Browsing by Subject "Perovskite nanocrystals"

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Open Access
Ag@SiO2-embedded InGaN/GaN nanorod array white light-emitting diode with perovskite nanocrystal films
(Elsevier, 2021-10-28) Shin, Do-Y.; Kim, T.; Akyüz, Özgün; Demir, Hilmi Volkan; Lee, In-H.
White light-emitting diodes (LEDs) are great candidates for general lighting. Phosphors have commonly been used for the color conversion layers of white LEDs; however, they backscatter more than half of the down-converted light, which is lost within the device, thus degrading the overall performance. In this study, we propose and demonstrate white LEDs with improved efficiency enabled by the intimate integration of Ag@SiO2-supported blue InGaN/GaN nanorod LEDs together with green- and red-emitting perovskite nanocrystal (PNC) films as color conversion layers. The photoluminescence (PL) intensity of the blue LEDs (BLEDs) was significantly enhanced owing to the localized surface plasmon (LSP) effect of Ag@SiO2 nanoparticles. In addition, the perovskite PL intensity was improved by the high-power BLED backlight. The resulting PL intensity of the Ag@SiO2 nanoparticle-embedded nanorod white LED was 62% greater than that of a planar white LED.
Open Access
Multiplexed patterning of cesium lead halide perovskite nanocrystals by additive jet printing for efficient white light generation
(Elsevier, 2020-08-12) Altıntaş, Y.; Torun, İ.; Yazıcı, A. F.; Beşkazak, E.; Erdem, T.; Önses, M. Serdar
Inorganic perovskite nanocrystals (PNCs) offer the ability to precisely but also flexibly control the peak emission wavelength while also possessing narrow-band emission spectra and high quantum yields. Owing to these features, PNCs have been already employed as color converters on LEDs. Nevertheless, the anion exchange reactions that prevent the blending of perovskites of different colors remain as an important bottleneck. As a remedy to this issue, here we employ additive jet printing to form separated stripes of these nanocrystals. Within this framework, we first present the synthesis of CsPbBr3 and CsPbBrxI3−x nanocrystals spanning the whole visible regime and optimize the cleaning procedure to obtain PNCs possessing photoluminescence quantum yields as high as 91% and emission linewidths as narrow as 15 nm, making them suitable for high quality white light generation. Next, we employ electrohydrodynamic jet printing to form closely spaced stripes of PNCs of various colors and integrated these films with a blue LED to create a white LED. Our proof-of-concept LED achieves high photometric performance as it possesses a color rendering index of 91.3, luminous efficacy of optical radiation > 300 lm/Wopt, and correlated color temperature of ca. 7000 K. We believe that additive jet printing technique will pave the way for a ubiquitous use of these PNCs in light-emitting devices in the near future.
Open Access
Natural wax-stabilized perovskite nanocrystals as pen-on-paper inks and doughs
(American Chemical Society, 2022-05-27) Karabel Ocal, S.; Kiremitler, N. B.; Yazici, A. F.; Çelik, N.; Önses, M. Serdar; Mutlugün, Evren
Perovskite nanocrystals (PNCs) are emerging luminescent materials for a wide range of technological applications. The broad adaptation of PNCs will be greatly improved by addressing their intrinsically low stability and developing processes for their assembly into 2D and 3D structures using facile approaches. Inspired by the mechanism of natural protection of leaves, this paper proposes natural carnauba wax (CW) as an encapsulation material for PNCs. The synthesis of PNCs is performed in the presence of CW, which is derived from the leaves of Copernicia prunifera palm. CW acts as a solvent and replaces the commonly used octadecene in the preparation of PNCs. The facile synthesis in CW results in PNCs with greatly improved thermal, water, and air stability. Furthermore, the thermal and mechanical properties make PNC-Wax a highly suitable solid ink for versatile processing of these materials into 2D and 3D architectures. PNC-Wax can be printed via a pen-on-paper approach by heating at modest temperatures. The rapid plasticization of PNC-Wax by mechanical agitation enables hand-shaping of the material in a manner similar to playdoughs, which would possibly enable the versatile use of this material for various applications. © 2022 American Chemical Society. All rights reserved.