Tunnel oxide passivated rear contact for large area <em>n</em>-type front junction silicon solar cells providing excellent carrier selectivity

Yuguo Tao; Vijaykumar Upadhyaya; Keenan Jones; Ajeet Rohatgi; Yuguo Tao; Vijaykumar Upadhyaya; Keenan Jones; Ajeet Rohatgi

doi:10.3934/matersci.2016.1.180

AIMS Materials Science

2016, Volume 3, Issue 1: 180-189. doi: 10.3934/matersci.2016.1.180

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Tunnel oxide passivated rear contact for large area n-type front junction silicon solar cells providing excellent carrier selectivity

1.
Georgia Institute of Technology, 777 Atlantic Drive, Atlanta, GA 30332-0250, USA
2.
Suniva Inc., 5765 Peachtree Industrial Blvd., Norcross, GA 30092, USA

Received: 11 December 2015 Accepted: 24 January 2016 Published: 26 January 2016

Carrier-selective contact with low minority carrier recombination and efficient majority carrier transport is mandatory to eliminate metal-induced recombination for higher energy conversion efficiency for silicon (Si) solar cells. In the present study, the carrier-selective contact consists of an ultra-thin tunnel oxide and a phosphorus-doped polycrystalline Si (poly-Si) thin film formed by plasma enhanced chemical vapor deposition (PECVD) and subsequent thermal crystallization. It is shown that the poly-Si film properties (doping level, crystallization and dopant activation anneal temperature) are crucial for achieving excellent contact passivation quality. It is also demonstrated quantitatively that the tunnel oxide plays a critical role in this tunnel oxide passivated contact (TOPCON) scheme to realize desired carrier selectivity. Presence of tunnel oxide increases the implied V_oc (iV_oc) by ~ 125 mV. The iV_oc value as high as 728 mV is achieved on symmetric structure with TOPCON on both sides. Large area (239 cm²) n-type Czochralski (Cz) Si solar cells are fabricated with homogeneous implanted boron emitter and screen-printed contact on the front and TOPCON on the back, achieving 21.2% cell efficiency. Detailed analysis shows that the performance of these cells is mainly limited by boron emitter recombination on the front side.
Citation: Yuguo Tao, Vijaykumar Upadhyaya, Keenan Jones, Ajeet Rohatgi. Tunnel oxide passivated rear contact for large area n-type front junction silicon solar cells providing excellent carrier selectivity[J]. AIMS Materials Science, 2016, 3(1): 180-189. doi: 10.3934/matersci.2016.1.180

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Abstract

Carrier-selective contact with low minority carrier recombination and efficient majority carrier transport is mandatory to eliminate metal-induced recombination for higher energy conversion efficiency for silicon (Si) solar cells. In the present study, the carrier-selective contact consists of an ultra-thin tunnel oxide and a phosphorus-doped polycrystalline Si (poly-Si) thin film formed by plasma enhanced chemical vapor deposition (PECVD) and subsequent thermal crystallization. It is shown that the poly-Si film properties (doping level, crystallization and dopant activation anneal temperature) are crucial for achieving excellent contact passivation quality. It is also demonstrated quantitatively that the tunnel oxide plays a critical role in this tunnel oxide passivated contact (TOPCON) scheme to realize desired carrier selectivity. Presence of tunnel oxide increases the implied V_oc (iV_oc) by ~ 125 mV. The iV_oc value as high as 728 mV is achieved on symmetric structure with TOPCON on both sides. Large area (239 cm²) n-type Czochralski (Cz) Si solar cells are fabricated with homogeneous implanted boron emitter and screen-printed contact on the front and TOPCON on the back, achieving 21.2% cell efficiency. Detailed analysis shows that the performance of these cells is mainly limited by boron emitter recombination on the front side.

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