Large area tunnel oxide passivated rear contact n-type Si solar cells with 21.2% efficiency

• Published in: Progress in photovoltaics Vol. 24; no. 6; pp. 830 - 835
• Main Authors: Tao, Yuguo, Upadhyaya, Vijaykumar, Chen, Chia-Wei, Payne, Adam, Chang, Elizabeth Lori, Upadhyaya, Ajay, Rohatgi, Ajeet
• Format: Journal Article
• Language: English
• Published: Bognor Regis Blackwell Publishing Ltd 01.06.2016; Wiley Subscription Services, Inc
• Subjects: Contact; Current density; large area; n-type Cz wafer; Oxides; passivated contact; Passivation; Photovoltaic cells; room temperature; screen-printed; Silicon; Solar cells; tunnel oxide; Tunnels (transportation)
• ISSN: 1062-7995; 1099-159X
• DOI: 10.1002/pip.2739

This paper reports on the implementation of carrier‐selective tunnel oxide passivated rear contact for high‐efficiency screen‐printed large area n‐type front junction crystalline Si solar cells. It is shown that the tunnel oxide grown in nitric acid at room temperature (25°C) and capped with n+ polysilicon layer provides excellent rear contact passivation with implied open‐circuit voltage iVoc of 714 mV and saturation current density J0b′ of 10.3 fA/cm2 for the back surface field region. The durability of this passivation scheme is also investigated for a back‐end high temperature process. In combination with an ion‐implanted Al2O3‐passivated boron emitter and screen‐printed front metal grids, this passivated rear contact enabled 21.2% efficient front junction Si solar cells on 239 cm2 commercial grade n‐type Czochralski wafers. Copyright © 2016 John Wiley & Sons, Ltd. It was found that the tunnel oxide grown in nitric acid at room temperature (25°C) and capped with n+ polysilicon layer provided excellent rear contact passivation with implied open‐circuit voltage iVoc of 714 mV and saturation current density J0b′ of 10.3 fA/cm2 for the back surface field region. In combination with an ion‐implanted Al2O3‐passivated boron emitter and screen‐printed front metal grids, this tunnel oxide passivated rear contact enabled 21.2% efficient front junction Si solar cells on 239 cm2 commercial grade n‐type Czochralski wafers.