One‐Step Formation of Low Work‐Function, Transparent and Conductive MgFxOy Electron Extraction for Silicon Solar Cells

• Published in: Advanced science 2022-08, Vol.9 (23), p.n/a
• Main Authors: Li, Junjun, Guo, Cong, Bai, Yu, Liu, Wenzhu, Chen, Yang, He, Jialong, Li, Dongdong, Yang, Xinbo, Qiu, Qingqing, Chen, Tao, Yu, Junsheng, Huang, Yuelong, Yu, Jian
• Format: Article
• Language: English
• Subjects: Annealing; dopant‐free solar cells; Efficiency; electron selective contact; Etching; Fluorides; Glass substrates; high transmittance; LiFx/MgFxOy stack; low work function; Magnesium; Photovoltaic cells; Silicon; Spectrum analysis; Zinc oxides
• ISSN: 2198-3844; 2198-3844
• DOI: 10.1002/advs.202202400

The development of high‐performance dopant‐free silicon solar cells is severely bottlenecked by opaque electron selective contact. In this paper, high transmittance (80.5% on glass) and low work function (2.92 eV) lithium fluoride (LiFx)/MgFxOy electron contact stack by tailoring the composition of MgFxOy hybrid film is reported. This hybrid structure exhibits a high conductivity (2978.4 S cm−1) and a low contact resistivity (2.0 mΩ cm2). The element profile of LiFx/MgFxOy contact is measured and the reaction kinetics is analyzed. As a proof‐of‐concept, this electron selective contact is applied for dopant‐free silicon solar cells. An impressive efficiency of 21.3% is achieved on dopant‐free monofacial solar cell with molybdenum oxide (MoOx)/zinc‐doped indium oxide (IZO) hole contact. An efficiency bifaciality of 71% is obtained for dopant‐free bifacial solar cell with full‐area LiFx/MgFxOy/ITO (tin‐doped indium oxide) transparent electron contact. It is the highest efficiency bifaciality so far for dopant‐free bifacial solar cells to the best knowledge. Both cell configurations with LiFx/MgFxOy contacts show excellent environment stability. The cell efficiency maintains more than 95% of its initial value after keeping in air for 1500 h. This work provides a new idea to achieve transparent electron contact, showing a great potential for high‐efficiency and low‐cost optoelectronic devices. A low work function, transparent, and conductive lithium fluoride (LiFx)/MgFxOy electron extraction stack is reported. By applying the electron contact, a dopant‐free monofacial silicon solar cell with an impressive efficiency of 21.3% is achieved. And an efficiency bifaciality of 71% is reported for bifacial device. This work provides a new idea to achieve transparent electron selective contacts.