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

PVMD

Delft University of Technology

Silicon phases and alloys

Arno Smets

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

Incubation layer Stationary columnar growth Substrate Several 100 nm 30-50nm

~ nanocrystalline amorphous

Decreasing crystalline volume fraction

Silicon phases

Crystallinity

Volume fraction of the crystalline phase to the total silicon volume

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

Nanocrystalline film

Rn Xe Kr Ar Ne He At I Br Cl F Po Te Se S O Bi Sb As P N Pb Sn Ge Si C Tl In Ga Al B Hg Cd Zn Au Ag Cu

VlllA VllA VA lllA llB lB

2 10 18 36 34 86 9 17 35 53 85 8 16 34 52 84 7 15 33 51 83 6 14 32 50 82 5 13 31 49 81 30 48

80

29 47 97 4.003 20.183 39.948 83.80 131 30 (222) 35.453 79.909 126 904 (210) 18.998 32.064 78.96 127 60 (210) 15.999 30.974 74.922 121.75 208.980 14.007 28.086 72.59 118 69 207.19 12.011 26.982 69.72 204.37 10.811 65.37 112.40 200.59 63.54 107.870 196.967 114 82

H

1

Silicon alloys

a-Si:H nc-Si:H a-SixGe1-x:H nc-SixGe1-x:H a-SixC1-x:H nc-SixO1-x:H

lVA VlA

2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0.00

P(λ) (W m-2 nm-1)

500 1000 1500 2000 2500

Wavelength (nm)

AM 1.5 absorption no absorption

Silicon alloy ranges

alloy Band gap (eV) a-Si:H 1.6-1.8 nc-Si:H 1.1-1.3 a-SiGe:H 1.4-1.6 a-SiC:H >1.9 nc-SiO:H >2.0

Micromorph tandem cell

a-Si:H p-i-n junction nc-Si:H p-i-n junction Metal back contact glass TCO EFermi CB VB 1000 - 2000 nm 150 - 300 nm P I N P I N a-Si:H nc-Si:H

+ _ + _

Triple junction cell

a-Si:H p-i-n junction a-SiGe:H p-i-n junction nc-Si:H p-i-n junction Metal back contact TCO glass

1 2 3 1 12 123

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