Hydrogenated amorphous silicon based solar cells: optimization formalism and numerical algorithm
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1153-A07-05
Hydrogenated amorphous silicon based solar cells: optimization formalism and numerical algorithm A.I. Shkrebtii1,*, Yu.V.Kryuchenko1, 2, A.V.Sachenko2, I.O.Sokolovskyi1, 2, and F.Gaspari1 1 2
University of Ontario Institute of Technology, Oshawa, ON, L1H 7L7, Canada V. Lashkarev Institute of Semiconductor Physics NAS, Kiev, 03028, Ukraine
ABSTRACT Thin film hydrogenated amorphous silicon (a-Si:H) is widely used in photovoltaics. In order to get the best possible performance of the a-Si:H solar cells it is important to optimize the amorphous film and solar cells in terms their parameters such as mobility gap, p-, i- and n-layer doping levels, electron and hole lifetime and their mobilities, resistance of p-, i- and n-layers, contact grid geometry and parameters of the transparent conducting and antireflecting layers, and others. To maximize thin a-Si:H film based solar cell performance we have developed a general numerical formalism of photoconversion, which takes into account all the above parameters for the optimization. Application of the formalism is demonstrated for typical a-Si:H based solar cells before Staebler-Wronski (SW) light soaking effect. This general formalism is not limited to a-Si:H based systems only, and it can be applied to other types of solar cells as well.
INTRODUCTION Amorphous silicon based solar cells are very promising because of low production cost, possibility of covering large uneven areas, and sufficiently high efficiency 1. In order to get the best performance of the a-Si:H solar cells it is important first to produce a high quality and stable amorphous film and p-i-n junction. Secondly, optimization of the solar cells is a crucial part of the solar cell design. A few approaches to optimize performance of various types of solar cells are available, both analytical and numerical 2. Analytical models have the advantage of being physically intuitive and of providing the possibility of quick estimation of photo-conversion efficiency. Previously, we have developed an analytical three-dimensional photoconversion model and applied it to optimize the amorphous Si based solar cell 3. However, to further advance the solar cell optimization, more detailed approaches, numerical rather than analytical, are required. A few problems have to be overcome to create efficient a-Si:H solar cells. The main problem related with a-Si:H based devices is the material stability due to the formation of metastable defects in a-Si:H that reduces the performance of these devices. Staebler and Wronski 4 found that defects can be created by illuminating a-Si:H, which decreases dark and photo conductivity. Several models have been proposed to explain the mechanism of the Staebler-Wronski (SW) effect, but no consensus has yet been reached. Microscopic mechanisms of hydrogen rebonding and diffusion are important to understand this detrimental effect. To access such processes microscopically, we theoretically investigated hydrogen behavior in
a-Si:H using extensive first-principles finite temperature m
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