Browsing by Subject "Color Conversion"

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    Colloidal photonics of semiconductor nanocrystals: from polarized color conversion to efficient solar concentration
    (2018-07) Güngör, Kıvanç
    Effective photon management is pivotal to the success of future photonic applications. The demand for high-performance electronic displays and solar light harvesters has been increasingly growing, ever with high expectations in advancing their power efficiencies. Semiconductor nanocrystals are highly promising for use in such advanced photonic applications. However, conventional device architectures and fabrication methods cannot fully exploit their potential. To address the need for their effective utilization, in this thesis, we proposed and demonstrated novel photon managing methods for colloidal nanocrystals to target polarized color conversion and efficient solar concentration. Nanocrystals possess an unmatched color purity for next-generation displays but color enrichment in displays suffers from the inherent random polarization in their photoluminescence. Instead of clipping the undesired polarization, we show a new class of v-shaped backlight unit (v-BLU) creating Fano resonances to enforce isotropic quantum emitters of the integrated color-conversion nanocrystals to emit polarized light. While enabling a front-panel configuration, the proposed v-BLU of nanocrystals allows for a strong modification of the density of optical states via resonance coupling. This control over the density of states for isotropic quantum dots empowers the realization of high polarization contrast ratios while sustaining their optical transmission. Similar to color conversion, colloidal nanocrystals are also instrumental to light harvesting, in particular using atomically at nanocrystals with their step-like absorption profile making them potentially ideal candidates for luminescent solar concentrators (LSCs). Nevertheless, practically zero Stokes shift in their photoluminescence fundamentally limits their utilization. Here we overcame this limitation by proposing the doping of such colloidal quantum wells inducing a large Stokes shift with near-unity photoluminescence quantum efficiency. We developed and demonstrated high-performance LSC panels of the copper-doped quantum wells outperforming the LSCs of their undoped counterparts and doped quantum dots. The LSCs of such Cu-doped quantum wells offer record optical flux gain compared to other colloids. We believe that the findings presented in this thesis will advance the applications of colloidal nanocrystals boosting the performance of their next-generation photonic devices to unprecedented levels.
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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.