PVMD Arno Smets Delft University of Technology Learning objectives - PowerPoint PPT Presentation

Silicon phases and alloys PVMD Arno Smets Delft University of Technology

Learning objectives • What are the different phases of silicon • What other silicon alloys are used in thin film solar cells • How do these alloys improve solar cell performance

Silicon phases Decreasing crystalline volume fraction nanocrystalline amorphous Stationary columnar Several 100 nm growth Incubation layer 30-50nm ~ Substrate

Silicon phases Crystallinity Volume fraction of the crystalline phase to the total silicon volume

Nanocrystalline film Matsui et al. Jpn. J. Appl. Phys. 42, L901 (2003)

Silicon alloys VlllA 2 1 He H lllA lVA VA VlA VllA 4.003 5 6 7 8 9 10 a-Si:H B C N O F Ne 10.811 12.011 14.007 15.999 18.998 20.183 nc-Si:H 13 14 15 16 17 18 Al Si P S Cl Ar lB llB a-Si x Ge 1-x :H 26.982 28.086 30.974 32.064 35.453 39.948 29 30 31 32 33 34 35 36 nc-Si x Ge 1-x :H Cu Zn Ga Ge As Se Br Kr 63.54 65.37 69.72 72.59 74.922 78.96 79.909 83.80 a-Si x C 1-x :H 47 48 49 50 51 52 53 34 Ag Cd In Sn Sb Te I Xe 107.870 112.40 114 82 118 69 121.75 127 60 126 904 131 30 nc-Si x O 1-x :H 97 80 81 82 83 84 85 86 Au Hg Tl Pb Bi Po At Rn 196.967 200.59 204.37 207.19 208.980 (210) (210) (222)

Silicon alloy ranges absorption no absorption 2.00 1.75 alloy Band gap (eV) 1.50 P( λ ) (W m -2 nm -1 ) a-Si:H 1.6-1.8 1.25 nc-Si:H 1.1-1.3 1.00 AM 1.5 a-SiGe:H 1.4-1.6 0.75 a-SiC:H >1.9 0.50 nc-SiO:H >2.0 0.25 0.00 500 1000 1500 2000 2500 0 Wavelength (nm)

Micromorph tandem cell a-Si:H nc-Si:H P I N P I N glass _ _ TCO CB a-Si:H p-i-n junction E Fermi + + nc-Si:H p-i-n junction VB Metal back contact 150 - 300 nm 1000 - 2000 nm

Triple junction cell glass TCO 1 a-Si:H p-i-n junction 2 a-SiGe:H p-i-n junction 3 nc-Si:H p-i-n junction Metal back contact 12 1 123

Crystallinity Volume fraction of the crystalline phase to the total silicon volume