Parasitic Absorption in Polycrystalline Si-layers for Carrier-selective Front Junctions

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• 作者：Sina Reiter^a ; ^{reiter@isfh.de" class="auth_mail" title="E-mail the corresponding author} ; Nico Koper^a ; Rolf Reineke-Koch^a ; Yevgeniya Larionova^a ; Mircea Turcu^a ; Jan Kr&uuml ; gener^b ; Dominic Tetzlaff^b ; Tobias Wietler^b ; Uwe Hö ; hne^c ; Jan-Dirk Kä ; hler^c ; Rolf Brendel^a ; ^d ; Robby Peibst^a ; ^b
• 关键词：Polycrystalline silicon ; optical properties ; front junction ; ray tracing simulations
• 刊名：Energy Procedia
• 出版年：2016
• 出版时间：August 2016
• 年：2016
• 卷：92
• 期：Complete
• 页码：199-204
• 全文大小：864 K

文摘

We investigate the optical properties of n- and p-type polycrystalline silicon (poly-Si) layers. We determine the optical constants n and k of the complex refractive index of polycrystalline silicon by using variable-angle spectroscopic ellipsometry. Moreover, we investigate the effect of different doping levels in the poly-Si on free carrier absorption (FCA). Thereby, we demonstrate that the FCA in poly-Si can be described by a model developed for crystalline silicon (c-Si) at a first approximation. The optical properties of hydrogenated amorphous silicon layers (a-Si:H) are also investigated as a reference. With ray tracing simulations the absorption losses of poly-Si and of the a-Si:H layers are quantified with respect to the film thickness. Based on this approach we find that the short-circuit current density losses due to parasitic absorption of poly-Si layers are significantly lower when compared to a-Si:H layers of the same thickness. For example the short-circuit current density loss due to a 20 nm thick p-type poly-Si layer is around 1.1 mA/cm², whereas a 20 nm thick p-type a-Si:H layer leads to a loss of around 3.5 mA/cm².