Fourteen percent efficiency ultrathin silicon solar cells with improved infrared light management enabled by hole‐selective transition metal oxide full‐area rear passivating contacts

• Published in: Progress in photovoltaics 2022-08, Vol.30 (8), p.823-834
• Main Authors: Nasser, Hisham, Borra, Mona Zolfaghari, Çiftpınar, Emine Hande, Eldeeb, Basil, Turan, Raşit
• Format: Article
• Language: English
• Subjects: asymmetric heterocontacts; dopant‐free; Electromagnetic absorption; hole‐selective contacts; metal oxide; Metal oxides; passivating contacts; Photovoltaic cells; Room temperature; Silicon; Silver; Solar cells; Thin films; Transition metal oxides; ultrathin c‐Si; Work functions
• ISSN: 1062-7995; 1099-159X
• DOI: 10.1002/pip.3510

The present study investigates the application of hole‐selective transition metal oxide (TMO) layers (MoOx, V2Ox, and WOx) with silver (Ag) as full‐area rear contact to 22.5 μm‐thick low‐quality Cz p‐type c‐Si solar cells. Thin films of metal oxides are deposited directly on p‐type c‐Si by thermal evaporation at room temperature. The large work function of these TMOs creates strong accumulation at the interface with p‐type c‐Si, which allows only holes to transport and simultaneously suppress the interfacial recombination current density (J0) and contact resistivity (ρc). The current generation and losses of 22.5 μm‐thick solar cells with different hole‐selective TMO/Ag at the rear are simulated. The presence of TMO/Ag at the rear is found to significantly reduce parasitic light absorption at longer wavelengths which becomes more pronounced for ultrathin wafers, providing significant advantages over conventional Al contact. The best device performance was attained by the MoOx/p‐type c‐Si solar cells, demonstrating a considerably high efficiency (η) of 14% with Voc of 555 mV, FF of 76.0%, and Jsc of 33.2 mA/cm2. Furthermore, the present work is the first to employ MoOx, V2Ox, and WOx as rear contact in ultrathin p‐type c‐Si solar cells. A total of 22.5 μm‐thick c‐Si solar cells based on low‐quality Cz p‐type c‐Si wafers with efficiency of 14% have been realized from MoOx/Ag full‐area hole‐selective rear contact. This efficiency is achieved because the Si rear side is passivated by the TMO. Light absorption in thin c‐Si is greatly enhanced without utilizing advanced light trapping interface.