| 1 | Plants are extremely efficient converters of light into energy, more or less setting the bar for researchers creating photovoltaic cells that convert sunlight into electricity. | |
| 2 | Scientists in Germany used X-ray photoelectron spectroscopy to get a detailed image of the surface of a treated tooth. | |
| 3 | The most efficient silicon-based photovoltaic solar cells convert about 20 percent of the sunlight that strikes them into electricity. | |
| 4 | Off-grid energy systems such as photovoltaics, solar water heating, and on-site water collection can keep basic services going. | |
| 5 | "Look what happened to the photovoltaic industry," says Thomas Kautzsch, a partner at Oliver Wyman, a consultancy. |