Resonant optical nanoantennas hold great promise for applications in physics and chemistry. Their operation relies on their ability to concentrate light on spatial scales much smaller than the ...wavelength. In this work, we mechanically tune the length and gap between two triangles comprising a single gold bow-tie antenna by precise nanomanipulation with the tip of an atomic force microscope. At the same time, the optical response of the nanostructure is determined by means of dark-field scattering spectroscopy. We find no unique single 'antenna resonance'. Instead, the plasmon mode splits into two dipole resonances for gap sizes on the order of a few tens of nanometres, governed by the full three-dimensional shape of the antenna arms. This result opens the door to new nano-optomechanical devices, where mechanical changes on the nanometre scale control the optical properties of artificial structures.
Lomer dislocations at small-angle grain boundaries in multicrystalline silicon solar cells have been identified as responsible for the dominating inherent dark current losses. Resulting efficiency ...losses have been quantified by dark lock-in thermography to be locally up to several percent absolute, reducing the maximum power of the cells. By electron beam induced current measurements and scanning transmission electron microscopy investigations, it is revealed that the strengths of the dark current losses depend on the density of Lomer dislocations at the small-angle grain boundaries.
Material induced inherent efficiency losses of multicrystalline silicon solar cells have been investigated across all scales from the solar cell down to the atomic structure of the responsible ...crystallographic defects. Material inherent efficiency losses can be attributed to local increased dark current, which is found at recombination active small angle grain boundaries and accounts to several per-cent absolute. Aone-to-one correlation between the density of Lomer dislocations and the strength of the recombination activity of small angle grain boundaries is found by electron-beam induced current measurements and scanning transmission electron microscope investigations. The increased recombination activity of Lomer dislocations is attributed to their immobile nature, which favors contamination by impurities.
Phosphorus diffusion gettering of multicrystalline silicon solar cell materials generally fails to produce material with minority-carrier lifetimes that approach that of gettered monocrystalline ...wafers, due largely to higher levels of contamination with metal impurities and a higher density of structural defects. Higher gettering temperatures should speed the dissolution of precipitated metals by increasing their diffusivity and solubility in the bulk, potentially allowing for improved gettering. In this paper, we investigate the impact of gettering at higher temperatures on low-purity multicrystalline samples. To analyze the gettering response, we measure the spatially resolved lifetime and interstitial iron concentration by microwave photoconductance decay and photoluminescence imaging, and the structural defect density by Sopori etching and large-area automated quantification. Higher temperature phosphorus diffusion gettering is seen to improve metal-limited multicrystalline materials dramatically, especially in areas of low etch pit density. In areas of high as-grown dislocation density in the multicrystalline materials, it appears that higher temperature phosphorus diffusion gettering reduces the etch pit density, but leaves higher local concentrations of interstitial iron, which degrade lifetime.
Here, two B‐doped Cz‐grown Si materials with different Al concentrations are investigated concerning the long‐term behavior of excess charge carrier lifetime under injection at elevated temperature. ...By determining the defect density and the surface saturation current density, a delay in regeneration and a delay in the onset of surface‐related degradation is found in the material containing an order of magnitude more Al. Investigations under constant excess carrier concentration reveal that the effect of the delay is still significant, but less pronounced compared with constant generation conditions, so the effect causing the delay seems to be injection dependent. The findings can be explained by the higher activation energy for the splitting of Al−H pairs compared with splitting of B−H pairs, which might cause a delayed release in H from the dopant H configuration. Assuming that regeneration depends on this released H, the delay in regeneration can be explained by this model.
The influence of addition of aluminum in boron‐doped Cz‐Si on long‐term behavior of excess charge carrier lifetime is investigated. A delay in regeneration and delay in the onset of surface‐related degradation are found in the material containing more Al. The findings could be explained by the higher activation energy for splitting of Al−H pairs compared with splitting of B−H pairs.
Herein, the effects of gettering, temperature, dopant concentration, and metal contamination on the etch pit density (EPD) of an mc‐Si material are studied. It is demonstrated that there is a ...reduction of EPD after gettering that is independent for varying etchants, thereby confirming the physical nature of this effect. The EPD analysis of wafers that are gettered on one wafer side, results in different EPD values for the two wafer sides. This finding constrains the possibilities for mechanisms of EPD reduction. The combined evidence of the experiments presented here supports the hypothesis that EPD reduction happens because the defect etching process for impurity‐lean dislocations is different from dislocations decorated with impurities.
In this work, the influence of highly doped layers on the hydrogen in-diffusion into silicon from hydrogen-rich silicon nitride is investigated. Hydrogen in the crystalline silicon bulk of wafers ...with and without highly doped layers present was examined in solar cell-like structures by resistivity measurements for quantification of BH-pair dynamics. Hydrogen diffusion through phosphorus- and boron-doped Float-Zone samples without highly doped layers and with p+- respectively n+-layers was determined via secondary ion mass spectrometry. Therefore, deuterium concentration in an amorphous silicon layer on the backside was measured. This experiment shows an up to threefold increase of deuterium concentration in the amorphous layer for samples with highly doped layers present. A possible explanation of this observation is given by simulations.
•Influence of highly doped layers on H in-diffusion.•BH-pair dynamics in samples with and without highly doped layers.•SIMS data of D diffusing through highly doped layers and bulk c-Si.•Simulations of H-species in samples with n+-p-n+ structure after firing.
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