A fabrication process with improved light-conversion efficiency for solar cells based on films of hybrid perovskite - a crystalline structure created from organic and inorganic materials - is reported online this week in Nature Materials. These results provide a step forward in creating highly efficient low-cost perovskite solar cells.

Perovskite solar cells are moving rapidly towards the 20%-25% efficiency that silicon-based photovoltaic cells have. One advantage of these types of cell is that perovskite can be deposited from a solution, which potentially allows for the fabrication of these devices with printing tools. However, solution-based processes usually create small, non-uniform perovskite grains; a morphology that limits the efficient collection of the electric charges generated in the film by light exposure.

Sang Il Seok and colleagues optimized the sequence in which solvents are added during the deposition process, resulting in an intermediate crystalline compound that turns into a dense and uniform film on heating. This led to a power-conversion efficiency exceeding 16%, which is higher than previous values for perovskite solar cells reported in the scientific literature. Moreover, the architecture of the new devices avoids performance issues that may have led to the overestimation of the efficiency of some previous perovskite solar cells.