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Welcome to my Research Portal
Welcome to my Research Portal
I specialize in halide perovskites, quantum dots, and their various optoelectronic applications, such as microlasing, light emission sources, and solar cells. During my PhD, I have dedicated the past five years to experimental research, exploring these advanced materials' fundamental properties and applications. This website provides a platform to share my insights, research findings, and innovative methodologies, offering a deeper look into my projects and publications. Join me in exploring perovskite materials and next-generation photonic devices.
Scientific Artwork
Scientific Artwork
Nano vineyard: TiO2 microspherical particles on the edge of the silica substrate
Second Place in MRS Spring Meeting & Exhibit 2025
Colours of quantum world: Quantum dots on TiO2 spheres
Colours of quantum world: Quantum dots on TiO2 spheres
Nano Sun: TiO2 microsphere on silica substrate
Research Highlights
Research Highlights
Lead halide perovskites (LHPs) have garnered significant attention due to their exceptional optical and electronic properties. The tunable bandgaps and high absorption coefficients of LHPs enable the design of high-efficiency solar cells that can capture a broader spectrum of sunlight. Additionally, their excellent charge carrier mobility and solution-processability make them ideal for creating flexible and lightweight solar panels. In photodetectors, perovskite QDs offer high sensitivity and fast response times, making them suitable for applications in imaging, sensing, and communication technologies. Furthermore, LHPs high PLQY can be utilized to exhibit promising lasing behaviour, essential for developing advanced photonic devices. These properties make LHPs suitable for various optoelectronic applications, including solar cells, light-emitting diodes (LEDs), lasers, and photodetectors.
Ultrahigh quantum yield, bandgap tunability and high absorption coefficient makes CsPbI3-xBrx perovskites ideal candidates for various optoelectronic applications. Post synthesis mixing of CsPbI3 and CsPbBr3 nanocrystals (NCs) is an effective approach to tune the optical properties of CsPbI3-xBrx NCs. The ion mixing mechanism in these perovskite NCs have been of great interest, as they shed valuable insights on how the halide ions get exchanged between the neighbouring NCs. The exchange, mixing and alloying of halide ions between NCs are influenced by various parameters controlling these reactions. In this study we report two contrasting pathways, depending on the aging of the NCs, by which the halide ions get exchanged between the CsPbI3 and CsPbBr3 NCs. Changes in the photoluminescence spectra are monitored as a function of time to understand the dynamical changes in composition when CsPbBr3 and CsPbI3 NCs are mixed immediately after preparing and after aging for 40 days. Mixing of freshly synthesized CsPbBr3-NCs and CsPbI3-NCs in various ratios (2:1, 1:1 and 1:2) lead to both the Br⁻ and I⁻ ions getting rapidly incorporated into the CsPbI3 and CsPbBr3 NCs, respectively, as well as nucleation and growth of mixed halide composition, before the final equilibrium phase is formed. On the contrary, when 40 days aged NCs of CsPbBr3 are mixed with CsPbI3, the diffusion of ions seems to proceed in two-pathways, with the I⁻ ions from CsPbI3 NCs primarily dissolve and get incorporated into the CsPbBr3 lattice and equilibrium phase formation by nucleation, while Br⁻ ions do not incorporate into the CsPbI3 lattice. This more controlled reaction in aged samples is likely due to changes in surface chemistry of NCs, such as the formation of a robust ligand shell on CsPbI3-NCs, which allows one way ion exchange.
TiO2 microspheres encapsulated with photostable Cs0.5Rb0.5PbBr3 quantum dots (QDs) are shown to exhibit whispering gallery mode (WGM) microcavity lasing. Cs0.5Rb0.5PbBr3-QDs have high photostability and photoluminescence quantum yield (PLQY) compared to CsPbBr3 and CsPbI3 QDs. A strong synergy between TiO2 optical microcavity and the PL emission from Cs0.5Rb0.5PbBr3-QDs serving as the gain medium is evidenced from the WGM-less, spontaneous emission arising at a low excitation laser power transitioning to a stimulated lasing emission characteristics of WGM modes beyond the critical threshold of 7.98 kW/cm2. Upon excitation with an Ar-ion laser (λex = 488 nm), a substantial amplification exceeding an order of magnitude is observed at this threshold. The WGM lasing in this system exhibits a high-quality factor (Q) of ~1807 at room temperature. Remarkably, the WGM lasing maintains photostability, with no discernible photodegradation even under elevated continuous laser power of ~20.03 kW/cm2 for 90 minutes. WGM lasing is also observed in coupled doublet and triplet microspheres; however, the Q-factor decreases as the number of coupled microcavities increases. Rb-substituted halide QDs show potential for photostable, tuneable WGM microlaser applications.
Whispering gallery mode (WGM) lasing in CsPbI3 quantum dots (QDs) coated on TiO2 spherical microcavities is demonstrated. The photoluminescence emission from CsPbI3-QDs gain medium strongly couples with TiO2 microspherical resonating optical cavity. Spontaneous emission in these microcavities switches to a stimulated emission above a distinct threshold point of 708.7 W/cm2. Lasing intensity increases three to four times as the power density increases by one order beyond the threshold point when the microcavities are excited with a 632 nm laser. WGM microlasing with quality factors as high as Q~1195 is demonstrated at room temperature. Quality factors are found to be higher for smaller TiO2 microcavities (~2 mm). CsPbI3-QDs/TiO2 microcavities are also found to be photostable even after continuous laser excitation for 75 minutes. The CsPbI3-QDs/TiO2 microspheres are promising as WGM based tunable microlasers.
Copyright (C), Subitan Laskar, All rights reserved.
Copyright (C), Subitan Laskar, All rights reserved.
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