Metal halide perovskites (hereinafter perovskites) are one of the typical representatives of new semiconductor materials. They have shown great development potential and application prospects in the field of optoelectronic devices.
However, perovskites lack stability and are susceptible to degradation at crystallographic defects, such as grain boundaries, and usually exhibit other problems of strong ion migration and structural/electrical instabilities. The study of single-crystal perovskite is still in its infancy, mainly due to their uncontrollable crystal synthesis and bulky size, which make them difficult to be integrated into electronics.
To address these problems, Yusheng Lei, a postdoctoral fellow at Stanford University, has carried out a series of original works in three aspects: crystal preparation, property research, and device integration of single-crystal perovskites. His work has solved the problems that the field could not solve in the past decade, and greatly promoted the research process of single-crystal perovskite devices.
Lei has been interested in scientific experiments since he was a child, so he entered the laboratory to participate in a number of scientific research projects during his undergraduate period, and then went to the University of California, San Diego to pursue a Ph.D. degree with the mentality of learning advanced technology.
During Yusheng’s Ph.D. research, he demonstrated a patterned epitaxial growth of single-crystal metal halide perovskites with the designed morphology and orientation. The first demonstration of a high-efficiency micro-LED array of interest for displays was realized, which is the first report to bring the metal halide perovskites into micro-electronics.
Moving to the growth of the single-crystal perovskite on an unlike substrate, Lei was able to show that a very promising but metastable organic-inorganic halide perovskite (CH (NH2)-2PbI3) could be grown heteroepitaxially, where the substrate-induced strain stabilizes the thin film, alters the carrier dynamics, and improves the device (photodetector) performance.
Finally, Lei proposed an ultrathin crystal film formation and lift-off procedure to lead to the successful fabrication of single-crystal flexible devices. He demonstrated this to great effect by creating graded junction halide perovskite solar cells.
The whole procedure not only solved the long-term challenges of fabricating ultra-thin single-crystal thin films in this field, but the as-integrated single-crystal flexible solar cells also achieved the world's highest efficiency of the tripartite certification of monocrystalline solar cells with excellent stabilities, providing potential possibilities for the energy supply of wearable electronic devices. His work also opens up the possibility of transformational change in solar cells, display, photodetection, and medical imaging technology.
In the future, Lei plans to further simplify the manufacturing process of single-crystal perovskite devices, explore more potential factors for improving stability, and look for solutions for increasing stretchable transistor performance and integration.
