Gradient etching of silicon-based thin films for depth-resolved measurements: The example of Raman crystallinity

Thin films containing SiO 2 nanoparticles and a TiO 2 binder were prepared by sol-gel processing; their transparency and haze were characterized. By applying additional SiO 2 films the surface of these scattering layers was smoothened. This procedure improved the microstructure of aluminum-doped zinc oxide and a-Si:H/lcSi:H subsequently deposited by vapor phase deposition. The electrical properties and performance of the resulting thin film solar cells were characterized. Based on these results the proof of concept is provided for the application of sol-gel derived scattering layers in thin film photovoltaics.

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“…A spot size of 50 9 1 lm 2 was illuminated by 250 lW. The method of determining the crystalline volume fraction is described elsewhere [25,26].…”

Section: Materials Characterizationmentioning

confidence: 99%

SiO2–TiO2 scattering layers prepared by sol–gel processing for light management in thin film solar cells

Hegmann

Jahn

Schönau

et al. 2015

J Sol-Gel Sci Technol

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“…21 Samples were characterized either by a laser beam (k 5 532) directed on the as-produced sample, or, for selected samples, the Raman intensity ratio depth profile of the structure of the intrinsic absorber layer along the growth axis was determined by a gradient etching method (k 5 488 nm). 22,23 Here, Raman scattering measurements were carried out on slantwise etched craters through the solar cell structure. Solar cells were characterized by current-voltage (J-V) measurements at standard test conditions (AM 1.5 G, 100 mW/cm 2 , 25°C) illumination using a double source (Class A) AM 1.5 sun simulator.…”

Section: B Characterization Of Materials and Solar Cellsmentioning

confidence: 99%

a-Si:H/µc-Si:H tandem junction based photocathodes with high open-circuit voltage for efficient hydrogen production

et al. 2014

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Thin film silicon tandem junction solar cells based on amorphous silicon (a-Si:H) and microcrystalline silicon (lc-Si:H) were developed with focus on high open-circuit voltages for the application as photocathodes in integrated photoelectrochemical cells for water electrolysis. By adjusting various parameters in the plasma enhanced chemical vapor deposition process of the individual lc-Si:H single junction solar cells, we showed that a-Si:H/lc-Si:H tandem junction solar cells exhibit open-circuit voltage over 1.5 V with solar energy conversion efficiency of 11% at a total silicon layer thickness below 1 lm. Our approach included thickness reduction, controlled SiH 4 profiling, and incorporation of intrinsic interface buffer layers. The applicability of the tandem devices as photocathodes was evaluated in a photoelectrochemical cell. The a-Si:H/lc-Si:H based photocathodes exhibit a photocurrent onset potential of 1.3 V versus RHE and a short-circuit photocurrent of 10.0 mA/cm 2 . The presented approach may provide an efficient and low-cost pathway to solar hydrogen production.

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“…21 To achieve these Raman crystallinities throughout the entire absorber layer process settings have to be adapted during the deposition of lc-Si:H. Since this requires an adequate monitoring of the Raman crystallinity, various in-situ and ex-situ measurement techniques have been applied to characterize the lc-Si:H absorber layer deposition. [8][9][10]12,13,19,[21][22][23][24][25][26][27][28] To monitor the layer growth with adequate accuracy, diagnostic methods with high depth and temporal resolution are required. For example, in-situ ellipsometry features high surface sensitivity.…”

Section: Introductionmentioning

confidence: 99%

“…High depth resolution of the Raman crystallinity in the growth direction was achieved by KOH wet-etching or reactive ion etching. 12,21,24 Scanning the etched craters by microscopic Raman spectroscopy, the Raman crystallinity is estimated in the growth direction of the lc-Si:H film ex-situ. 24 In the present paper, we investigate the microcrystalline silicon growth by the technique of in-situ Raman spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

“…12,21,24 Scanning the etched craters by microscopic Raman spectroscopy, the Raman crystallinity is estimated in the growth direction of the lc-Si:H film ex-situ. 24 In the present paper, we investigate the microcrystalline silicon growth by the technique of in-situ Raman spectroscopy. 30 This method enables the monitoring of the Raman crystallinity during the deposition of the absorber layer.…”

Section: Introductionmentioning

confidence: 99%

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Interplay between crystallinity profiles and the performance of microcrystalline thin-film silicon solar cells studied by in-situ Raman spectroscopy

Fink

Muthmann

Mück

et al. 2015

Journal of Applied Physics

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The intrinsic microcrystalline absorber layer growth in thin-film silicon solar-cells is investigated by in-situ Raman spectroscopy during plasma enhanced chemical vapor deposition. In-situ Raman spectroscopy enables a detailed study of the correlation between the process settings, the evolution of the Raman crystallinity in growth direction, and the photovoltaic parameters η (solar cell conversion efficiency), JSC (short circuit current density), FF (fill factor), and VOC (open circuit voltage). Raman spectra were taken every 7 nm of the absorber layer growth depending on the process settings. The Raman crystallinity of growing microcrystalline silicon was determined with an absolute error of approximately ±5% for total absorber layer thicknesses >50 nm. Due to this high accuracy, inherent drifts of the Raman crystallinity profiles are resolvable for almost the entire absorber layer deposition. For constant process settings and optimized solar cell device efficiency Raman crystallinity increases during the absorber layer growth. To compensate the inhomogeneous absorber layer growth process settings were adjusted. As a result, absorber layers with a constant Raman crystallinity profile — as observed in-situ — were deposited. Solar cells with those absorber layers show a strongly enhanced conversion efficiency by ∼0.5% absolute. However, the highest FF, VOC, and JSC were detected for solar cells with different Raman crystallinity profiles. In particular, fill factors of 74.5% were observed for solar cells with decreasing Raman crystallinity during the later absorber layer growth. In contrast, intrinsic layers with favorable JSC are obtained for constant and increasing Raman crystallinity profiles. Therefore, monitoring the evolution of the Raman crystallinity in-situ provides sufficient information for an optimization of the photovoltaic parameters with surpassing depth resolution.

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Gradient etching of silicon-based thin films for depth-resolved measurements: The example of Raman crystallinity

Cited by 14 publications

References 16 publications

SiO2–TiO2 scattering layers prepared by sol–gel processing for light management in thin film solar cells

SiO2–TiO2 scattering layers prepared by sol–gel processing for light management in thin film solar cells

a-Si:H/µc-Si:H tandem junction based photocathodes with high open-circuit voltage for efficient hydrogen production

Interplay between crystallinity profiles and the performance of microcrystalline thin-film silicon solar cells studied by in-situ Raman spectroscopy

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