 We're at the beginning of a fundamental transition in the way we use energy. We have an urgent need to reduce carbon dioxide emissions and at the same time, we need to provide for the growing energy demand around the world. In order to meet that demand, we need to produce as much power by 2050 as we currently are producing now and we need to do it with clean energy. The solution to this is solar energy. We have an enormous solar resource. We can power the entire world using only 1% of the Earth's surface with solar energy. In fact, we can power the entire world using only a small fraction of Australia, as you can see in the picture. In the 1970s, solar power cost around $100 per watt. It's now less than 50 cents per watt. So it's fallen in price by a factor of around 200 over the last 40 years. As a result, the amount of solar being installed has increased exponentially. We've now reached a point where solar power has overtaken the amount of wind power being installed. If you put wind and solar together, there's now more new wind and solar being installed each year than new fossil fuels. So we've really reached the point of the energy transition. As a result of all this, solar energy is now really big business. Factories are being installed, which are producing power on the gigawatt scale. But if we want to accelerate the energy transition, we need to keep driving down the cost of solar power. This is the way that we need to go. In order to achieve that, what we need to do is to increase the efficiency of solar systems. The reason for that is if you have higher efficiency, then you can produce the same power with a smaller system. And a smaller system uses less materials, less glass, and so overall the cost can be lower. So in my lab, what we're doing is using new materials to increase the efficiency of solar power. The reason for this is the standard material used in solar cells is silicon, which is the material used in silicon chips. But silicon solar cells don't use blue light very efficiently. They use red light very efficiently, but the blue light has extra energy, and that extra energy is just wasted in standard solar cells. The solution to this is to put a new solar cell on top of the silicon solar cell that's efficient at absorbing the blue light. So it can absorb the blue light. It can produce a higher voltage. You can put it together with the silicon solar cell, and overall you can get a higher efficiency for the system. The material that we're using for these higher efficiency solar cells is perovskites. So perovskite materials are very efficient at absorbing the blue light from the solar spectrum. They can absorb the blue light. They can allow an electron to transfer, and then you can put them on top of the silicon solar cell, and you can produce a system that has higher efficiency overall. The advantage of perovskite materials is that they're also very easy to process. You can actually print these materials starting from a solution at room temperature. So you can print the materials onto glass, and so you have a very nice low-cost process for making the solar cells. So what we're doing in my lab is putting the perovskite cells on top of the silicon solar cells. We've achieved an efficiency of 26% with this stack system, and which is the highest efficiency that's been achieved with this type of system. And importantly, it's been the only way that's been shown to increase the efficiency of solar cells using a low-cost process. Now, perovskites do have their limitations. The main one is stability. They're sensitive to heat and also to moisture. In contrast, silicon is basically like a rock. If nothing will happen to it once you've done the processing. The perovskite materials, they're very easy to process, but that means they're also sensitive. What we've done, though, is to engineer the composition of the perovskite solar cell, and we've been able to show that you can increase the efficiency and the stability by engineering the composition of the material. It's not the only thing you need to do. You also need to encapsulate the material to keep it sensitive. Overall, I've shown that there's an enormous solar resource. We've seen a dramatic reduction in the costs of solar energy over recent years. We've seen a dramatic escalation of the amount of solar being installed to the point where wind and solar to combined are now higher installed overall than other types of solar power. Putting all this together, we can imagine a future where solar energy can provide abundant energy for everyone. We're already at the point where this is happening, where solar energy is not only efficient and clean, but it's going to be the dominant technology because it's also the cheapest.