A new technique has been developed to generate perovskite nanocrystals precisely at their required locations, enabling seamless integration of these highly fragile materials into nanoscale devices.
Halide perovskites, with exceptional optoelectronic properties, are interesting for solar cells, LEDs, and lasers. While primarily used in thin-film or micron-sized devices, nanoscale integration offers exciting possibilities like on-chip light sources, photodetectors, and memristors. Yet, challenges persist due to susceptibility to damage from conventional fabrication techniques.
MIT researchers have created a technique for the on-site growth of individual halide perovskite nanocrystals, enabling precise location control within a range of less than 50 nanometers. Nanocrystal size is controlled precisely, impacting characteristics. Local growth eliminates damaging lithographic steps. The scalable technique integrates nanocrystals into nanodevices. The researchers used this technique to make nanoLED arrays for optical communication, computing, microscopes, quantum light sources, and AR/VR displays.
Tiny crystals, huge challenges
Integrating halide perovskites into nanoscale devices is challenging. The researchers have two different approaches. One was fragile perovskite film patterned with solvent-based lithography; the other was smaller crystals picked and placed in the desired pattern. Limited control, resolution, and integration in both cases hinder material extension to nanodevices. Instead, the researchers “grow” halide perovskite crystals directly onto the desired surface for nanodevice fabrication. Their process localizes the solution for nanocrystal growth by creating a template with wells, modifying its surface and the wells’ interiors to control “wettability” and confine the perovskite solution inside. They apply a perovskite growth solution to the template, and as the solvent evaporates, tiny crystals form in each well.
A versatile and tunable technique
The researchers found that the well’s shape is crucial for nanocrystal positioning. Square wells result in an equal chance of crystals in each corner. Well-shape manipulation creates directional forces based on pressure gradient and asymmetric shape for precise placement. The team has achieved high precision in both growth and nanocrystal placement. The researchers found they could control the crystal size by adjusting well size. Varying growth solution volume creates larger or smaller crystals. Precise nanoLED arrays were made, serving optical communication, computing, quantum light sources, microscopy, and high-resolution displays for augmented and virtual reality.
The researchers plan to explore more applications, test device miniaturization limits, and integrate with quantum systems. The process offers opportunities for halide perovskite-based on-chip nanodevices. It facilitates material study at the nanocrystal level, inspiring further research on unique materials.
