LT) can be achieved for weakly absorbed photons with energies close to the absorption edge of silicon. [ 15 ] These properties of b-Si are particularly useful for photovoltaic applications.The limiting effi ciency of a solar cell is given by the detailed balance of absorption and radiative recombination [ 16 ] and by nonradiative processes like Auger-and impurity recombination. [17][18][19] b-Si can help to approach those limits in two ways. On the one hand b-Si improves the coupling of light into the solar cell and the absorption of near band edge photons. This in turn increases the short circuit current and on a logarithmic scale also the open circuit voltage. On the other hand, due to excellent light-trapping properties b-Si might also allow reducing the solar cell thickness substantially below 100 µm while sustaining a high light absorption. This reduces nonradiative bulk recombination losses that scale linearly with the solar cell thickness [ 17,18 ] and hence, increases the open-circuit voltage. Of course, reducing the solar cell thickness also increases the cost effi ciency. Decreasing the amount of required silicon feedstock is a major industry concern as can be seen by the growing interest in kerf-free crystalline silicon solar cell technologies. [20][21][22] Unfortunately, besides bulk effects, surface recombination imposes a very critical limit to the solar This article presents an overview of the fabrication methods of black silicon, their resulting morphologies, and a quantitative comparison of their optoelectronic properties. To perform this quantitative comparison, different groups working on black silicon solar cells have cooperated for this study. The optical absorption and the minority carrier lifetime are used as benchmark parameters. The differences in the fabrication processes plasma etching, chemical etching, or laser processing are discussed and compared with numerical models. Guidelines to optimize the relevant physical parameters, such as the correlation length, optimal height of the nanostructures, and the surface defect densities for optoelectronic applications are given.
The potential of particle therapy due to focused dose deposition in the Bragg peak has not yet been fully realized due to inaccuracies in range verification. The purpose of this work was to correlate the Bragg peak location with target structure, by overlaying the location of the Bragg peak onto a standard ultrasound image. Pulsed delivery of 50 MeV protons was accomplished by a fast chopper installed between the ion source and the cyclotron inflector. The chopper limited the train of bunches so that 2 Gy were delivered in [Formula: see text]. The ion pulse generated thermoacoustic pulses that were detected by a cardiac ultrasound array, which also produced a grayscale ultrasound image. A filtered backprojection algorithm focused the received signal to the Bragg peak location with perfect co-registration to the ultrasound images. Data was collected in a room temperature water bath and gelatin phantom with a cavity designed to mimic the intestine, in which gas pockets can displace the Bragg peak. Phantom experiments performed with the cavity both empty and filled with olive oil confirmed that displacement of the Bragg peak due to anatomical change could be detected. Thermoacoustic range measurements in the waterbath agreed with Monte Carlo simulation within 1.2 mm. In the phantom, thermoacoustic range estimates and first-order range estimates from CT images agreed to within 1.5 mm.
35 words): An overview and comparison of different fabrication methods of black silicon is presented. Guidelines to optimize relevant parameters such as spatial frequencies and surface defect densities for optoelectronic applications such as photovoltaics will be given. Summary:The potential of silicon surfaces structured in the micro-and nanometer regime are widely known, e.g. in photovoltaic (PV) crystalline silicon (c-Si) solar cells [1][2], watersplitting by photo-electrochemical-catalysis (PEC) [3], phododiods [4], terahertz emitters[5], highly sensitive optical[6] and chemical detection devices [7], amongst many others. Black silicon offers extraordinary and broadband antireflection properties [8]. Additionally, strong randomizing light-trapping is achieved for weakly absorbed photons close to the band edge of c-Si, i.e. light trapping [9]. The enlarged area for 3-D structured p/n-junctions might be advantageous for charge carrier separation. But due to the strongly enlarged surface and a usually high surface defect density black silicon nanostructures exhibit rather low electronic surface quality leading to strong surface recombination. This drawback limits the performance of potential devices [10], [11]. Therefore, effective surface passivation is essential for nanostructured silicon and investigations to find a well suited passivation scheme are going on ever since b-Si has been used for electro-optical devices. In this work, different black silicon fabrication methods are compared. Investigated are the resulting morphologies, as well as optical and electronic properties. Different groups working on black silicon have cooperated for this study. As benchmark parameters, we used the optical absorption and the minority carrier lifetime after the passivation of the samples with thermal-atomic layer deposited Al2O3 [12]. The differences of the obtained black silicon samples fabricated by different proceesses, such as plasma etching, chemical etching or laser processing, are discussed. Based on our findings, we will give guidelines to optimize the relevant physical parameters, e.g. the spatial frequencies and the surface defect densities for optoelectronic applications. PTu2C.2.pdf
Experimentally determined reduction of both ohmic and mass transport overpotential due to femtosecond laser-induced surface structuring of titanium-based porous transport layers at the interface to the catalyst layer.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.