Optimization of transparent and reflecting electrodes for amorphous silicon solar cells
Abstract
In this research, hydrogenated amorphous silicon (a-Si:H) films were deposited by an inexpensive, thermally induced, atmospheric-pressure chemical vapor deposition (CVD) process. High-quality films were grown at 300 A, more than two orders of magnitude faster than those produced by conventional glow discharge. Sources of uncontrolled oxygen, boron, phosphorus, and carbon contamination were identified and eliminated. The efficiency of a-Si solar cells can be increased by using rough, rather than smooth, tin oxide as the front-surface transparent electrode, because the rough tin oxide-silicon interface increases the absorption of red light (light trapping) and reduces the reflection loss of light across the whole spectrum. We produced, by CVD, rough tin oxide films from tetramethyltin. Cells grown on the rough films have higher efficiencies than those grown on smooth tin oxide. We also used a precursor tin compound (dimethyltin dichloride) that is less costly and less hazardous than others. Rough films can be grown from dimethyltin dichloride more than three times faster than from tetramethyltin. To combine the CVD processes we need a layer that prevents the tin oxide layer from being attacked by the silicon, such as a barrier layer of titanium oxide, which seems to be effective.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- June 1988
- Bibcode:
- 1988STIN...8911316G
- Keywords:
-
- Amorphous Silicon;
- Electrodes;
- Optimization;
- Oxide Films;
- Reflection;
- Transparence;
- Boron;
- Carbon;
- Hydrogenation;
- Oxygen;
- Phosphorus;
- Photovoltaic Cells;
- Solar Cells;
- Thin Films;
- Tin Oxides;
- Vapor Deposition;
- Energy Production and Conversion