Masaru K. Kuno

Research Interests

Nanoscience and nanotechnology are premised on exploiting the size- and shape-dependent optical, electrical, and chemical properties of materials for applications. Among proposed applications of nanostructured semiconductor materials are light emitting, light harvesting, and cooling. At microscopic scales, local variations in optical, electrical, and chemical responses exist, and these can be used to characterize material properties.

The Kuno Group has therefore developed microscopic approaches for probing material behavior on small length scales. This has entailed conducting some of the first single nanostructure extinction experiments. The importance of being able to probe extinction as opposed to emission lies in the fact that many materials are not particularly emissive. Consequently, they are effectively invisible to existing single particle and single molecule optical measurements based on photoluminescence. More recent single nanostructure absorption studies have focused on conducting experiments in the mid-infrared “fingerprint” region of the spectrum. This enables ultrasensitive, chemically specific imaging and spectroscopy of individual nanostructures and other materials such as micro/nanoplastics.

Another important theme in our research involves unravelling the photophysics of important materials. One example involves mixed-halide hybrid perovskite materials used in solar energy conversion, e.g., tandem perovskite/silicon solar cells. Despite record setting solar power conversion efficiencies, the mixed-halide perovskite active layers of such devices are subject to unwanted, light-induced halide photosegregation. Understanding these intrinsic material instabilities is crucial for eventually commercializing perovskite-based devices. Efforts have therefore been made to develop a microscopic model of light-induced halide photosegregation using detailed optical studies of photosegregation coupled to theory.

Finally, a long term goal is to realize the optical refrigeration of semiconductors. The concept was first conceived in 1929 and is based on the simple premise that photoluminescence up-conversion can remove heat from materials. Preventing realization of this concept, however, are material quality issues that lead to irradiation-induced heating overwhelming cooling. We have focused on solving these material quality issues and on developing a fundamental understanding of photoluminescence up-conversion so that this vision of cryogen free optical refrigeration can eventually be realized.

Research in the Kuno group is intrinsically interdisciplinary and spans areas such as physical chemistry/chemical physics, materials chemistry, inorganic chemistry, and even device chemistry/physics.

Selected Publications

• Ghonge, S.; Engel, D.; Mattiotti, F.; Celardo, G. L.; Kuno, M. and Janko, B. "Enhanced Robustness and Dimensional Crossover of Superradiance in Cuboidal Nanocrystal Superlattices" 2023 Physical Review Research, 5 (2), 023068. DOI: 10.1103/PhysRevResearch.5.023068.
• Ding, Y.; Zhang, Z. M.; Toso, S.; Gushchina, I.; Trepalin, V.; Shi, K. J.; Peng, J. W. and Kuno, M. "Mixed Ligand Passivation as the Origin of Near-Unity Emission Quantum Yields in CsPbBr3 Nanocrystals" 2023 Journal of the American Chemical Society, 145 (11), pp.6362-6370. DOI: 10.1021/jacs.2c13527.
• Kniazev, K.; Guo, T. L.; Zhai, C. J.; Gamage, R. S.; Ghonge, S.; Frantsuzov, P. A.; Kuno, M. and Smith, B. "Single-Molecule Characterization of a Bright and Photostable Deep-Red Fluorescent Squaraine-Figure-Eight (SF8) Dye" 2023 Dyes and Pigments, 210, 111031. DOI: 10.1016/j.dyepig.2022.111031.
• Gushchina, I.; Trepalin, V.; Zaitsev, E.; Ruth, A. and Kuno, M. "Excitation Intensity- and Size-Dependent Halide Photosegregation in CsPb(I0.5Br0.5)3 Perovskite Nanocrystals" 2022 ACS Nano, 16 (12), pp.21636-21644. DOI: 10.1021/acsnano.2c10781.
• Toso, S.; Gushchina, I.; Oliver, A. G.; Manna, L. and Kuno, M. "Are Mixed-Halide Ruddlesden-Popper Perovskites really Mixed?" 2022 ACS Energy Letters, 7 (12), pp.4242-4247. DOI: 10.1021/acsenergylett.2c01967.
• Mathew, P. S.; Szabo, G.; Kuno, M. and Kamat, P. V. "Phase Segregation and Sequential Expulsion of Iodide and Bromide in Photoirradiated Ruddlesden-Popper 2D Perovskite Films" 2022 ACS Energy Letters, 7 (11), pp.3982-3988. DOI: 10.1021/acsenergylett.2c02026.