Demystifying the Exciton-Dopant Interaction in Lead Halide Perovskites by Magneto-Optical Spectroscopy on Single Nanocrystals
Synthesis and Properties of Functional Materials
Final Report Abstract
Cesium lead halide perovskites exhibit excellent optical and electronic properties, making them suitable for a wide range of optoelectronic applications, such as light-emitting devices. Doping impurity ions into semiconductor luminescent materials provides a unique method for inducing emission centers and enabling photoluminescence tuning. Among various luminescent materials, Mn2+ doped metal halide perovskites have garnered significant attention due to their simple synthesis procedure, which leads to high-quality orange-emitting nanocrystals. While most research has focused on the efficiency of dopant emission and the spectral tunability of luminescence, little attention has been given to understanding the host-dopant energy transfer mechanism. To address this gap, our work focused on studying the mechanism of dopant sensitization using single nanocrystal spectroscopy on Mn-doped perovskite nanocrystals. We aim to understand the role of exciton fine structure in the energy transfer process between the perovskite host and the dopant and investigate how exciton-dopant interactions affect dopant sensitization. Single-particle photoluminescence spectroscopy experiments were conducted on individual nanocrystals with varying dopant concentrations and compositions. Our preliminary results indicate that colloidal Mn2+ doped CsPbCl3 nanocrystals, prepared via the hot injection method, exhibit high photoluminescence quantum yields (PLQYs) of 30-50% and dual emission in the blue and orange spectral range. These nanocrystals are stable over several months, as evidenced by consistent photoluminescence emission and decay lifetime data measured over a six-month period. For single nanocrystal spectroscopy, diluted samples were spin-coated onto silicon substrates. This resulted in emission spectra changing from broad, unstructured emission in nanocrystal ensembles to narrow emission lines (0.8 meV) from isolated single nanocrystals. However, we observed a significant drop in dopant emission intensity after dilution, with only the excitonic photoluminescence fine structure being visible. We aim to leverage the tunability of perovskite materials and the magnetic properties of dopants to tailor exciton-dopant interactions for potential spin-based optoelectronic applications.
