Super-Hydrophobic Cesium Lead Halide Perovskite Quantum Dot-Polymer Composites with High Stability and Luminescent Efficiencyfor Wide Color Gamut White Light-Emitting DiodesTongtong Xuan,†,⊥ Junjian Huang,†,⊥ Huan Liu,∥ Sunqi Lou,† Luyu Cao,† Weijiang Gan,†

Ru-Shi Liu,*,‡,§ and Jing Wang*,†

†Ministry of Education Key Laboratory of Bioinorganic and State Key Laboratory of Optoelectronic Materials and Technologies,School of Chemistry, School of Materials Science and Engineering, Sun Yat-Sen University, Guangzhou, Guangdong 510275, China‡Department of Chemistry, National Taiwan University, Taipei 106, Taiwan§Department of Mechanical Engineering and Graduate Institute of Manufacturing Technology, National Taipei University ofTechnology, Taipei 106, Taiwan∥Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry, BeihangUniversity, Beijing 100191, China

*S Supporting Information

ABSTRACT: We present a novel composite strategy toenhance the stability of water-sensitive CsPbBr3 quantum dots(QDs) by embedding the QDs into the super-hydrophobicporous organic polymer frameworks (CPB@SHFW). TheCPB@SHFW composites not only preserve a high photo-luminescence quantum yield (PLQY ≈ 60%) and narrowband emission (full width at half-maximum ≈ 16 nm) but alsoinherit the outstanding water-resistant property of SHFW toprotect the QDs from hydrolytic degradation. The PLQY ofthe composites was maintained at 91% (PLQY ≈ 54.3%) ofthe initial one (PLQY ≈ 60%) after being immersed in waterfor 31 days. Even after being immersed in water for 6 months,the CPB@SHFW composites still retain a bright greenemission. In addition, super-hydrophobic perovskite QD-polymer composites (IPQDs@SHFW) with tunable and bright emission were prepared by using suitable halide salts. A whitelight-emitting diode (WLED) device was prepared by combining green-emitting CPB@SHFW composites and red-emittingK2SiF6:Mn4+ phosphors with a blue LED chip. The device exhibits a high luminous efficiency of 50 lm/W and a wide colorgamut (127% of the National Television System Committee and 95% Rec. 2020). This work provides an alternative approach tosolve the challenging stability issue of perovskite QDs; therefore, it has a positive implication for their practical application inliquid crystal display backlights.

■ INTRODUCTION

All inorganic lead halide perovskite quantum dots (IPQDs),CsPbX3 (X = Cl, Br, I), have been attracting increasingattention for their excellent optical properties, such as tunableemission wavelength, high photoluminescence quantum yield(PLQY), narrow full width at half maximum (fwhm), and highdefect tolerance.1−4 Therefore, the IPQDs have potentialapplication in solar cells, light-emitting diodes (LEDs), andlasers.5−9 Unfortunately, the IPQDs suffer from poor stabilitybecause of the hydrolytic degradation, which limits theirpractical applications.6,10−14

Up to now, great efforts worldwide have been made to facethe moisture-sensitive problem of the perovskite QDs. Amongprevious reports, the water-resistant organic ligands, polymers,or silicon dioxide were coated on the surface of the perovskite

QDs as a protecting layer by ligand exchanging orencapsulation to enhance water stability, as shown in FigureS1.11,12,15−26 For example, Huang et al. coated polyhedraloligomeric silsesquioxane on the surface of CsPbX3 QDs withenhanced hydrolytic resistance. Lin et al. reported theencapsulation of the perovskite QDs in polystyrene withbright emission and enhanced the water-resistant property.27

Moreover, atomic layer deposition for the growth of theamorphous alumina matrix on CsPbBr3 QDs was proved toexceptionally improve stability toward exposure to air and evenupon immersion in water for a short time.17 The main idea of

Received: November 1, 2018Revised: January 17, 2019Published: January 17, 2019

Article

pubs.acs.org/cmCite This: Chem. Mater. 2019, 31, 1042−1047

© 2019 American Chemical Society 1042 DOI: 10.1021/acs.chemmater.8b04596Chem. Mater. 2019, 31, 1042−1047

Dow

nloa

ded

via

NA

TL

TA

IWA

N U

NIV

on

Mar

ch 2

9, 2

019

at 0

6:43

:11

(UT

C).

