1 Tandem and thinfilm solar cells LECTURE 22

2 Efficiency comparison: materials and modules

3 Thin sc-Si solar cells K. J. Weber et al. , IEEE Photovoltaic Specialists

4 Sec. 7. 6. 2 Multijunction cells: concept and practice http: //www. emcore. com/assets/photovoltaics/Emcore_Manuscript_Fatemi_3

5 Matching the materials J. M. Román, “State-of-theart of III-V Solar Cell Fabrication Technologies,

9 More CIGS properties Electron minority carrier diffusion lengths: 0. 5 – 2. 5

10 10 Even more properties of Cu. In 1 -x. Gax. Se 2 •

11 Preparation of Cu. In 1 -x. Gax. Se 2 www. tf. uni-kiel. de/.

12 12 Sec. 7. 6. 1 CIGS cells: a lower cost alternative (? )

13 13 Heterojunction advantages and problems E EC Wide bandgap window, but what happens

14 A proposed band diagram www. tf. uni-kiel. de/. . . en/. . .

15 Real heterostructures What are the effects on the electrical properties of some previously

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1 Tandem and thin-film solar cells LECTURE 22 • Si sliver cells • tandem junction solar cells • CIGS as a promising solar absorber • CIGS solar cells • heterojunction basics • surface phenomena

2 Efficiency comparison: materials and modules

3 Thin sc-Si solar cells K. J. Weber et al. , IEEE Photovoltaic Specialists Conf. , 991 -994, 2005. 10 X reduction in Si use claimed

4 Sec. 7. 6. 2 Multijunction cells: concept and practice http: //www. emcore. com/assets/photovoltaics/Emcore_Manuscript_Fatemi_3 P-B 5 -03_WCPEC-3. pdf

5 Matching the materials J. M. Román, “State-of-theart of III-V Solar Cell Fabrication Technologies, Device Designs and Applications, ” Advanced Photovoltaic Cell Design, 2004. http: //photochemistry. epfl. ch/EDEY/NREL. p df

6 The world-record holder

7 Sec. 7. 6. 2 Cell mismatch

8 Sec. 7. 2 CIGS properties

9 More CIGS properties Electron minority carrier diffusion lengths: 0. 5 – 2. 5 micron Photovoltaic Materials, Richard Bube

10 10 Even more properties of Cu. In 1 -x. Gax. Se 2 • Chalcopyrite structure, tetragonal bonding • Vacancy doping* • Direct bandgap • Eg(x) 1. 04 - 1. 7 e. V • High absorption coefficient • Can be printed onto glass and metal • Needs heteroface cell structure • Google has invested $$$$$ in it. *

11 Preparation of Cu. In 1 -x. Gax. Se 2 www. tf. uni-kiel. de/. . . en/. . . /gerngross_reverey_paper_ws_08_1. pdf

12 12 Sec. 7. 6. 1 CIGS cells: a lower cost alternative (? ) Noufi, Rommel; Ken Zweibel. HIGH-EFFICIENCY CDTE AND CIGS THIN-FILM SOLAR CELLS: HIGHLIGHTS AND CHALLENGES. National Renewable Energy Laboratory.

13 13 Heterojunction advantages and problems E EC Wide bandgap window, but what happens at the interfaces? EV x And why is Cd. S needed?

14 A proposed band diagram www. tf. uni-kiel. de/. . . en/. . . /gerngross_reverey_paper_ws_08_1. pdf

15 Real heterostructures What are the effects on the electrical properties of some previously unconsidered real surface effects? • surface reconstruction • dipole formation • interruption of the periodicity of the semiconductor • surface states