 Did you know that we can solve the entire world's energy demand by covering an area of 350,000 square kilometers with solar panels? You might not have a feeling about how large an area this is, but they're actually less than 0.1 percent of the surface of Earth. And it compares to our neighbor countries, Sweden, Germany, even Norway. Maybe we should take a vote about which country we can spare, joking aside. In my research group, we aim to minimize this area by enhancing the efficiency of a silicon-based solar cell. To understand how this works, we need to have a basic understanding of energy conversion in a solar cell. So as many of you might know, the sun emits in many colors what we in physics denote as wavelengths. And only some of these wavelengths can be absorbed in silicon. In the graph behind me, I've shown the solar spectrum. In green, you see the part that can be absorbed in silicon, and in red, the part that cannot be absorbed. This red part amounts to 20 percent of the light from the sun. So there's a lot of energy here that we can harvest. In my research group, we aim to do this by process called up conversion. Up conversion is the process of combining two photons, light particles, to one of higher energy. And we can do this in the element erbium, since erbium has the ability to absorb two photons at 1500 nanometers and emit one at 980 nanometers. That's actually a coincidence with the most efficient region for a silicon-based solar cell. Unfortunately, this process is very inefficient, since erbium is a poor absorber. But luckily, we can enhance the process by focusing the light, since the process involves the absorption of two photons at once. And then instead of placing a large lens in front of the up converting sample, we structure the surface with the metal nanostructures. And if these are shaped correctly for the incoming light, they can interact and create a resonance phenomenon that greatly enhances the light in this up converting sample and hereby enhances the up conversion in erbium. Recently, in my research group, we have been able to measure a world record baking 850-fold enhancement of the up conversion process. And hopefully in the future, we will be able to see high efficient solar cells with this technique incorporated. Thank you for your time.