By stabilizing perovskites in a supramolecular assembly, US researchers have created effective photoluminescent materials that can be made into thin films and 3D printer inks. The supramolecular approach simplifies the synthesis of the perovskites and could open the door to their broader use in light-emitting devices.
A research team led by Berkeley materials scientist Peidong Yang of the University of California has created supramolecular assemblies using crown ethers and hafnium- and zirconium-containing perovskites. The perovskites feature octahedral metal centers made of hafnium or zirconium bonded to six halide anions. These materials would normally be very air and moisture sensitive, but the use of crown ethers stabilizes them and allows for a much simpler synthesis protocol. Yang’s team developed a solution-based synthesis that occurs at 200°C, compared to the 1000°C solid-state reactions previously required to produce this type of perovskite.
Depending on whether a hafnium or zirconium perovskite is used, the supramolecular assemblies emit either blue or green light. The solid powders demonstrate an impressive photoluminescence efficiency of 96% with longer photoluminescence lifetime than other halide perovskite systems. The team created 3D printer inks from the materials by dispersing them in non-polar solvents. Dissolving polystyrene in the inks improved their processability. The team then used the inks to create various structures, including miniature light-emitting Eiffel Towers.