Se

e ht

tps:

//pub

s.ac

s.or

g/sh

arin

ggui

delin

es f

or o

ptio

ns o

n ho

w to

legi

timat

ely

shar

e pu

blis

hed

artic

les.

the previous work is focused on the water-resistance of organicor inorganic coating layers themselves but not their micro-structure (Figure S1). Instead, we proposed a new super-hydrophobic structure concept to enhance the water stabilityof perovskite QDs, which is rarely reported in previous work.Super-hydrophobic materials have been extensively applied

to a broad range of fields because of the unique water-repellentproperty of water contact angles (CAs) greater than 150°.28−30

The super-hydrophobic surfaces generally arise from theirhierarchical pore structures from nanometer to micrometerscales. Recently, porous organic polymers (POPs) have beendeveloped as a new platform to construct hierarchical porousframeworks in the presence of the suitable pore-making agent,which results in a super-hydrophobic property.31,32 Because ofthe super-hydrophobicity and the hierarchical porous structureof the POPs, we envision whether the moisture-sensitiveIPQDs can be absorbed into the POPs forming composites.The composites not only preserve the excellent opticalproperties of the IPQDs but also inherit the outstandingsuper-hydrophobicity of the POPs to resist hydrolyticdegradation.Here, we report a novel strategy (Figure 1) to enhance a

water-resistance property of the CsPbBr3 QDs by absorbing

the QDs into super-hydrophobic POP frameworks (SHFW)and forming super-hydrophobic composites (CPB@SHFW).The composites exhibit excellent optical property andsurprising water-resistant property. Divinylbenzene (DVB),ethyl acetate, and azodiisobutyronitrile were chosen asmonomers, pore-making agent, and initiator for preparationof SHFW with a pore size of approximately 10−100 nm,respectively. Therefore, the CsPbBr3 QDs can be easilyadsorbed into the pores of the SHFW forming CPB@SHFWcomposites. On the basis of these stages, super-hydrophobicperovskite composites (IPQDs@SHFW) with tunable emis-sion can be simply obtained by using suitable halide salts. Thecomposites not only exhibit bright emission and high colorpurity but also present a good water-resistant property evenwhen being immersed in water for 6 months. These indicatethey have great potential applications in white light-emittingdiodes (WLEDs) for backlight display.

■ RESULTS AND DISCUSSIONThe SHFW was synthesized by a simple solvothermalmethod,33 and the details are described in the Supporting

Information. It should be noted that the SHFW was washed bychloroform to remove unreacted reagents, which is a vitalprocedure to retain its super-hydrophobicity in high-humidityatmospheres. As shown in Figure S2, the peaks marked by thesolid line at around 1635 and 3085 cm−1 in the infraredabsorption spectra were attributed to the CC bonds andstretching vibrations of C−H of DVB, respectively. Theirrelative intensity distinctively weakened after the polymer-ization process, which indicates the success of this cross-linkingreaction. Table S1 shows the nitrogen sorption isotherms ofthe SHFW. The SHFW exhibits a large Brunauer−Emmett−Teller (BET)-specific surface area (724.3 m2 g−1), a large porevolume (1.8 cm3 g−1), as well as large pores (10−100 nm)distribution (Figure S3). As shown in Figures S4 and S5a,b, themorphology of the SHFW was characterized by usingtransmission electronic microscopy (TEM) and scanningelectron microscopy (SEM), which further confirms theirhierarchical porous structure. Additionally, the super-hydro-phobicity was verified by the drop shape analyzer with a waterCA approximately equal to 150° (Figure S4c). The SHFW notonly has the suitable hierarchical porous structures but alsoexhibits the excellent water-resistant property. Therefore, weexpected it was appropriate for the SHFW to absorb suitableIPQDs to enhance their water stability and retain theirexcellent optical property.Green-emitting CsPbBr3 QDs were synthesized by a

