Browsing by Author "Ersundu A.E."

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    The synergistic effect of Er3+and Ho3+on temporal color tuning of upconversion emission in a glass host: Via a facile excitation modulation technique for anti-counterfeiting applications
    (Royal Society of Chemistry, 2020) Erol E.; Kibrisli O.; Vahedigharehchopogh N.; Çelikbilek Ersundu M.; Ersundu A.E.
    Lanthanide-doped upconversion luminescent materials are highly promising for diverse applications, e.g., solid-state lighting, volumetric displays, and anti-counterfeiting, owing to their unique optical feature of color-tunable emission under near-infrared excitation. Hence, in this study, emission color tuning of Er3+/Ho3+ ions in a fixed glass host is investigated via a facile excitation modulation technique. The upconversion emission color from green to yellowish is tuned successfully by regulating the frequency of the irradiation source. The population and depopulation rates of related transitions are investigated through time-resolved photoluminescence and Judd-Ofelt analysis in order to elucidate the proposed mechanism of color tuning. Upconversion quantum yield values are measured in the range of 0.12 to 0.17% for a better comparison of the emission properties. Additionally, thermal, and structural properties are investigated to reveal the favorable properties of the selected tellurite glass host. Ultimately, several patterns are designed and constructed by a screen-printing technique using powdered glass to demonstrate its suitability as a multicolor imaging method for anti-counterfeiting applications. The temporal color tuning of upconversion emission via a facile excitation modulation technique in a glass host clearly indicates that the proposed Er3+/Ho3+ co-doped glasses can be potentially applied in the state-of-the-art technologies, especially for anticounterfeiting purposes. © the Owner Societies.
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    Robust CsPbBr3 and CdSe / Dy3++CdSe quantum dot doped glass nanocomposite hybrid coupling as color converter for solid-state lighting applications
    (Elsevier B.V., 2021) Kıbrıslı O.; Erol E.; Çelikbilek Ersundu M.; Ersundu A.E.
    CsPbX3 (X = Br-, Cl-, I-) and IIB-VIA group quantum dots (QDs) exhibit great potential for diverse opto-electronic applications due to their outstanding photoluminescence features. However, poor long-term stability limits their integration into practical applications. Although various surface modification and encapsulation methods have been proposed to increase their durability, desired stability values along with favorable emission properties could not be achieved yet. In this work, controlled crystallization of CsPbBr3 and CdSe QDs are realized separately in a specially tailored silicate glass matrix to obtain quantum dot doped glass nanocomposite (GNC) layers showing typical bright green emission and broadband emission that covers red end of the visible spectrum, respectively. Two alternative white LED devices are constructed as a proof-of-concept by coupling CsPbBr3 doped layer with CdSe and Dy3++CdSe doped layers on top of a blue LED chip to demonstrate excellent color conversion performance and challenging color rendering index values up to 85. CsPbBr3 doped GNC layer exhibits photoluminescence quantum yield (PLQY) up to 40.44%, while PLQY of CdSe doped layer is enhanced up to 18.68% via incorporation of Dy3+ ions. PL properties of GNCs are reversible up to 275 °C and stable after 60 days of immersion in water or under 442 nm laser irradiation (5 W/cm2) up to 30 min. Promising thermal, chemical, and photo stability properties reveal that hybrid coupling of GNCs exhibit high potential to be used as color convertors in solid-state lighting applications. © 2021 Elsevier B.V.
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    Recent progress in lanthanide-doped luminescent glasses for solid-state lighting applications - A review
    (IOP Publishing Ltd, 2021) Erol E.; Vahedigharehchopogh N.; Kibrisli O.; Ersundu M.C.; Ersundu A.E.
