Research
Synthesis and Characterization of Metal Halide Perovskites Nanostructures
I synthesize all-inorganic (Cs-based) and organic-inorganic hybrid (MA-, and FA-based) lead and lead-free (Sn-, and Bi-based) halide perovskite (2D and 3D) nanocrystals and nanosheets using hot injection and ligand-assisted reprecipitation methods. A scheme for the synthesis of these nanostructures is shown above. I characterize them using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and fluorescence optical microscopy. Halide perovskites are highly promising for solar cells, lasers, LEDs, photodetectors, and catalysis.
Synthesis and Characterization of Metal Halide Perovskite Single Microcrystals
I synthesize lead halide perovskite single microcrystals using the anti-solvent vapor-assisted crystallization method. I prepare ABX3-type single crystals and characterize them using the techniques mentioned above. These microcrystals are studied for lasing properties, defect passivation, and photon reabsorption. The figure shows MAPbBr3 microrod and microplate which shows lasing above a threshold excitation intensity.
Optoelectronic Properties, Energy and Charge Transfer
I study the optoelectronic properties, energy transfer, and charge transfer in metal halide perovskites using time-resolved and steady-state photoluminescence spectroscopy, UV-visible absorption spectroscopy, and transient absorption spectroscopy. The figures show steady-state fluorescence spectra of CsPbX3 perovskite nanocrystals and time-resolved fluorescence decay profiles of these nanocrystals, both with different halide ion compositions (X=Cl, Br, I). These nanocrystals show high fluorescence quantum yield (>60%) and can be used for multi-color backlight display devices and LEDs.
MAPbI3 blinking.aviSingle-particle PL Blinking, Blinking Suppression, and Defect Passivation
Lead halide perovskite nanocrystals and quantum dots show photoluminescence blinking, owing to the presence of halide vacancy defects in them. Such vacancy defects are passivated by treating the samples with excess halide ions, and PL blinking can be suppressed. This strategy is useful for obtaining stable and high quantum yield nanocrystals and high-efficiency LEDs. The video shows PL blinking in MAPbI3 perovskite nanocrystals, while the figure shows real-time PL blinking time trajectories before and after defect passivation.