Perovskite solar cells have come a long way in a short period of time, but there is still room for improvement. Engineers have now added a layer of quantum dots to the recipe to create a more stable solar cell with near-record efficiency. It is understood that there are several reasons for making efficient solar cells with perovskite materials. Their films efficiently absorb the entire spectrum of visible light and are inexpensive to manufacture, lightweight and flexible. But there's a catch: Perovskite solar cells have stability issues and degrade under real-world conditions, and their efficiency tends to drop as the cell area increases. In past studies, scientists have tried to improve stability by adding macromolecules, old pigments, two-dimensional additives, or capsicum compounds. In the new study, researchers from the Ecole Polytechnique Fédérale de Lausanne (EPFL) and the Korea Energy Research Institute tested a new ingredient, quantum dots. These tiny particles emit a specific color of light when illuminated, and are already starting to find applications in things like televisions and solar cells. The research results were published in the journal Science.
In this case, the team used quantum dots made of a type of tin oxide as the electron transport layer of the device. This layer shuttles the electrons produced by the perovskite into the electrode, so the energy can be harnessed. Compared to the common titanium dioxide material from which the layer is made, quantum dots improve the device's ability to trap light and reduce the reactions that sometimes occur between the two layers, which often reduces efficiency. All in all, the team found that the perovskite solar cell with the quantum dot layer achieved an efficiency of 25.7 percent, just 0.1 percent below the current record of 0.08 square centimeters. The efficiency of the larger solar cells was also good: the team recorded efficiencies of 23.3% for the 1-cm² cell, 21.7% for the 20-cm² cell, and 20.6% for the 64-cm² cell.
