Papers by Otwin Breitenstein
Solar Energy Materials and Solar Cells, 2015
Solar Energy Materials and Solar Cells, 2015
physica status solidi (c), 2015
Springer Series in Advanced Microelectronics, 2003
Springer Series in Advanced Microelectronics, 2003
Springer Series in Advanced Microelectronics, 2010
2014 IEEE 40th Photovoltaic Specialist Conference (PVSC), 2014
The ongoing trend to decrease the wafer thickness in the fabrication of silicon solar cells incre... more The ongoing trend to decrease the wafer thickness in the fabrication of silicon solar cells increases the number of possible cracks. Therefore, an in-depth understanding of the influence of cracks on solar cells is necessary. In this work, we investigate silicon solar cells with cracks by employing three camera-based spatially-resolved techniques and use the data to quantitatively calculate local-current voltage parameters. Cracks mainly influence the recombination current density of a silicon solar cell. This fact is clearly shown by drastically increased recombination in the space charge region. This recombination reduces parameters like fill factor, open circuit voltage and the cell efficiency. The comparison of the solar cell data before and after the formation of cracks shows a 0.2 % absolute efficiency loss in the global current-voltage parameters and up to 1 % absolute efficiency loss in the local current-voltage analysis at the crack positions.
Solid State Phenomena, 2009
This work introduces two different approaches to explain the growth of silicon carbide (SiC) fila... more This work introduces two different approaches to explain the growth of silicon carbide (SiC) filaments, found in the bulk material and in grain boundaries of solar cells made from multicrystalline (mc) silicon. These filaments are responsible for ohmic shunts. The first model proposes that the SiC filaments grow at the solid-liquid interface of the mc-Si ingot, whereas the second model proposes a growth due to solid state diffusion of carbon atoms in the solid fraction of the ingot during the block-casting process. The melt interface model can explain quantitatively the observed morphologies, diameters and mean distances of SiC filaments. The modeling of the temperature-and time-dependent carbon diffusion to a grain boundary in the cooling ingot shows that solid state diffusion based on literature data is not sufficient to transport the required amount of approximately 3.4 × 10 17 carbon atoms per cm 2 to form typical SiC filaments found in grain boundaries of mc-Si for solar cells. However, possible mechanisms are discussed to explain an enhanced diffusion of carbon to the grain boundaries.
Solid State Phenomena, 1991
Solid State Phenomena, 2009
The current-voltage (I-V) characteristics of most industrial silicon solar cells deviate rather s... more The current-voltage (I-V) characteristics of most industrial silicon solar cells deviate rather strongly from the exponential behavior expected from textbook knowledge. Thus, the recombination current may be orders of magnitude larger than expected for the given material quality and often shows an ideality factor larger than 2 in a wide bias-range, which cannot be explained by classical theory either. Sometimes, the cells contain ohmic shunts although the cell's edges have been perfectly insolated. Even in the absence of such shunts, the characteristics are linear or super-linear under reverse bias, while a saturation would be classically expected. Especially in multicrystalline cells the breakdown does not tend to occur at -50 V reverse bias, as expected, but already at about -15 V or even below. These deviations are typically caused by extended defects in the cells. This paper reviews the present knowledge of the origin of such nonideal I-V characteristics of silicon solar cells and introduces new results on recombination involving coupled defect levels. Solid State Phenomena Vols. 156-158 (2010) pp 1-10 online at http://www.scientific.net
Opto-Electronics Review, 2013
Microelectronic Engineering, 2001
Microelectronic Engineering, 1990
Materials Science in Semiconductor Processing, 2001
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Papers by Otwin Breitenstein