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

Fink, T.; Carius, R.; Gordijn, A.; Meier, Matthias; Mück, A.; Muthmann, S.

doi:10.1063/1.4936616

Journal Article

FZJ-2015-07329

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

Fink, T. (Corresponding author)FZJ* ; Muthmann, S.FZJ* ; Mück, A.FZJ* ; Gordijn, A.FZJ* ; Carius, R.FZJ* ; Meier, M.FZJ*

2015
American Inst. of Physics Melville, NY

Journal of applied physics 118(21), 215304 - (2015) [10.1063/1.4936616]

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Please use a persistent id in citations: http://hdl.handle.net/2128/17054 doi:10.1063/1.4936616

Abstract: The intrinsic microcrystalline absorber layer growth in thin-filmsilicon 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 celldevice 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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