traditional hot-injection method.34 As shown in Figure S6,the QDs exhibit a cubic shape with an average particle size of18 nm, which was smaller than the pores of the SHFW. Thus,it was suitable for the absorption into the SHFW. Figure 2ashows the schematic of CPB@SHFW composites. TheCsPbBr3 QDs were absorbed into the surface pores of theSHFW and gradually moved to the inside pores of the SHFWforming CPB@SHFW composites. The X-ray diffraction(XRD) patterns of SHFW and CPB@SHFW are shown inFigure 2b, which indicates the CsPbBr3 QDs were successfullycomposited with the SHFW. To further confirm the CsPbBr3QDs absorbed in SHFW, SEM and TEM were used to observetheir morphology and structures. As seen from the SEMimages (Figures 2d and S5c,d), the CPB@SHFW compositesshow a hierarchical porous structure, which is similar to that ofthe pure SHFW (Figures S4b and S5a,b).33,35 The TEM image(Figure 2e) of the composites with the light and shade contrastshows that the QDs are mainly distributed in the SHFW. Asshown in Figure S7a, the high-angle annular dark field scanningtransmission electron microscopy image shows that the heavierelements (Pb) were completely wrapped by the carbon of theSHFW. The EDS mapping image (Figure S7c−f) furtherdemonstrates that there is good elemental distribution of Cs,Pb, and Br. Meanwhile, the high-resolution TEM (HR-TEM)image of the embedded QDs (Figure 2e inset) shows thelattice spacing of 0.29 nm, which corresponds to the (200)plane of the cubic-phase CsPbBr3. Combined with these resultsand analyses, we can safely conclude that the CsPbBr3 QDsabsorbed into SHFW forming CPB@SHFW composites. Inaddition, the further BET, optical, and water stabilitymeasurements indirectly confirm the good distribution ofCsPbBr3 QDs in the framework of the SHFW as discussedbelow.To investigate the surface pore structure of CPB@SHFW

composites, the nitrogen sorption isotherms were used toverify their hierarchical porosity. The nitrogen absorption/desorption isotherm patterns of SHFW and CPB@SHFW

Figure 1. Schematic illustration for preparation of CPB@SHFWcomposites.

Chemistry of Materials Article

DOI: 10.1021/acs.chemmater.8b04596Chem. Mater. 2019, 31, 1042−1047

1043

(Figure 2c) both behaved as a typical H4 hysteresis loop,which could be refereed to their hierarchical porosity. A slowincreasing in the absorption amounts in the relative pressurerange of 0.4−0.8 indicates the presence of mesopores, and adramatic increasing at high relative pressure (>0.9) verifies the

presence of large pores. Table S1 and Figure S3 reveal thatalthough the BET-specific surface area and aperture base onthe Barrett−Joyner−Halenda measurement decreases from724 to 303 m2 g−1, and 75 to 51 nm, respectively, because ofthe absorption of CsPbBr3 QDs in the pores of SHFW, their

Figure 2. (a) Schematic of CPB@SHFW composites. The XRD patterns (b) and BET curves (c) of SHFW and CPB@SHFW composites,respectively. (d) SEM image of CPB@SHFW composites. The inset in the top right corner is the image of the composites under 365 nm UV lightand the bottom right corner is the image of a water droplet on their surface. (e) TEM image of the composites. The inset in the top right corner isthe HR-TEM images. (f) PL spectra of SHFW, CsPbBr3 QDs, and CPB@SHFW composites, respectively.

Figure 3. (a) PLQY of CPB@SHFW composite powders as a function of time in water (inset: the CA images before and after being immersed inwater for 31 days). (b) Photographs of CPB@SHFW composite powders immersed in water for 3 months and 6 months under white light and 365nm UV light, respectively. (c) Photographs of blue-, green-, and red-emitting IPQDs@SHFW composite powders, and the images of water dropson the composite films under white light and 365 nm UV light, respectively. (d) PL spectra of the IPQDs@SHFW composite powders.

