A research team led by Professor Maria Antonietta Loi at the University of Groningen has achieved a significant breakthrough in quantum dot technology, as described in their recent publication in Advanced Materials.
Quantum dots, clusters of approximately 1,000 atoms functioning as a single “super-atom,” offer customizable electronic properties through size adjustments. These dots, particularly those made of PbSe or PbS, can convert shortwave infrared light into electrical current—a valuable property for detector and telecommunication switch applications.
The primary challenge has been combining individual dots into functional materials without sacrificing their unique properties. Previous attempts resulted in either losing optical properties or poor charge carrier transport capabilities due to difficulties in creating ordered assemblies.
Professor Loi’s team developed an innovative self-organization method using a colloidal solution of quantum dots. By carefully depositing quantum dots onto a liquid “mattress,” they first created a two-dimensional ordered layer. Adding more dots transformed this into a three-dimensional structure. The dots, having a truncated cubic shape, self-oriented on the liquid surface to achieve a low-energy state, forming a superlattice.
This quantum dot superlattice demonstrates unprecedented electron mobility while maintaining the optical properties of individual dots. Using advanced imaging techniques available at the Zernike Institute—electron microscopy with atomic resolution and Grazing-incidence small-angle X-ray scattering—the team confirmed both the detailed structure and large-scale organization of the material.
The resulting metamaterial exhibits bulk semiconductor electronic behavior while preserving the optical characteristics of individual dots. This innovation opens pathways for creating infrared optical switches for telecommunications and infrared detectors for night-vision and autonomous driving technologies.
Professor Loi noted that scientists have pursued this goal since the 1980s, making this achievement particularly significant. The control of structure and properties exceeded the team’s expectations. Building on this success, Loi recently received an Advanced Grant from the European Research Council to explore extended superlattices using various building blocks, with immediate plans to refine the technique for creating more perfect materials and fabricating photodetectors.
Reference: Jacopo Pinna, Razieh Mehrabi K., Dnyaneshwar S. Gavhane, Majid Ahmadi, Suhas Mutalik, Muhammad Zohaib, Loredana Protesescu, Bart J. Kooi, Giuseppe Portale, Maria Antonietta Loi. Approaching Bulk Mobility in PbSe Colloidal Quantum dots 3D Superlattices. Advanced Materials, 2022; 2207364 DOI: 10.1002/adma.202207364
