Surface Passivation of Crystalline Silicon Solar Cells: A Review Armin G. Aberle Progress in Photovoltaics: Research and Application 8,473-487,2000. Outline Introduction Fundamental physics Surface passivation method Surface passivation of c-Si solar cells 2010/8/27 NCTU IEO GPL 2/5 Introduction Defects Extrinsic (Processing related) Intrinsic (Si related, unavoidable) Dangling bond Growth condition Dislocation 2010/8/27 NCTU IEO GPL 3/5 Surface type in Si solar cell Metalized Finger and bus bar Very high surface recombination Avoid recombination loss Non-metalized Illuminated region Well passivated and good blue response Avoid highly doped Back electrode high surface recombination Avoid recombination loss 2010/8/27 NCTU IEO GPL 4/5 Surface recombination Shockley-Read-Hall (SRH) theory Surface Recombination rate: Ec Et Ev Low recombination rate strategy 1. low surface state Nst 2. low carrier concentration ns, ps 2010/8/27 NCTU IEO GPL 5/5 Reduction of the surface states Growth/deposition of a dielectric film SiO2 Al2O3 d SiNx 4n Antireflective coating layer Dielectric layer(d) Si solar cell Chemical methods HF immersion Alcoholic solution 2010/8/27 NCTU IEO GPL 6/5 Field-effect passivated High-low junction p+-p n+-n Back surface field (BSF) Front surface field (FSF) p-n junction MIS Selective emitter HIT(a-Si) 2010/8/27 NCTU IEO GPL 7/5 Combined passivaction 2010/8/27 NCTU IEO GPL 8/5 Concept Al2O3 + + + + + + - e- h+ The fixed charge induced the negative charge on the surface, bending the band diagram. Al2O3 is suitable to p-type Si substrate. 2010/8/27 NCTU IEO GPL 9/5 PERL solar cells Passivated Emitter and Rear Locally Diffused Solar Cell (24.7%) 2010/8/27 NCTU IEO GPL 10/5 Band offset measurement The Si substrate can passivated by dielectric film and electric field effect method. The Al2O3 is suitable for p-type Si substrate passivation, and the SiNx is suitable for n-type Si substrate passivation. 2010/8/27 NCTU IEO GPL 11/5 Thanks for your attention!!