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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) - Wet-Chemically Textured Ultra-Thin GaAs Solar Cells with Dielectric/Metal Rear Mirrors
摘要： The rear-side contact layer of ultra-thin GaAs solar cells was textured using a simple, one-step wet chemical approach. A ZnS/Ag double layer was conformally deposited to function as a diffusive rear mirror. Local Ohmic contact points provided electrical contact directly to the Ag. The textured solar cells were compared with planar reference cells fabricated on the same wafer and a clear enhancement of long-wavelength quantum efficiency and short-circuit current was observed in the textured cells. Both architectures showed FF > 80% and VOC > 1 V. Additionally, the rear-side texture increases the external luminescent efficiency by enhancing outcoupling of luminescence.
关键词： light trapping,ultra-thin GaAs solar cells,dielectric mirror,wet etching
更新于2025-09-23 15:19:57
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Development of additive-assisted Ag-MACE for multicrystalline black Si solar cells
摘要： The uniform distribution of silver nanoparticles on the surfaces of diamond-wire sawn multicrystalline silicon (mc-Si) is critical for the texturing of mc-Si by the Ag metal-assisted chemical etching method (Ag-MACE). In this study, an additive containing alkylphenol polyoxyethylene is developed to improve the Ag-MACE process. It enables an even deposition of the silver nanoparticles over the surface of the silicon wafer, so that the entire wafer surface can be uniformly textured with nanostructures. The experimental results show that the additive improves the appearance and performance of solar cells, including their reflectivity, efficiency, internal quantum efficiency and external quantum efficiency. Mass-produced mc-Si solar cells textured using Ag-MACE with this additive have achieved a maximum efficiency of 19.51%, compared with an efficiency of 19.16% for cells fabricated without the additive.
关键词： metal-assisted chemical etching,additive,diamond wire saw,uniform textures,solar cell,multicrystalline silicon
更新于2025-09-23 15:19:57
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Controllable Patterning of Hybrid Silicon Nanowire and Nanohole Arrays by Laser Interference Lithography
摘要： Metal-assisted chemical etching (MACE) is a cost-effective method to fabricate Si nanostructures including silicon nanowires (SiNWs) and silicon nanoholes (SiNHs). However, the preparation of metallic template for MACE would require complex experimental conditions including strict cleaning process and multiple steps. In our study, we applied superlens-enhanced laser interference lithography to directly fabricate complicated metallic patterns and then used MACE to obtain hybrid SiNW and SiNH arrays. Ag films were firstly deposited on Si substrates, and then a 1064 nm high power laser source was utilized to generate two-beam interference electric fields. Since Ag molecules are very sensitive to any input energy change, they tend to break up or aggregate and form different Ag patterns which have a specific energy threshold in order to lower its free energy. By manipulating the distribution of input electric field, we are able to obtain complicated metallic patterns and their corresponding Si nanostructures with feature sizes that range from tens of nanometers to several micrometers.
关键词： silicon nanowires and silicon nanoholes,silicon nanostructures,nanofabrication,metal-assisted chemical etching
更新于2025-09-23 15:19:57
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Controllable photon energy deposition efficiency in laser processing of fused silica by temporally shaped femtosecond pulse: Experimental and theoretical study
摘要： Photon energy deposition plays a crucial role in femtosecond laser irradiation followed by chemical etching processing, which is an emerging technique for the better control of micro/nano structures on fused silica. In this study, we have experimentally and theoretically studied the controllable photon energy deposition in laser irradiation of fused silica by temporally shaped femtosecond laser pulse trains. The experimental result shows that the photon energy deposition efficiency could be either reduced or enhanced by adjusting the total fluence of shaped pulse trains. Furthermore, the sub-pulse interval and intensity ratio of temporally shaped pulse trains were revealed to play a critical role in photon energy deposition. The corresponding experimental observations are qualitatively explained by a plasma model that considers the free electron generation processes and corresponding feedback on the photon energy deposition.
关键词： Photon energy deposition,Femtosecond laser,Temporally shaped pulse,Chemical etching,Fused silica
更新于2025-09-23 15:19:57
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Surface micromachining on a polymethylmethacrylate substrate using visible laser-induced backside wet etching with a KMnO <sub/>4</sub> solution as an absorber
摘要： In this paper, the authors report a method for continuous trench micromachining on polymethylmethacrylate (PMMA). Visible laser-induced backside wet etching (v-LIBWE) on PMMA using a potassium permanganate (KMnO4)-based absorber liquid was studied. PMMA is widely used in microfluidic devices for chemical and biological applications. Conventional micromachining of channels in the PMMA substrate using CO2 lasers achieves the smallest feature of approximately 85 μm. In this study, a continuous 12 μm-wide trench etching on PMMA was achievable by v-LIBWE using a 532 nm nanosecond pulsed laser. The etching threshold is ～10 J/cm2, which corresponds to the average power of 58 mW for the repetition rate of 10 kHz. The authors also determined that the lowest scanning speed of 2 mm/s was necessary for the v-LIBWE of PMMA to generate the crack-free surface. Our study provides a new perspective and a convenient approach for the micromachining of the polymer substrate using v-LIBWE.
