Browsing by Author "Shendre, Sushant"

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    Bright-dark exciton interplay evidenced by spin polarization in cdse/cdmns nanoplatelets for spin-optronics
    (American Chemical Society, 2025-01-08) Shornikova, Elena V.; Yakovlev, Dmitri R.; Tolmachev, Danil O.; Prosnikov, Mikhail A.; Christianen, Peter C. M.; Shendre, Sushant; Işık, Furkan; Delikanlı, Savaş; Demir, Hilmi Volkan; Bayer, Manfred
    Diluted magnetic semiconductor (DMS) colloidal nanocrystals demonstrate remarkable magneto-optical properties. The ability to control their magnetization and, consequently, the circular polarization of exciton emission holds significant potential for spintronic applications. However, the interplay between bright and dark exciton recombination and its impact on the polarization of emission are not yet fully understood. We measure the magneto-optical properties of colloidal CdSe/CdMnS nanoplatelets at cryogenic temperatures in high magnetic fields up to 30 T. The degree of circular polarization of photoluminescence demonstrates nonmonotonous behavior in a magnetic field. In low magnetic fields, the polarization degree is positive due to an exchange interaction of excitons with localized spins of magnetic Mn2+ ions. After reaching a maximum, the polarization degree starts to decrease and reverses the sign to negative in high magnetic fields, which is unusual in DMSs. The critical magnetic field, in which the sign is reversed, increases when the temperature is elevated. We develop a model that explains this behavior by an interplay of bright and dark exciton recombination. In high magnetic fields, the dark exciton radiative recombination rate accelerates due to mixing with the bright state, and the intrinsic Zeeman splitting of dark exciton overcomes the exchange with Mn2+ ions. As a result, the lowest |-2 > exciton energy level dominates in emission, providing negatively polarized photoluminescence.
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    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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    Management of electroluminescence from silver-doped colloidal quantum well light-emitting diodes
    (Cell Press, 2022-05-18) Liu, Baiquan; Sharma, Manoj; Yu, Junhong; Wang, Lin; Shendre, Sushant; Sharma, Ashma; Izmir, Merve; Delikanlı, Savaş; Altıntaş, Yemliha; Dang, Cuong; Sun, Handong; Demir, Hilmi Volkan
    Impurity doping is a promising strategy to afford colloidal nanocrystals exhibiting novel optical, catalytic, and electronic characteristics. However, some significant properties of noble metal-doped nanocrystals (NMD-NCs) remain unknown. Here, we report the electroluminescence (EL) from NMD-NCs. By doping silver impurity into cadmium selenide colloidal quantum wells (CQWs), dual-emission emitters are achieved and a light-emitting diode (LED) with a luminance of 1,339 cd m−2 is reported. In addition, the proposed energy gap engineering to manage exciton recombination is a feasible scheme for tunable EL emissions (e.g., the dopant emission is tuned from 606 to 761 nm). Furthermore, an organic-inorganic hybrid white LED based on CQWs is realized, reaching a color rendering index of 82. Moreover, flexible CQW-LEDs are reported. The findings present a step to unveil the EL property of NMD-NCs, which can be extended to other noble metal impurities, and pave the pathway for NMD-NCs as a class of electronic materials for EL applications. © 2022 The Authors