    Nowadays, solid-state white light-emitting diodes (wLEDs) have attracted remarkable attention for applications in general lighting, displays and numerous electronical devices due to their eminent efficiency, longer lifetime and higher mechanical durability compared to traditional incandescent and fluorescent lights. In current commercial wLEDs, a combination of Y3Al5O12:Ce3+ yellow phosphor with blue LED chip and epoxy resin is generally used to generate white light. However, there are some considerable frailties mostly originated from phosphor and resin such as, degradation upon heat, and moisture, inhomogeneous spectral distribution, and poor color rendering capability. Therefore, phosphor embedded glass-ceramics have been developed as a promising way to obtain durable solid-state lighting devices. However, in these methods, there is a greater risk of reactions between the phosphor material and the glass host. At this point, lanthanide-doped luminescent glasses have drawn great attention as a new generation phosphor and/or epoxy free white-light-emitting source owing to their favorable properties including high thermal and chemical stability, high transparency, and easy manufacturing process. This review article aims to comprehensively summarize the recent progress in singly (i.e., Dy3+, Eu2+), doubly (i.e., Dy3+/Eu3+, Dy3+/Tm3+, Dy3+/Ce3+, Ce3+/Sm3+, Ce3+/Tb3+) and triply (i.e., Ce3+/Tb3+/Mn2+, Eu3+/Tb3+/Tm3+, Ce3+/Tb3+/Eu3+, Tm3+/Tb3+/Sm3+, Ce3+/Dy3+/Eu3+, Ho3+/Tm3+/Yb3+, Er3+/Tm3+/Yb3+) lanthanide-doped glasses for solid-state lighting applications through down-shifting and up-conversion emissions. Theoretical background including energy transfer mechanisms, glass synthesis methods, radiative and colorimetric properties are given in details. Finally, various effective strategies are highlighted that minimize the critical challenges associated with lanthanides - such as providing energy transfer from quantum dots or nanoparticles to lanthanides, and doping lanthanides in low phonon energy glass - to improve the white light emission of luminescent glasses and broaden their application areas. © 2021 IOP Publishing Ltd.
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    A straightforward approach for high-end anti-counterfeiting applications based on NIR laser-driven lanthanide doped luminescent glasses
    (Royal Society of Chemistry, 2021) Vahedigharehchopogh N.; Kıbrıslı O.; Erol E.; Çelikbilek Ersundu M.; Ersundu A.E.
    The increase in forgery in documents and authentic products has motivated the search for new high-end anti-counterfeiting strategies. Various chameleon-like luminescent materials such as up-conversion nanoparticles or perovskite nanocrystals have drawn attention due to their favorable properties. However, these materials are fabricated through complex processes and often suffer from system instability. In this work a facile and inexpensive approach for color tuning of thermally and chemically stable Ho3+/Tm3+/Yb3+doped tellurite glasses is experimentally demonstrated for the first time. The emission band ratios are successfully manipulated by focusing/defocusing the NIR laser beam irradiating the glass samples. Impressive up-conversion quantum yield values up to 4.56% are obtained along with high lifetime values from ∼100 to 200 microseconds. As proof of concept, a series of anti-counterfeiting patterns are created using the screen-printing method and different emission colors are observed by easily changing the distance between the sample and the laser focal point. The applicability of the presented strategy along with the remarkable properties of the studied lanthanide doped glasses proves the capability of these materials to be used in anti-counterfeiting applications. © The Royal Society of Chemistry 2021.
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    Recyclability of CsPbBr3 quantum dot glass nanocomposites for their long-standing use in white LEDs
    (Royal Society of Chemistry, 2022) Vahedigharehchopogh N.; Erol E.; Kıbrıslı O.; Genç A.; Çelikbilek Ersundu M.; Ersundu A.E.
    The embedding of CsPbBr3 perovskite quantum dots (PQDs) in an inorganic glass matrix not only protects them against chemical, thermal, and photodegradation but also provides an effective strategy to isolate toxic elements such as Pb from the environment for a long period of time. Herein, the recyclability of glass is another important feature that contributes to environmental sustainability. Hence, effective and efficient recycling technologies are needed for the widespread use of PQD glass nanocomposites (GNCs) in many commercial applications. However, studies on the recyclability of CsPbBr3 PQD GNCs have not been conducted so far. Therefore, in this work, we investigate the structural, thermal, optical, and photoluminescence properties of recycled CsPbBr3 PQD GNCs to assess their suitability as long-standing and reusable luminescent materials. For this purpose, the recyclability of GNCs is checked by three repeated melt-quenching and subsequent heat-treatment processes. Although the color emission properties of GNCs under the same heat-treatment conditions show a slight variation after each recycling step, PQD GNCs almost retain their PLQY even after the last recycling step. Ultimately, a prototype white light-emitting diode is constructed by coupling recycled PQD GNCs and a commercial red phosphor on top of a blue LED chip showing high-performance with CIE color coordinates of x = 0.3228, y = 0.3470 and a CCT value of 5920 K. The findings of this work reveal that the recyclability of PQD GNCs holds great promise for a more sustainable technology. © 2022 The Royal Society of Chemistry.
