Improved homogeneity of microcrystalline absorber layer in thin-film silicon tandem solar cells

Smirnov, Vladimir; Das, Chandan; Melle, Thomas; Lambertz, Andreas; Hülsbeck, Markus; Carius, R.; Finger, F.

doi:10.1016/j.mseb.2008.10.050

Cited by 21 publications

(14 citation statements)

References 15 publications

(22 reference statements)

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“…The increase in I c is visible for both the 1:200 series between r CO 2 0.5 to 1 and for the 1:500 series between r CO 2 of two and three even for layers of several hundreds of nanometers. Previous studies [22][23][24][25][26] have already shown the critical dependence of the film properties on the "substrate"-layer morphology especially in the transition region between a-Si:H and lc-Si:H growth. These studies show that layers deposited in the transition region grow completely amorphous or microcrystalline in dependence on the crystallinity of the "substrate" layer.…”

Section: Crystallinitymentioning

confidence: 99%

Hydrogenated amorphous silicon oxide containing a microcrystalline silicon phase and usage as an intermediate reflector in thin-film silicon solar cells

Lambertz

Grundler

Finger

2011

Journal of Applied Physics

108

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To further improve the stability of amorphous/microcrystalline silicon (a-Si:H/μc-Si:H) tandem solar cells, it is important to reduce the thickness of the a-Si:H top cell. This can be achieved by introduction of an intermediate reflector between the a-Si:H top and the μc-Si:H bottom cell which reflects light back into the a-Si:H cell and thus, increases its photocurrent at possibly reduced thickness. Microcrystalline silicon oxide (μc-SiOx:H) is used for this purpose and the trade-off between the material’s optical, electrical and structural properties is studied in detail. The material is prepared with plasma enhanced chemical vapor deposition from gas mixtures of silane, carbon dioxide and hydrogen. Phosphorus doping is used to make the material highly conductive n-type. Intermediate reflectors with different optical and electrical properties are then built into tandem solar cells as part of the inner n/p-recombination junction. The quantum efficiency and the reflectance of these solar cells are evaluated to find optical gains and losses due to the intermediate reflector. Suitable intermediate reflectors result in a considerable increase in the top cell current density which allows a reduction of the a-Si:H top cell thickness of about 40% for a tandem cell while keeping the current density of the device constant.

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Section: Crystallinitymentioning

confidence: 99%

Hydrogenated amorphous silicon oxide containing a microcrystalline silicon phase and usage as an intermediate reflector in thin-film silicon solar cells

Lambertz

Grundler

Finger

2011

Journal of Applied Physics

108

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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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“…In general, PECVD-inherent process drifts 19,21 and the conical evolution of the crystallites 1,9,22 for low Raman crystallinities impede a homogeneous absorber layer growth in the narrow deposition window close to 60%-70%. 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.…”

Section: Introductionmentioning

confidence: 99%

“…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%

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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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Improved homogeneity of microcrystalline absorber layer in thin-film silicon tandem solar cells

Cited by 21 publications

References 15 publications

Hydrogenated amorphous silicon oxide containing a microcrystalline silicon phase and usage as an intermediate reflector in thin-film silicon solar cells

Hydrogenated amorphous silicon oxide containing a microcrystalline silicon phase and usage as an intermediate reflector in thin-film silicon 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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