High-Efficiency Large-Area Rear Passivated Silicon Solar Cells With Local Al-BSF and Screen-Printed Contacts

This paper describes the cell design and technology on large-area (239 cm2) commercial grade Czochralski Si wafers using industrially feasible oxide/nitride rear passivation and screen-printed local back contacts. A combination of optimized front and back dielectrics, rear surface finish, oxide thickness, fixed oxide charge, and interface quality provided effective surface passivation without parasitic shunting. Increasing the rear oxide thickness from 40 to 90 Å in conjunction with reducing the surface roughness from 1.3 to 0.2 μm increased the Voc from 640 mV to 656 mV. Compared with 18.6% full aluminum back surface field (Al-BSF) reference cell, local back-surface field (LBSF) improved the back surface reflectance (BSR) from 65% to 93% and lowered the back surface recombination velocity (BSRV) from 310 to 130 cm/s. Two-dimensional computer simulations were performed to optimize the size, shape, and spacing of LBSF regions to obtain good fill factor (FF). Model calculations show that 20% efficiency cells can be achieved with further optimization of local Al-BSF cell structure and improved screen-printed contacts.

[1]  W. Warta,et al.  Field-effect passivation of the SiO2Si interface , 1999 .

[2]  Paul A. Basore,et al.  Numerical modeling of textured silicon solar cells using PC-1D , 1990 .

[3]  Takehiko Sato,et al.  Large-size multi-crystalline silicon solar cells with honeycomb textured surface and point-contacted rear toward industrial production , 2011 .

[4]  M. Green,et al.  22.8% efficient silicon solar cell , 1989 .

[5]  A. Rohatgi.  Developing novel low-cost, high-throughput processing techniques for 20%-efficient monocrystalline silicon solar cells , 2010 .

[6]  A. Rohatgi,et al.  The impact of cell design on light induced degradation in p-type silicon solar cells , 2011, 2011 37th IEEE Photovoltaic Specialists Conference.

[7]  K. Bothe,et al.  19.4%‐efficient large‐area fully screen‐printed silicon solar cells , 2011 .

[8]  K. A. Münzer,et al.  Advanced Rear Side Technology for Industrial High Efficiency Solar Cells , 2010 .

[9]  A. Rohatgi,et al.  Fabrication of 20 % efficient cells using spin-on based simultaneous diffusion and dielectric anneal , 2009, 2009 34th IEEE Photovoltaic Specialists Conference (PVSC).

[10]  Rudolf Hezel,et al.  Experimental evidence of parasitic shunting in silicon nitride rear surface passivated solar cells , 2002 .

[11]  A. Carr,et al.  19% efficient n-type Si solar cells made in pilot production , 2010 .

[12]  R. Sinton,et al.  Contactless determination of current–voltage characteristics and minority‐carrier lifetimes in semiconductors from quasi‐steady‐state photoconductance data , 1996 .

[13]  A. Rohatgi,et al.  Road to cost-effective crystalline silicon photovoltaics , 2003, 3rd World Conference onPhotovoltaic Energy Conversion, 2003. Proceedings of.