Preparation of highly luminescent BaSO₄ protected CdTe quantum dots as conversion materials for excellent color-rendering white LEDs

Abstract

The incorporation of colloidal CdTe quantum dots into an inorganic matrix, BaSO 4 , through a handy and rapid co-precipitation method is demonstrated for the first time. Owing to the protection of the BaSO 4 matrix, the resulting composites show stronger luminescence, longer fluorescent lifetime, and higher photo-and thermal stability as well as being more anti-acid compared to the parental CdTe QDs.Moreover, the composites hold several advantages for industrial applications. White light-emitting diodes (WLEDs) utilizing the composites as a red color conversion layer are fabricated, and produce bright white light with high color-rendering properties including a CIE coordinate of (0.34, 0.33), an R a of 88, and a T c of 5112 K at 20 mA, suggesting their great potential application in a solid-state lighting system with high color-rendering properties.

Stability of Quantum Dots, Quantum Dot Films, and Quantum Dot Light‐Emitting Diodes for Display Applications

“…Overcoating enhances QD stability by protecting the QDs from air, moisture, heat, and high energy light, as summarized in Table , but the overcoating should be tailored to avoid quantum yield reduction and wavelength change . Inorganic overcoating to enhance photostability, acid stability, and thermal stability has been achieved using air‐stable inorganic salts, such as BaSO 4 , and KCl, or metal–organic complexes . Overcoating by inorganic salts is reported to cause the redshift of the emission wavelength due to aggregation.…”

Rapid green manufacture of high yield CdTe@Ca(OH)2 nanocrystals and their performance on WLED

“…We investigated PL properties of CdTe QDs solution and the CdTe@Ca(OH) 2 nanocrystals. As shown in Figure a, the emission wavelength of CdTe@Ca(OH) 2 exists nearly 7 nm red‐shift comparing with that of CdTe QDs, which can be explained by changes of the dielectric constant of the surrounding media as well as by reabsorption of the emission from small nanocrystals by larger ones . Figure b is PL spectra of CdTe@Ca(OH) 2 under different concentrations of Ca(OH) 2 .…”

“…The PL lifetime appears longer as the increasing of the concentration of Ca(OH) 2 . That result suggests that there exists the enhanced surface passivation effect when the concentrations of Ca(OH) 2 increase from 0 to 1.0 M, preventing aggregation of QDs, further causing the prolonging of the PL lifetime …”

“…To solve it, much effort has been developed by designing core/shell structural QDs, such as CdTe/ZnS, CdTe/ZnSe, or CdTe/ZnTe core/shell QDs and the like . Another solution is that some approaches adopted stable inorganic compounds to encapsulate QDs, further enhancing their stability of as‐prepared QDs . Although the progresses have been made, the as‐generated toxic heavy metal ions waste water still exists during the producing process, along with harsh separation of QDs powder, limiting their extensive industrialization of QDs.…”

Incorporation of Nanoparticles into Inorganic Salt Crystals (review)

“…Китайськими вченими досліджено впровадження квантових точок CdTe в матрицю BaSO 4 [28]. Композитний порошок отримували шляхом розчинення 0,426 г натрій сульфату у 30 мл розчину наночастинок з подальшим швидким додаванням 5 мл розчину з 0,728 г барій хлориду.…”