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    Ultra-stable Eu3+/Dy3+ co-doped CsPbBr3 quantum dot glass nanocomposites with tunable luminescence properties for phosphor-free WLED applications
    (Elsevier Ltd, 2022) Erol E.; Vahedigharehchopogh N.; Ekim U.; Uza N.; Çelikbilek Ersundu M.; Ersundu A.E.
    Colloidal CsPbBr3 perovskite quantum dots (PQDs) have substantially improved modern optoelectronic applications, including solid-state lighting, thanks to their highly pure and intense green light emission. However, some drawbacks including lead toxicity, poor stability, and difficulties in emission color tuning hinder their practical applications. Herein, ultra-stable Eu3+/Dy3+ co-doped CsPbBr3 PQD glass nanocomposites (GNCs) with tunable color emissions from green to red and then white are synthesized via melt-quenching followed by heat-treatment method to be used in white light-emitting diodes (WLEDs). Eu3+ and Dy3+ ions are selected to overcome the color tunability obstacle of PQDs and to obtain phosphor-free white light emission with enhanced CRI values. The photoluminescent performance of GNCs is shown to be reversible at elevated temperatures and remains stable even in water. Ultimately, a prototype WLED is constructed by coupling a selected Eu3+/Dy3+ co-doped CsPbBr3 PQD GNC on top of a 400 nm-emitting LED chip to demonstrate its superior optical performance with a color rendering index of 78 and correlated color temperature of 5436 K. The developed GNCs with long-term stability, and excellent tunable luminescent properties may overcome the commercialization barriers of CsPbBr3 PQDs for WLED applications. © 2022 Elsevier B.V.
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    CdSe and CsPbBr3quantum dot Co-doped monolithic glasses as tunable wavelength convertors
    (IOP Publishing Ltd, 2022) Kibrisli O.; Erol E.; Ersundu A.E.; Celikbilek Ersundu M.
    CdSe and CsPbBr3 quantum dots (QDs) are well studied photoluminescent materials due to their extraordinary emission properties. However, their vulnerability against environmental conditions limits their integration into further applications. At this point, glass encapsulation offers promising durability features due to its robust and dense structure. In this study, CdSe and CsPbBr3 QDs are successfully synthesized in the same glass host through the melt-quenching technique followed by a single heat-treatment process. Excitation wavelength dependent photoluminescence properties are investigated and emission color tunability of monolithic glasses from yellow-green to red is demonstrated. Favorable quantum yield values are obtained as 21.78% and 16.63% under 345 and 365 nm excitation wavelengths, respectively. The prepared glasses demonstrate high potential to be used as tunable wavelength convertors for state-of-the-art photonic and opto-electronic applications. © 2021 IOP Publishing Ltd.
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    Color tunable emission from Eu3+and Tm3+co-doped CsPbBr3quantum dot glass nanocomposites
    (Royal Society of Chemistry, 2022) Erol E.; Kibrisli O.; Çelikbilek Ersundu M.; Ersundu A.E.
    Cesium lead bromide (CsPbBr3) quantum dots (QDs) have shown great potential in the field of luminescent materials owing to their superior optical and electrical properties. However, instability and lack of multicolor emissions resulting from the intrinsic nature of CsPbBr3 QDs are still the major challenge for their commercialization. Herein, Eu3+ and Tm3+ co-doped CsPbBr3 QD glass nanocomposites (GNCs) are successfully synthesized via traditional melt-quenching followed by a heat-treatment route to obtain tunable emission in a durable host material. Tm3+ ions are doped to blue-shift the main emission peak of CsPbBr3 QDs, while Eu3+ ions are incorporated to compensate for the red deficiency. Accordingly, a tunable color emission spanning the entire visible spectrum is achieved from GNCs with a fixed composition. The incorporation of Eu3+ and Tm3+ ions promotes the crystallization of CsPbBr3 QDs in the glass host resulting in ∼100% photoluminescence quantum yield (PLQY) using a dilution method. The selected glass host has also been proven to effectively protect CsPbBr3 QDs against chemical, thermal and photo degradation. Interestingly, the selected Eu3+/Tm3+ co-doped CsPbBr3 QD GNC shows warm-white light with a low color temperature of 3692 K without utilizing any commercial phosphors. This indicates that the produced GNCs have the potential to be used as light convertor materials in multi-color LED or warm white LED applications due to their robust stability and extremely pure and tunable emission colors. © 2022 the Owner Societies.
