio ZnTe bulk crystals can be obtained by the TSMZ technique. Our work has greatly facilitated the application of ZnTe crystals in THz device.
关键词： terahertz,ZnTe,traveling solvent melting zone,electro-optical materials
更新于2025-09-10 09:29:36