Researchers at Princeton University have developed a technique in which nanoscale perovskite particles self-assemble to produce more efficient, stable and durable perovskite-based LEDs. This advance could speed the use of perovskite technologies in commercial applications such as lighting, lasers and television and computer screens.
The team explains that this technique allows nanoparticles of perovskite to self-assemble to create ultra-fine grained films, an advance in fabrication that could make perovskite LEDs a viable possibility.
LEDs operate best when the received current can be strictly controlled. In the devices fabricated in this work, the thin nanoparticle-based films allowed just that. The team is exploring perovskites as a potential lower-cost alternative to gallium nitride (GaN) and other materials used in LED manufacturing.
Hybrid organic-inorganic perovskite layers are fabricated by dissolving perovskite precursors in a solution containing a metal halide and an organic ammonium halide. It is a relatively cheap and simple process that could offer an inexpensive alternative to LEDs based on silicon and other materials. However, while the resulting semiconductor films could emit light in vivid colors, the crystals forming the molecular structure of the films were too large, which made them inefficient and unstable.
In this new paper,the 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 dramatically constrained the formation of crystals in the film. The resulting crystallites were much smaller (around 5-10 nanometers across) 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. The films were also more stable that those produced by other methods.