Scientists at MIT have developed a new approach to producing perovskite nanocrystals exactly where they are required, allowing them to be integrated into nanoscale devices. The technique means individual halide perovskite nanocrystals can be grown on-site with precise control over location to within less than 50 nanometers. Halide perovskites have excellent optoelectronic properties and possible applications in high-performance solar cells, light-emitting diodes and lasers.
Although already applied in thin-film macroscale and microscale devices, use of perovskites in on-chip nanoscale devices is limited since the material can be damaged in standard fabrication and patterning techniques. However, this platform allows the “growth” of halide perovskite nanocrystals directly onto a surface where the nanodevice will then be fabricatedwith accurate control over the location and size of each individual crystal. As the material is grown locally with the required features, conventional lithographic patterning steps that could introduce damage are unnecessary.
As reported in Nature Communications [Jastrzebska-Perfect et al. Nat. Commun. (2023) DOI: 10.1038/s41467-023-39488-0], here precise arrays of nanoscale light-emitting diodes (nanoLEDs), small crystals that emit light when electrically activated, were fabricated. The breakthrough could lead to applications in on-chip light sources, quantum light sources, photodetectors, lensless microscopy and high-resolution displays for augmented and virtual reality.
Central to this process was to localize the solution used in the nanocrystal growth. A nanoscale template was produced with small wells containing the chemical process through which crystals grow. The surface of the template and the inside of the wells were then modified, controlling its “wettability” so that a solution containing perovskite material wouldn’t pool on the template surface and be confined inside the wells. The team applied a solution containing halide perovskite growth material to the template and, as the solvent evaporates, the material grew and formed a tiny crystal in each well, with the shape of the wells being critical in controlling the nanocrystal positioning.
On the solvent evaporating inside the well, the nanocrystal experiences a pressure gradient that produces a directional force, with the specific direction being determined using the well’s asymmetric shape. As senior author Farnaz Niroui told Materials Today, “This approach provides a platform for high-throughput studies of perovskites at the nanoscale to elucidate their structure–chemistry–function relationships, in addition to enabling new applications in nanodevices.”
The platform could be used for other nanomaterials, and could also be extended to permit many other emerging device platforms such as lasers, photodetectors and memristors to be realized, and the team now hope to leverage the method to explore perovskites with optimal optoelectronic properties for light emission applications.
“This approach provides a platform for high-throughput studies of perovskites at the nanoscale to elucidate their structure–chemistry–function relationships, in addition to enabling new applications in nanodevices.”Farnaz Niroui
Precise arrays of nanoLEDs were fabricated