Perovskite solar cells have made great progress in a short time, but there is still room for improvement. Engineers have now added a layer of quantum dots to the formula to create a more stable solar cell with near-record efficiency.
It is understood that there are several reasons for using perovskite materials to make effective solar cells. Their thin films can effectively absorb the entire spectrum of visible light, and have low manufacturing cost, light weight and good flexibility.
But there is a problem: perovskite solar cells have stability problems and will degenerate under real conditions, and their efficiency often decreases with the expansion of cell area. In past studies, scientists have tried to improve stability by adding molecules, old pigments, two-dimensional additives or pepper compounds.
In the new study, researchers at the (EPFL) of the Lobsang Federal Institute of Technology and the Korea Energy Institute tested a new ingredient, quantum dots. These tiny particles emit light of a specific color when they are irradiated and have begun to be used in fields such as televisions and solar cells. The study was published in the journal Science.
In this case, the team used quantum dots made of tin oxide as the electron transport layer of the device. This layer shuttles electrons from perovskite to the electrode so that energy can be used. Compared with the commonly used titanium dioxide materials used to make this layer, quantum dots improve the device's ability to capture light and reduce the reaction that sometimes occurs between the two layers, which usually reduces efficiency.
All in all, the team found that perovskite solar cells with quantum dots were 25.7% efficient, only 0.1% lower than the current record high of 0.08 square centimeters. The efficiency of larger solar cells is also good: the team recorded an efficiency of 23.3% of a square centimeter cell, 21.7% of a 64 square centimeter cell, and 20.6% of a square centimeter cell.
