Ultrastable Luminescent Organic–Inorganic Perovskite Quantum Dots via Surface Engineering: Coordination of Methylammonium Bromide and Covalent Silica Encapsulation

Abstract

Encapsulation of luminescent perovskite quantum dots (QDs) into a solid matrix has been approved to be an efficient way to improve their stability. In this work, we reported a green encapsulation method to produce ultrastable CH 3 NH 3 PbBr 3 QDs incorporated into the SiO 2 matrix. Specifically, fresh-prepared CH 3 NH 3 PbBr 3 QDs were covalently embedded into silica by an aqueous sol−gel method assisted with CH 3 NH 3 Br, which not only effectively inhibited the water-driven degradation of QDs through surface coordination, but also strongly stabilized the QDs in solid powder via concentration gradient. As far as we know, this silica encapsulation of perovskite QDs in aqueous environments is reported for the first time. Luminescent properties of perovskite QDs during the course of gelation as well as in resulting composite powder were investigated using steady-state and time-resolved spectroscopies, and a 2 wt % QD-doped sample treated with 11.5 mM of CH 3 NH 3 Br was demonstrated to be the optimal phosphor. The green-emissive phosphor had a PLQY of 60.3% and a full width at half maxima of ∼25 nm, exhibiting ultrahigh stability tested by cycle heating (120 °C), continuous heating (80 °C, 60 h), and light irradiation (450 nm light, 350 h). The phosphor was readily blended with polymers and applied as a color-converting layer on blue light-emitting diodes.

Recent Progress on Synthesis, Characterization, and Applications of Metal Halide Perovskites@Metal Oxide

“…In 1845, the French chemist J. J. Ebelmen mixed SiCl 4 with ethanol to form tetraethoxysilane (TEOS) and a gel was formed during hydrolyzing in wet air. [73] Currently, this method is mostly used to fabricate the shell coating with SiO 2 , [74][75][76][77][78][79][80][81][82][83][84][85][86] TiO 2 , [84,87,88] ZrO 2 , [70] Al 2 O 3 /SiO 2 , [69] SiO 2 /ZrO 2 [89] around the surface of the MHPs core.…”

“…Further works have also confirmed that MHPs@MO x feature enhanced photostabilities than the pristine MHP counterparts. [37,75,77,125,140] For instance, the CsPbBr 3 NC and CsPbBr 3 NC/MO 2 (M = Si, Ti, Sn) films were fabricated on the fluorine doped tin oxide substrates through a centrifugally cast process. [84] These films were exposed to the 365 nm UV light to test the photostability.…”

“…In average, SiO 2 coatings increases the temperature threshold up to 90-100 °C to reach 50% of the initial PL intensity and stabilities of 15 h at 60 °C. [75,80,134] The thermal quenching problem is still very severe for the MHPs even though the above significant enhancements have been achieved, as the widely adopted silica encapsulation can only help reduce the problems caused by the thermal induced aggregation. Traps caused by the thermal induced halogen vacancies are also responsible for the thermal quenching.…”

“…MHPs@SiO 2 composites, which show excellent environmental stability, high PLQYs, good spectral tunability, narrow FWHM, are ideal candidates for the application in the pc-WLEDs. [74,75] Table 4 is the summary of the device performance for MHPs@MO x based pc-WLEDs. The representative ways can be used to realize the MHPs@SiO 2 based pc-WLEDs are: i) combining the blue LED chip, MHPs@SiO 2 with another MHP with different colors (first type), [35,79,93,130,134] ii) combining the blue LED chip, the MHPs@SiO 2 with other kind of luminescent materials, such as the traditional inorganic CdSe QDs or commercial red phosphors, like KSF, Sr 2 Si 5 N 8 :Eu 2+ , CaAlSiN 3 :Eu 2+ (second type); [70,75,76,101,135,140] iii) achieving the pc-WLEDs by using a UV LED chip in combination with yellow and green or blue phosphor at controllable wavelength (third type).…”

Room-Temperature Synthesis of Air-Stable Near-Infrared Emission in FAPbI3 Nanoparticles Embedded in Silica

“…Hu et al, reported the silica-coated process to encapsulate CdSe/ZnS QDs in 2009 [ 31 ], but silica-coated CsPbX 3 (X = Cl, Br and I) PNPs compounds were fabricated until 2016 [ 32 , 33 ]. Subsequently, APTES [ 34 , 35 , 36 ], tetraethylorthosilicate (TEOS), and Tetramethoxysilane (TMOS) were utilized to form silica-coated CsPbX 3 (X = Cl, Br and I) PNPs.…”