Chemistry of Materials Article

DOI: 10.1021/acs.chemmater.8b04596Chem. Mater. 2019, 31, 1042−1047

1044

porosity was well retained after the composite procedure. TheCPB@SHFW composites exhibit pore size distribution from10 to 100 nm with a main pore diameter of 51 nm, which issmaller than the critical bore diameter (100 nm) of the super-hydrophobic structure (more details in the SupportingInformation).30,36 This indicates that the CPB@SHFWcomposites may inherit the super-hydrophobicity property ofthe pure SHFW. The super-hydrophobicity property of theCPB@SHFW composites was further verified by the dropshape analyzer with a water CA of 150° (the inset bottom rightcorner of Figure 2d), which is equal to that of the pure SHFW(Figure S4c). These show that our prepared CBP@SHFWcomposites retain the super-hydrophobicity property of theSHFW. In addition, the composites exhibit the super-hydrophobicity property even at a high temperature (FigureS8).We further investigated the photoluminescent property of

the CPB@SHFW composites. As-prepared sponge-like CPB@SHFW composite powders exhibit bright green emission underexcitation of 365 nm UV light (the inset top right corner ofFigure 2d). The PL spectra of SHFW, CsPbBr3 QDs, andCPB@SHFW are shown in Figure 2f. The SHFW shows noemission in the range 480−580 nm. After centrifugalseparation, the pure CsPbBr3 QD powders exhibit a muchweaker green emission with the PLQY of almost about zeroeven though the PLQY of the CsPbBr3 QD solution was highup to about 80%. Very interestingly, the CPB@SHFW showsthe standard spectra of CsPbBr3 QDs at 518 nm with an fwhmof 16 nm and a high PLQY of about 60% (Figure S9), whichstrongly suggests that the CsPbBr3 QDs have good distributionin the framework of the SHFW.23,37 Most probably, more thanone CsPbBr3 QD is distributed inside one pore of the SHFWbecause the size of the pores of CPB@SHFW is about ∼75nm, larger than the 18 nm of one CsPbBr3 QD. To furtherunderstand the high PLQY of the CPB@SHFW composites,we investigated the lifetime change of the CsPbBr3 before andafter absorbing into the SHFW. Figure S10 shows the PL decaycurves of the CsPbBr3 QDs and CPB@SHFW composites,which were fitted by a two-exponential function (Table S2).The corresponding average lifetimes were 7.9 and 12.8 ns,respectively. The increased lifetime illustrates that the CsPbBr3QDs embedded into the SHFW do not trigger morenonradiative decay and the generated excitons tend torecombine with radiative path, which coincides well with thehigh PLQY.17,38

Although as-prepared CPB@SHFW composite powdersexhibit the super-hydrophobicity property and bright emission,the water stability is still unclear. To evaluate the water stabilityof the CPB@SHFW composites, the composites were directlyimmersed in water (the experimental details are described inthe Supporting Information). Interestingly, when the compo-sites were immersed into the water without vigorous vibrating,they immediately floated on the surface of the water with aclear boundary (Figure 3b) because of the super-hydro-phobicity property. The PLQY of the composites wasmaintained at 91% (PLQY ≈ 54.3%) of the initial one(PLQY ≈ 60%) after being immersed in water for 31 days asshown in Figure 3a. Moreover, the composites still appearstrongly emissive after being immersed in water for 6 months(Figure 3b). It should be mentioned that the CA of thecomposites is still maintained at 150° after being immersed inwater for 30 days. These illustrate that the CsPbBr3 QDs wereindeed absorbed into the SHFW forming CPB@SHFW

composites, which exhibits excellent water stability resultingfrom the super-hydrophobicity property of the composites.The super-hydrophobic structure can repel water away fromthe CsPbBr3 QDs to avoid hydrolytic degradation. We furtherinvestigated the PL stability of CsPbBr3 QDs and the CPB@SHFW composites under blue light radiation (λpeak = 455 nm,6 W). As shown in Figure S11, after being radiated under bluelight for 24 h, the PL intensity of the composites retains 58.6%of the initial one, which is much higher than that of the pureCsPbBr3 QDs (24.6%). Probably, the existence of the SHFWframework slows down the decomposition of the embeddedCsPbBr3 QDs, which is similar to that of SiO2 and Al2O3.

