### 8.3.3 Summary to: 8.3 Making Thin Film Solar Cells

| Thin film solar cells need to meet some key requirements: |  |
CIGS | Multi junction
|  | Process-compatible and cheap substrate Þ large area deposition. Suitable direct band gap Þ high absorption coefficients f Insensitivity to "defects" Technology for junction and good ohmic contacts. |
| Major contenders in (or close) to production are: |
|  | Amorphous Si. Nanocrystalline thin film Si. Polycrystalline thin film Si. The CuInxGa1-xSe2 or "CIGS" family. The CdTe solar cell. May others in R&D |
|  | The present "high potentials" are CdTe and CIGS. |
| High-efficiency multi-junction solar cells may find applications as "concentrator cells" at the focus point of a large mirror or lens that tracks the sun. |
| CIGS and most other thin film solar cells have high internal resistances and need to be switches in series after about 1 cm for high performance |  |
|  | This must be done automatically and in-situ as part of the production process. |
|  | A whole new technology needs to be developed for thin film solar cell mass production |
| The race between bulk Si solar cells and thin film technologies is open in 2008; the winning technologies are to be determined. |
Exercise 8.3-2
All Quick Questions to 8.3

© H. Föll (Semiconductor Technology - Script)