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    Bright white light emission from blue emitting carbon dot-coated Dy3+-doped luminescent glasses
    (Elsevier Ltd, 2022) Özlem B.; Korkmaz U.; Erol E.; Alaş M.Ö.; Meray Z.; Genç Altürk R.; Çelikbilek Ersundu M.; Ersundu A.E.
    Dy3+-doped luminescent glasses have received great attention due to their ability to emit white light at a suitable yellow-to-blue intensity ratio. However, achieving bright white light using single Dy3+-doped glasses remains a challenge due to the hypersensitivity of the emission band at 575 nm — usually resulting in intense yellow emission. In this work, we present a novel approach for compensating for the blue emission deficiency of Dy3+ to produce resin-free white light-emitting diodes (WLEDs) by synthesizing two series of Dy3+-doped glasses from tellurite and silicate systems on which blue-emitting carbon dots (BCDs) are spin-coated. The structural, chemical, optical, and luminescence properties of tellurite and silicate glasses are compared and discussed in detail. White light emissions are obtained upon 365-nm excitation for BCD-coated Dy3+-doped tellurite and silicate glasses with color coordinates of (x = 0.31, y = 0.33) and (x = 0.31, y = 0.34) and correlated color temperatures (CCT) of 5518 K and 5316 K, respectively. BCDs coating increases photoluminescence quantum yield (PLQY) values from 3.10 % to 5.62 % and from 20.81 % to 31.49 % for tellurite and silicate glasses, respectively. Ultimately, the findings in this work show the potential of BCD-coated luminescent glasses with excellent luminescent properties to be considered in solid-state lighting applications. © 2022 Elsevier B.V.
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    The coupling of blue emitting carbon dots with Eu3+/Tb3+ co-doped luminescent glasses for utilization in white light emitting diodes
    (Royal Society of Chemistry, 2023) Korkmaz U.; Özlem B.; Erol E.; Alas M.I.; Genç Altürk R.; Çelikbilek Ersundu M.; Ersundu A.E.
    Lanthanide-doped luminescent glasses have attracted tremendous attention in modern optoelectronic applications, especially for solid-state white light-emitting diodes (WLEDs). Eu3+/Tb3+ co-doped luminescent glasses are well-known to emit intense yellowish-orange light resulting from the energy transfer from green-emitting sensitizer Tb3+ ions to red-emitting activator Eu3+ ions. Obtaining highly efficient blue light from lanthanide ions remains a challenge due to their weak down-converted emission. In this work, we attempt to use the unique characteristics of blue-emitting carbon dots (BCDs), i.e., a broad emission spectrum, ease of synthesis, and high stability, to compensate for this blue light deficiency problem. Correspondingly, a new strategy is proposed by coupling BCDs with Eu3+/Tb3+ co-doped glasses for their potential utilization in WLEDs. Hence, Eu3+/Tb3+ co-doped glasses are prepared in different thicknesses, i.e., 0.8, 1, and 1.5 mm, via the conventional melt-quenching method and subsequently spin-coated with BCDs to achieve adjustable photoluminescence quantum yield (PLQY) values. Ultimately, a proof-of-concept WLED is prepared using a 0.8 mm thick BCD-coated Eu3+/Tb3+ co-doped luminescent glass exhibiting outstanding luminescence performance with a CRI value of 92, a CCT of 4683 K, color coordinates of (x = 0.3299, y = 0.3421), a satisfying PLQY value of 55.58%, and a corresponding LER value of 316 lm W−1 under the excitation of a 375 nm UV LED. BCD-coated Eu3+/Tb3+ co-doped luminescent glasses show excellent stability against photobleaching, temperature variations, and humidity. The findings of this work indicate that the coupling of BCDs with Eu3+/Tb3+ co-doped luminescent glasses holds great potential as a substitute for traditional solid-state lighting sources. © 2023 The Royal Society of Chemistry.