Browsing by Author "Liang, Xiao"

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    Deterministic positioning of few aqueous colloidal quantum dots
    (Royal Society of Chemistry, 2024-08-27) Pambudi, Muhammad Tegar; Arora, Deepshikha; Liang, Xiao; Sain, Basudeb; Ranganath, Anupama Sargur; Chua, Matthew R; Vu, Cam Nhung; Zamiri, Golnoush; Rahman, Md. Abdur; Demir, Hilmi Volkan; Yang, Joel K. W.; Ding, Lu
    Emerging quantum technologies that critically require the integration of quantum emitters on photonic platforms are hindered by the control over their position, quantity, and scalability. Herein, we describe a facile strategy to deposit aqueous silica-coated quantum dots (QDs) in a template of polymethyl methacrylate (PMMA) nanoholes that leverages saturated ethanol vapor drop-casting and subsequent lift-off of the template. Ethanol vapor incorporation into water droplets during the drying process reduces the meniscus contact angle, which increases capillary forces and enhances particle confinement within the pinning contact region. Furthermore, induced Marangoni flow controls the particle transport dynamics inside the droplets, making large-scale deposition possible. Controlling the hole diameter of the template demonstrates changes in the number of QDs per hole, which is consistent with the Poissonian distribution with the best results of similar to 40% single-particle yield from an similar to 80% total site occupancy. This method employs a simple setup, eliminating the need for intricate optimization, yet offers the potential for deterministic patterning within complex photonic platforms.
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    ItemOpen Access
    Dual-Resonance nanostructures for color downconversion of colloidal quantum emitters
    (American Chemical Society, 2023-12-12) Ha, Son Tung; Lassalle, Emmanuel; Liang, Xiao; Do, Thi Thu Ha; Foo, Ian; Shendre, Sushant; Durmusoglu, Emek G.; Valuckas, Vytautas; Adhikary, Sourav; Paniagua-Dominguez, Ramon; Demir, Hilmi Volkan; Kuznetsov, Arseniy I.
    We present a dual-resonance nanostructure made of a titanium dioxide (TiO2) subwavelength grating to enhance the color downconversion efficiency of CdxZn1-xSeyS1-y colloidal quantum dots (QDs) emitting at ∼530 nm when excited with a blue light at ∼460 nm. A large mode volume can be created within the QD layer by the hybridization of the grating resonances and waveguide modes, resulting in large absorption and emission enhancements. Particularly, we achieved polarized light emission with a maximum photoluminescence enhancement of ∼140 times at a specific angular direction and a total enhancement of ∼34 times within a 0.55 numerical aperture (NA) of the collecting objective. The enhancement encompasses absorption, Purcell and outcoupling enhancements. We achieved a total absorption of 35% for green QDs with a remarkably thin color conversion layer of ∼400 nm. This work provides a guideline for designing large-volume cavities for absorption/fluorescence enhancement in microLED display, detector, or photovoltaic applications. © 2023 American Chemical Society.
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    ItemOpen Access
    Weakly confined organic-inorganic halide perovskite quantum dots as high-purity room-temperature single photon sources
    (American Chemical Society, 2024-04-10) Wang, Bo; Lim, Jia Wei Melvin; Loh, Siow Mean; Mayengbam, Rishikanta; Ye, Senyun; Feng, Minjun; He, Huajun; Liang, Xiao; Cai, Rui; Zhang, Qiannan; Kwek, Leong-Chuan; Demir, Hilmi Volkan; Mhaisalkar, Subodh G.; Blundell, Steven A.; Chien Sum, Tze
    Colloidal perovskite quantum dots (PQDs) have emerged as highly promising single photon emitters for quantum information applications. Presently, most strategies have focused on leveraging quantum confinement to increase the nonradiative Auger recombination (AR) rate to enhance single-photon (SP) purity in all-inorganic CsPbBr3 QDs. However, this also increases the fluorescence intermittency. Achieving high SP purity and blinking mitigation simultaneously remains a significant challenge. Here, we transcend this limitation with room-temperature synthesized weakly confined hybrid organic-inorganic perovskite (HOIP) QDs. Superior single photon purity with a low g((2))(0) < 0.07 +/- 0.03 and a nearly blinking-free behavior (ON-state fraction >95%) in 11 nm FAPbBr(3) QDs are achieved at room temperature, attributed to their long exciton lifetimes (tau(X)) and short biexciton lifetimes (tau(XX)). The significance of the organic A-cation is further validated using the mixed-cation FA(x)Cs(1-x)PbBr(3). Theoretical calculations utilizing a combination of the Bethe-Salpeter (BSE) and kp approaches point toward the modulation of the dielectric constants by the organic cations. Importantly, our findings provide valuable insights into an additional lever for engineering facile-synthesized room-temperature PQD single photon sources.