"The performance of perovskites in solar cells has really taken off in recent years, and they have properties that give them a lot of promise for LEDs, but the inability to create uniform and bright nanoparticle perovskite films has limited their potential," said assistant professor Barry Rand.
"Our new technique allows these nanoparticles to self-assemble to create ultra-fine grained films, an advance in fabrication that makes perovskite LEDs look more like a viable alternative to existing technologies.”
Perovskites exhibit a number of properties – they can be superconductive or semiconductive, depending on their structure – that make them promising materials for use in electrical devices.
Hybrid organic-inorganic perovskite layers are fabricated by dissolving perovskite precursors in a solution containing a metal halide and an organic ammonium halide.
However, while the resulting semiconductor films could emit light in vivid colours, the crystals forming the molecular structure of the films were too large, which made them inefficient and unstable.
The Princeton team reports that the use of an additional type of organic ammonium halide, and in particular a long-chain ammonium halide, to the perovskite solution during production constrained the formation of crystals in the film. The resulting crystallites were much smaller than those generated with previous methods, and the halide perovskite films were far thinner and smoother.
This led to better external quantum efficiency, meaning the LEDs emitted more photons per number of electrons entering the device.