Demystifying the Exciton-Dopant Interaction in Lead Halide Perovskites by Magneto-Optical Spectroscopy on Single Nanocrystals

• Applicant: Dr. Pradeep Kodimana Ramakrishnan
• Subject Area: Experimental Condensed Matter Physics ; Synthesis and Properties of Functional Materials
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 515545208

Perovskite nanocrystals (NCs) based on lead halides, both in their hybrid organic-inorganic MAPbX3 (MA=CH3NH3; X=Cl, Br, I) chemical composition and in the completely inorganic form of lead and caesium halides (CsPbX3), have recently emerged as potential candidates in a variety of optoelectronic and photon technologies, extending from photovoltaic cells to light emitting diodes and lasers. Like in chalcogenide nanocrystals, the optical properties of perovskite NCs can be adjusted by controlling size, shape, and composition. Through this emission spectra across the entire visible spectrum can be obtained. In a new endeavour, transition metal doping, e.g, with Mn2+, was recently introduced to perovskite nanocrystals. The interest in doped perovskite NCs has been focused largely on the efficiency of dopant emission, the spectral tunability of the luminescence, and on the emergence of dual emission. Although several studies are done to unravel the mechanism of dopant emission, there are still a variety of important open questions, especially concerning the interaction between manganese spins and the excitons, in these confined systems. To fill this gap, we will study the mechanism of dopant sensitization using single nanocrystal spectroscopy on purposefully selected Mn2+ doped perovskite nanocrystals. We indent to understand the role of exciton fine structure on the energy transfer from the perovskite host nanocrystals to the dopant and investigate the role of exciton-dopant interaction on the dopant sensitization. For this, magnetic field dependent experiments will be conducted on individual nanocrystals with various dopant concentration, halide composition, and targeted quantum confinement. By extracting the g-factor in single nanocrystals experiments, the hypothesis that sp-d exchange interactions can be increased by introducing quantum confinement of the host will be proven or discarded.

• DFG Programme: WBP Position