17,39

In addition, the blue-emitting CsPbCl1.5Br1.5@SHFW andred-emitting CsPbBr1.2I1.8@SHFW composite powders wereprepared by a method similar to the one for the CPB@SHFW.Figure 3c shows the photographs of the blue-, green-, and red-emitting composite powders under daylight and 365 nm UVlight and the water drops on their films under 365 nm UVlight. The corresponding PL spectra are shown in Figure 3dand centered at 454, 518, and 648 nm with the fwhm of 22, 16,and 35 nm, respectively. As shown in Figure S12, the red,green, and blue emitting (RGB) perovskite QD powdersexhibit water CA of 110°, 102°, and 109°, respectively, whichindicates that the pure perovskite QDs show a hydrophobicproperty because of the surface organic ligands, such as oleicacid and oleylamine. Comparatively, the water CA of IPQD@SHFW (Figure S13) is greatly larger than that of pure IPQDs,suggesting that the IPQD@SHFW exhibits more superhydrophobic performance than pure IPQDs. Therefore, as-prepared IPQDs@SHFW composites have a long-time-stablesuper-hydrophobic property and high water stability. Inparticular, the PLQY of CsPbI3@SHFW composites remainsat 65% of the initial PLQY after being immersed in water withvigorous vibrating for 9 days (Figure S14), which illustratesthat as-prepared CsPbI3@SHFW composites display greatlyenhanced water stability when compared with the pure CsPbI3QDs.40,41

Compared with the previously reported CsPbBr3−polymercomposites (Table S3),15,16,26,27,42 our prepared green-emitting CPB@SHFW composite powders display a relativelyhigh PLQY, high color purity, and excellent water stability,which makes them promising for use as green phosphors inwide color gamut display devices. A WLED was fabricated byencapsulating a mixture of green-emitting CPB@SHFWcomposite powders, red-emitting K2SiF6:Mn4+ (KSF) phos-phors, and silicone resin onto a blue InGaN LED chip (λpeak =447 nm). As shown in the inset of Figure 4a, the WLED at adriving current of 20 mA generated white emission with a highluminous efficiency of 50 lm/W, and a CommissionInternationale de L’Eclairage (CIE) chromaticity coordinateof (0.329, 0.305) without optimizing the structure of thedevice, which shows better performance than that of theCsPbBr3 QDs, KSF-based WLED (Table S4). The correspond-ing electroluminescence (EL) spectrum (Figure 4a) obviouslyconsists of three emission bands centered at 447, 525, and 630nm, which belong to the blue LED chip, CPB@SHFWcomposites, and KSF phosphors, respectively. As shown inFigure 4b, the chromaticity coordinates of RGB were (0.0.155,0.019), (0.143, 0.763), and (0.691, 0.309), generating atriangle area on the CIE 1931 chromaticity diagram, which wascalculated as 127% of the National Television SystemCommittee (NTSC) space and 95% of Rec. 2020 spaceapproximately. This result was much better than that of the

Chemistry of Materials Article

DOI: 10.1021/acs.chemmater.8b04596Chem. Mater. 2019, 31, 1042−1047

1045

commercial green phosphor-based (β-SiAlON:Eu2+) and KSFphosphor-based WLED, whose NTSC space was merely89%.22 These indicate as-prepared CPB@SHFW compositepowders have great potential as green phosphors for LCDdisplay devices.Besides, the CPB@SHFW composites were demonstrated as

water-resistant ink in the field of fluorescent anti-counter-feiting. It is obviously seen in Figure S15 and Video S2 that the“SYSU” characters written by either the CsPbBr3 QDs or theCPB@SHFW show bright green fluorescence. Unfortunately,after being immersed in water for about 40 min, the CsPbBr3-based “SYSU” exhibits no fluorescence signal. On the contrary,the CPB@SHFW composite-based “SYSU” still retains brightgreen emission under 365 nm UV light after even beingimmersed in water for about 20 h. These indicate that ourprepared CPB@SHFW composite-based fluorescent ink showshigh water stability and has potential application in water-resistant fluorescent ink in the field of fluorescent anti-counterfeiting.

■ CONCLUSIONSIn summary, we present a simple process that enables theCsPbBr3 QDs embedded in the super-hydrophobic frameworkforming CPB@SHFW composites. The composites not onlyexhibit bright emission with narrow-band emission (fwhm = 16nm) and a high PLQY up to 60% but also display super waterstability because of the super-hydrophobicity. The compositesstill show bright green emission even after being immersed inwater for 6 months. Meanwhile, super-hydrophobic blue-,green-, and red-emitting IPQDs@SHFW composite powderswere prepared with excellent optical properties and super-hydrophobicity by using suitable halide salts. Moreover, aWLED device was successfully fabricated based on green-emitting CPB@SHFW composite powders, red-emitting KSFphosphors, and a blue LED chip. The device exhibits a highluminous efficiency of 50 lm/W and a wide color gamut (127%of NTSC, 95% of Rec. 2020). We believe the employment ofsuper-hydrophobic framework to enhance the water stabilityand retain the excellent optical properties of perovskite QDswill energetically facilitate their practical application.

