Back Surface Recombination Effect on the Ultra-Thin CIGS Solar Cells by SCAPS

Year 2014, Volume: 4 Issue: 4, 958 - 964, 01.12.2014

Naima Touafek R. Mahamadi

Abstract

the impact of the back surface recombination velocity (SR) and the presence of the Electron Back Reflector (EBR) on the performance of CIGS solar cell when varying the absorber thickness from 0.3 to 2 µm is illustrated by the diverse results obtained by simulation using SCAPS. Thinner devices are more affected than thick ones by the variations of the EBR and SR. The gain in efficiency due to the reducing SR is increased as the absorber thickness is reduced. The results revealed that for thin absorbent layer less than 1µm the efficiency of the CIGS cell can be increased by 1-3% depending on the thickness if the SR is reduced to lower than 103 cm/s. This leads to enhance the Voc and efficiency which become comparable to those obtained for standard devices (2µm). For high SR the electron back reflector plays much more significant role and becomes beneficial. However the high band gap of EBR does not necessary result in high performance where the results show that 0.2 eV of EBR height is sufficient to enhance the performance. Independently to the absorber thickness the efficiency increased sharply, especially for thinner device, when an EBR with thickness around 5% corresponding of the total CIGS thickness was added at the back surface. The gain in efficiency increases as the thickness of the layers is reduced and reaches the same levels as the standard devices. As the thickness of EBR is increased, the reduction of Jsc is fairly recovered by the augmentation of Voc which leads to a slight reduction in efficiency especially for thinner device.

Keywords

Cu(In, Ga)Se2; Solar cell; Back Surface Velocity; EBR; SCAPS-1D.

References

• A. Luque and S. Hegedus, Handbook of Photovoltaic Energy Conversion and Engineering: John Wiley & Sons LTD, Chichester, West Sussex, England, 2003.
• R. Noufi and K. Zwiebel, “High-Efficiency CdTe and CIGS challenges”, The 4th World Conference Photovoltaic Energy Conversion. Hawaii, pp. 317-320, 7-12 May 2006. Cells: Highlights and
• S.S. Viswanathan, C. IK-Ho, L. Chi-Woo. “Progress in electrodeposited absorber layer for CuIn(1-x)GaxSe2 (CIGS) solar cells”. Solar Energy. Vol. 85, pp. 2666- 2678,2011.
• J. krc et al.”Optical and electrical modeling of Cu(In,Ga)Se2 solar cells”. Optical and Quantum Electronics. vol. 38, pp. 1115-1123, 2006.
• A.Yamada et al.”Built-in potential and open circuit voltage of heterojunction CuIn1-xGaxSe2 solar cells”. Proc. Mater. Res. Soc. Symp. USA, vol. 865, pp. F5.19.1-F5.19.6, 2005.
• P. Chelvanathan, MI. Hossain, and N. Amin. “Performance analysis of copper-indium-gallium (CIGS) solar cells with various buffer layers by SCAPS”. Curr. Appl. Phys. vol. 10, No, 3, pp.387-391, 2010.
• O. Lundberg, M. Bodegard, J. Malmstrom, and M. Stolt. “Influence of the Cu(In,Ga)Se2 thickness and Ga grading on solar cell performance”. Prog. Photovoltaics Res. Appl. vol.11, pp. 77–88 2003.
• Z. Jehl et al. “Thinning of CIGS solar cells: part II: cell characterizations”. Thin Solid Films. Vol. 519, pp. 7212–7215, 2011.
• B. Vermang, V. Fjallstrom, J. pettersson, P. Salomé, and M. Edoff. “Development of rear surface passivated Cu(In,Ga)Se2 thin film solar cells with nano-sized local rear point contacts”. Solar Energy Materials and Solar cells. vol. 117, pp. 505-511, 2013.
• W.W. Hsu et al. “surface passivation of Cu(In,Ga)Se2 using atomic layer deposited Al2O3”. Applied Physics Letters. Vol. 100, pp. 1-4, 2012.
• J. Petterson, C. Platzer-bjorkman, U. Zimmermann, and M. Edoff. “Baseline model of graded-absorber Cu(In,Ga)Se2 solar cells applied to cells with Zn1- xMgxO buffer layers”. Thin Solid Films. vol. 519, pp.7476-7480, 2011.
• R. W. Miles, G. Zoppi, and I. Forbes. “Inorganic photovoltaic cells”. Mater today. vol. 10, No. 11, pp. 20-27, 2007.
• J.M. Burgelman. “Numerical modeling of intra-band tunneling for heterojunction solar cells in SCAPS”. Thin Solid Films. Vol. 515, pp. 6276-6279, 2007.
• H. Movla, D. Salami, S.V. Sadreddini. “Simulation analysis of the effect of defect density on the performance of p-i-n InGaN solar cell”. Applied Physics A. vol. 109, pp. 497-502, 2012.
• M. Burgelman, P. Nollet, S. Degrave. “Modeling polycrystalline semiconductor solar cells”. Thin Solid Films. Vol.361-362, pp. 527-532, 2000.
• S. J. Fonash. Solar Cell Device Physics, 2nd ed., USA, Academic Press (Elsevier), 2010.
• Metzger, K. Wyatt. “The potential and device physics of interdigitated thin-film solar cells”. Journal of Applied Physics. Vol. 103, No.9, pp.094515, 2008.
• A. O. Pudov. “Impact of secondary barriers on CuIn1- xGaxSe2 solar-cell operation” [Doctoral thesis].Colorado state University, 2005.
• Z. Jehl et al. “thinning of CIGS solar cells: Part II: cell characterizations”. Thin solid films. vol. 519, pp. 7212- 7215, 2011.
• K. Orgassa. “Coherent Optical Analysis of the ZnO/CdS/Cu(In,Ga)Se2 [Doctoral thesis]. University of Stuttgart, 2004.
• Thin Film Solar Cell”
• S.R. Seyrling, “Advanced Concepts for Cu(In,Ga)Se2 Thin Film Solar Cells” [Doctoral thesis]. ETH ZURICH, 2011.