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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

Topical Section: The solar cell

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 Voc (iVoc) by ~ 125 mV. The iVoc 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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1. Taguchi M, Yano A, Tohoda S, et al. (2013) 24.7% record efficiency HIT solar cell on thin silicon wafer. Proceedings of the 39th IEEE Photovoltaic Specialist Conference, Tampa, Florida, USA, pp. 96–99.

2. Masuko K, Shigematsu M, Hashiguchi T, et al. (2014) Achievement of more than 25% coversion efficiency with crystalline silicon heterojunction solar cell. IEEE J Photovoltaics 4: 1433–1435.    

3. Feldmann F, Bivour M, Reichel C, et al. (2014) Passivated rear contacts for high-efficiency n-type Si solar cells providing high interface passivation quality and excellent transport characteristics. Sol Energy Mater Sol Cells 120: 270–274.    

4. Heng JB, Fu J, Kong B, et al. (2015) >23% high-efficiency tunnel oxide junction bifacial solar cell with electroplated Cu gridlines. IEEE J Photovoltaics 5: 82–86.    

5. Lee WC, Hu CM (2001) Modeling CMOS tunneling currents through ultrathin gate oxide due to conduction-and valence-band electron and hole tunneling. IEEE Trans Electron Devices 48: 1366–1373.    

6. Sinton RA, Cuevas A, Stuckings M (1996) Quasi-steady-state photoconductance, a new method for solar cell material and device characterization. Proceedings of the 25th IEEE Photovoltaic Specialists Conference, Washington D.C., USA, pp. 457.

7. Kane DE, Swanson RM (1985) Measurement of the emitter saturation current by a contactless photoconductivity decay method (silicon solar cells). Proceedings of the 18th IEEE Photovoltaic Specialists Conference, Las Vegas, Nevada, USA, pp. 578–583.

8. Hermle M, Benick J, Rüdiger M, et al. (2011) N-type silicon solar cells with implanted emitter. Proceedings of the 26th European Photovoltaic Solar Energy Conference, Hamburg, Germany, pp. 875.

9. Tao Y, Rohatgi A (2014) High-efficiency large area ion-implanted n-type front junction Si Solar cells with screen-printed contacts and SiO2 passivated boron emitters. Proceedings of the 40th IEEE Photovoltaic Specialists Conference, Denver, Colorado, USA, pp. 3654–3658.

10. Yablonovitch E, Gmitter T, Swanson RM, et al. (1985) A 720 mV open circuit voltage SiOx:c-Si:SiOx double heterostructure solar cell. Appl Phys Lett 47: 1211–1213.    

11. Feldmann F, Simon M, Bivour M, et al. (2014) Efficient carrier-selective p- and n-contacts for Si solar cells. Sol Energy Mater Sol Cells 131: 100–104.    

12. Nemeth B, Young DL, Yuan H, et al. (2014) Low temperature Si/SiOx/pc-Si passivated contacts to n-type Si solar cells. Proceedings of the 40th IEEE Photovoltaic Specialist Conference, Denver, Colorado, USA, pp. 3488–3452.

13. Wolstenholme GR, Jorgensen N, Ashburn P, et al. (1987) An investigation of the thermal stability of the interfacial oxide in polycrystalline silicon emitter bipolar transistors by comparing device results with high-resolution electron microscopy observations. J Appl Phys 61: 225–233.    

14. Tao Y, Ok Y-W, Zimbardi F, et al. (2014) Fully ion-implanted and screen-printed 20.2% efficient front junction silicon cells on 239 cm2 N-type Cz substrate. IEEE J Photovoltaics 4: 58–63.

15. Hoex B, Schmidt J, Bock R, et al. (2007) Excellent passivation of highly doped p-type Si surfaces by the negative-charge-dielectric Al2O3. Appl Phys Lett 91: 112107.    

16. Renshaw J, Kang MH, Meemongkolkiat V, et al. (2009) 3D-modeling of a back point contact solar cell structure with a selective emitter. Proceedings of the 34th IEEE Photovoltaic Specialists Conference, Philadelphia, Pennsylvania, USA, pp. 375–379.

17. Altermatt PP (2011) Models for numerical device simulations of crystalline silicon solar cells–a review. J Comput Electron 10: 314–330.    

18. Bivour M, Reichel C, Hermle M, et al. (2012) Improving the a-Si:H(p) rear emitter contact of n-type silicon solar cells. Sol Energy Mater Sol Cells 106: 11–16.


Copyright Info: © 2016, Yuguo Tao, et al., licensee AIMS Press. This is an open access article distributed under the terms of the Creative Commons Attribution Licese (http://creativecommons.org/licenses/by/4.0)

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