Lithium Fluoride Based Electron Contacts for High Efficiency n‐Type Crystalline Silicon Solar Cells |
| |
Authors: | 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 Aïcha Hessler‐Wyser Andres Cuevas Ali Javey |
| |
Institution: | 1. Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, USA;2. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA;3. Research School of Engineering, The Australian National University (ANU), Canberra, ACT, Australia;4. école Polytechnique Fédérale de Lausanne (EPFL), Institute of Micro Engineering (IMT), Photovoltaics and Thin‐Film Electronic Laboratory (PVLab), Neuchatel, Switzerland |
| |
Abstract: | 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 LiFx/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. |
| |
Keywords: | contacts lithium fluoride photovoltaics silicon solar cells fermi levels |
|
|