关键词： PMMA,potassium permanganate (KMnO4),visible LIBWE (v-LIBWE),laser etching
更新于2025-09-23 15:19:57
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Fabrication of Random Microlens Array for Laser Beam Homogenization with High Efficiency
摘要： The miniaturized and integrated microlens array (MLA) can effectively achieve the beam homogenization, compactness and miniaturization of laser systems. When the high-coherence laser beam is homogenized by means of using the MLA, interference fringes will occur in the homogenized light spot due to the periodicity of the MLA, which seriously affects the uniformity of the homogenized light spot. To solve this problem, a novel random microlens array (rMLA) structure was proposed for the purpose of achieving beam homogenization. The coherence in the homogenization process is suppressed by means of breaking the periodicity of the MLA. The homogenized light spot with a high energy utilization is then obtained accordingly. In the fabrication process, a clever method of combining chemical etching with lithography technology is performed to fabricate a honeycomb rMLA and a rectangular rMLA. The experimental results show that the energy utilization rate of the two types of the rMLAs is about 90%, and the uniformity of the homogenized light spots generated by the honeycomb rMLA and the rectangular rMLA are more than 80% and 85%, respectively. Meanwhile, fully cost-effective fabrication is possible to be realized.
关键词： random microlens array,beam homogenization,laser,chemical etching
更新于2025-09-23 15:19:57
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Development of All-Diamond Scanning Probes Based on Faraday Cage Angled Etching Techniques
摘要： We are proposing a novel fabrication method for single crystal diamond scanning probes for atomic force microscopy (AFM), exploiting Faraday cage angled etching (FCAE). Common, oxygen-based, inductively coupled plasma (ICP) dry etching processes for diamond are limited with respect to the achievable geometries. The fabrication of freestanding micro- and nanostructures is therefore challenging. This is a major disadvantage for several application fields e.g., for realizing scanning magnetometry probes based on nitrogen vacancy (NV) centres and capable of measuring magnetic fields at the nanoscale. Combining a planar design with FCAE and state-of-the-art electron beam lithography (EBL) yields a reduction of process complexity and cost compared to the established fabrication technology of micro-opto-mechanical diamond devices. Here, we report on the direct comparison of both approaches and present first proof-of-concept planar-FCAE-prototypes for scanning probe applications.
关键词： Faraday cage angled etching,scanning magnetometry,atomic force microscopy,diamond scanning probes,nitrogen vacancy centres
更新于2025-09-23 15:19:57
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Changes in the Photoluminescence of Monolayer and Bilayer Molybdenum Disulfide during Laser Irradiation
摘要： Various postsynthesis processes for transition metal dichalcogenides have been attempted to control the layer number and defect concentration, on which electrical and optical properties strongly depend. In this work, we monitored changes in the photoluminescence (PL) of molybdenum disulfide (MoS2) until laser irradiation generated defects on the sample flake and completely etched it away. Higher laser power was required to etch bilayer MoS2 compared to monolayer MoS2. When the laser power was 270 μW with a full width at half-maximum of 1.8 μm on bilayer MoS2, the change in PL intensity over time showed a double maximum during laser irradiation due to a layer-by-layer etching of the flake. When the laser power was increased to 405 μW, however, both layers of bilayer MoS2 were etched all at once, which resulted in a single maximum in the change of PL intensity over time, as in the case of monolayer MoS2. The dependence of the etching pattern for bilayer MoS2 on laser power was also reflected in position changes of both exciton and trion PL peaks. The subtle changes in the PL spectra of MoS2 as a result of laser irradiation found here are discussed in terms of PL quantum efficiency, conversion between trions and excitons, mean interatomic spacing, and the screening of Coulomb interaction.
关键词： photoluminescence,defects,etching,laser irradiation,molybdenum disulfide
更新于2025-09-23 15:19:57
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Thin-film flip-chip UVB LEDs realized by electrochemical etching
摘要： We demonstrate a thin-?lm ?ip-chip (TFFC) light-emitting diode (LED) emitting in the ultraviolet B (UVB) at 311 nm, where substrate removal has been achieved by electrochemical etching of a sacri?cial Al0:37Ga0:63N layer. The electroluminescence spectrum of the TFFC LED corresponds well to the as-grown LED structure, showing no sign of degradation of structural and optical properties by electrochemical etching. This is achieved by a proper epitaxial design of the sacri?cial layer and the etch stop layers in relation to the LED structure and the electrochemical etch conditions. Enabling a TFFC UV LED is an important step toward improving the light extraction ef?ciency that limits the power conversion ef?ciency in AlGaN-based LEDs.
关键词： Thin-film flip-chip,AlGaN,light extraction efficiency,UVB LEDs,electrochemical etching
更新于2025-09-23 15:19:57
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Linear-nonlinear optical, dielectric and surface microscopic investigation of KH2PO4 crystal to uncover the decisive impact of dopant glycine
摘要： Present investigation has been started to perform the comparative study of pure and glycine doped KH2PO4 (KDP) single crystals grown by most commercial slow solvent evaporation technique. The grown crystals were subjected to single crystal X-ray diffraction analysis to determine their structural parameters. The linear optical studies of pure and glycine doped KDP crystal have been undertaken within 200 nm to 1100 nm wavelength range by means of UV-Vis studies. The enhancement in second harmonic generation (SHG) ef?ciency of glycine doped KDP crystal has been determined using a standard Kurtz-Perry powder test. The dielectric measurements have been carried out to explore the impact of glycine dopant on dielectric constant and dielectric loss of KDP crystal. The surface growth habitat and etch pit density of glycine doped KDP crystal have been evaluated using the results of microscopic etching studies. In light of obtained results the suitability of glycine doped KDP crystal for device applications has been discussed.
关键词： optical studies,etching studies,crystal growth,dielectric studies,nonlinear optical materials
更新于2025-09-23 15:19:57