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Electron-Selective Epitaxial/Amorphous Germanium Stack Contact for Organic-Crystalline Silicon Hybrid Solar Cells

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journal contribution
posted on 22.08.2018, 00:00 by Bingbing Chen, Jianhui Chen, Kunpeng Ge, Linlin Yang, Yanjiao Shen, Wanbing Lu, Li Guan, Lizhi Chu, Qingxun Zhao, Yinglong Wang, Ying Xu, Yaohua Mai
Carrier transport properties can be improved through suppressing the charge carrier recombination and decreasing the contact resistance using the proper carrier-selective contact. In this work, an epitaxial/amorphous germanium (epi/a-Ge) stack thin film is introduced into the rear surface of organic–inorganic hybrid (OIH) solar cells as an efficient electron-selective contact. This novel electron-selective stack contact simultaneously contributes low recombinative and resistive losses through a three-material system composed of n-type silicon (n-Si), epitaxial silicon germanium (epi-SiGe), and amorphous germanium (a-Ge), which promotes the tailoring of band structures, the passivation of surface dangle bond defects, and the formation of Ohmic contact. The results show obvious improvement in the open-circuit voltage (Voc) (from 549.5 to 643.0 mV) and fill factor (FF) (from 70.5 to 75.4%), corresponding to the increase in the power conversion efficiency (PCE) of OIH solar cells (from 10.3 to 12.9%). This work indicates novel application of the carrier-selective stack contact to achieve high-performance OIH solar cells with a simple and low-temperature process.