Lithium Fluoride Based Electron Contacts for High Efficiency n-Type Crystalline Silicon Solar Cells

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• 作者：James Bullock ; Peiting Zheng ; Quentin Jeangros ; Mahmut Tosun ; Mark Hettick ; Carolin M. Sutter-Fella ; Yimao Wan ; Thomas Allen ; Di Yan ; Daniel Macdonald ; Stefaan De Wolf ; Aï ; cha Hessler-Wyser ; Andres Cuevas and Ali Javey
• 刊名：Advanced Energy Materials
• 出版年：2016
• 出版时间：July 20, 2016
• 年：2016
• 卷：6
• 期：14
• 全文大小：1243K
• ISSN：1614-6840

文摘

Low-resistance contact to lightly doped n-type crystalline silicon (c-Si) has long been recognized as technologically challenging due to the pervasive Fermi-level pinning effect. This has hindered the development of certain devices such as n-type c-Si solar cells made with partial rear contacts (PRC) directly to the lowly doped c-Si wafer. Here, a simple and robust process is demonstrated for achieving mΩ cm² scale contact resistivities on lightly doped n-type c-Si via a lithium fluoride/aluminum contact. The realization of this low-resistance contact enables the fabrication of a first-of-its-kind high-efficiency n-type PRC solar cell. The electron contact of this cell is made to less than 1% of the rear surface area, reducing the impact of contact recombination and optical losses, permitting a power conversion efficiency of greater than 20% in the initial proof-of-concept stage. The implementation of the LiF_x/Al contact mitigates the need for the costly high-temperature phosphorus diffusion, typically implemented in such a cell design to nullify the issue of Fermi level pinning at the electron contact. The timing of this demonstration is significant, given the ongoing transition from p-type to n-type c-Si solar cell architectures, together with the increased adoption of advanced PRC device structures within the c-Si photovoltaic industry.