■ ASSOCIATED CONTENT*S Supporting InformationThe Supporting Information is available free of charge on theACS Publications website at DOI: 10.1021/acs.chemma-ter.8b04596.

Experimental details and characterizations (BET, CA,TEM, SEM, PL decays, and PL stability of the SHFWand composites) (PDF)Video S1 shows the water stability instructions of theCPB@SHFW composites (MPG)Video S2 shows the the "SYSU" characters written byeither the CsPbBr3 QDs or the CPB@SHFW under 365nm UV light after being immersed in water for differenttime (MPG)

■ AUTHOR INFORMATIONCorresponding Authors*E-mail: rsliu@ntu.edu.tw (R.-S.L.).*E-mail: ceswj@mail.sysu.edu.cn (J.W.).ORCIDTongtong Xuan: 0000-0002-9176-7826Huan Liu: 0000-0001-9009-7122Ru-Shi Liu: 0000-0002-1291-9052Jing Wang: 0000-0002-1246-991XAuthor Contributions⊥T.X. and J.H. contributed equally.NotesThe authors declare no competing financial interest.

■ ACKNOWLEDGMENTSThis work was financially supported by the NSFCs (51702373,51772336, and 51572302), National Key R&D Program ofChina (2018YFB0406800 and 2018YFB0406801), the “973”programs (2014CB643801), Guangdong Provincial Science &Technology Project (2015B090926011, 2017A050501008, and2013B090800019), Teamwork Projects of Guangdong NaturalScience Foundation (S2013030012842), and GuangzhouScience & Technology Project (201807010104). This workwas also supported by the Ministry of Science and Technologyof Taiwan (contract no. MOST 107-2113-M-002-008-MY3).

■ REFERENCES(1) Huang, H.; Bodnarchuk, M. I.; Kershaw, S. V.; Kovalenko, M. V.;Rogach, A. L. Lead Halide Perovskite Nanocrystals in the ResearchSpotlight: Stability and Defect Tolerance. ACS Energy Lett. 2017, 2,2071−2083.(2) Akkerman, Q. A.; Raino,̀ G.; Kovalenko, M. V.; Manna, L.Genesis, challenges and opportunities for colloidal lead halideperovskite nanocrystals. Nat. Mater. 2018, 17, 394−405.(3) Kovalenko, M. V.; Protesescu, L.; Bodnarchuk, M. I. Propertiesand Potential Optoelectronic Applications of Lead Halide PerovskiteNanocrystals. Science 2017, 358, 745−750.(4) Pan, G.; Bai, X.; Yang, D.; Chen, X.; Jing, P.; Qu, S.; Zhang, L.;Zhou, D.; Zhu, J.; Xu, W.; Dong, B.; Song, H. Doping Lanthanide intoPerovskite Nanocrystals: Highly Improved and Expanded OpticalProperties. Nano Lett. 2017, 17, 8005−8011.(5) Zhang, M.; Hu, B.; Meng, L.; Bian, R.; Wang, S.; Wang, Y.; Liu,H.; Jiang, L. Ultrasmooth Quantum Dot Micropatterns by a FacileControllable Liquid-Transfer Approach: Low-Cost Fabrication ofHigh-Performance QLED. J. Am. Chem. Soc. 2018, 140, 8690−8695.(6) Wang, H.-C.; Bao, Z.; Tsai, H.-Y.; Tang, A.-C.; Liu, R.-S.Perovskite Quantum Dots and Their Application in Light-EmittingDiodes. Small 2018, 14, 1702433.(7) Chen, X.; Li, D.; Pan, G.; Zhou, D.; Xu, W.; Zhu, J.; Wang, H.;Chen, C.; Song, H. All-inorganic perovskite quantum dot/TiO2inverse opal electrode platform: stable and efficient photoelectro-chemical sensing of dopamine under visible irradiation. Nanoscale2018, 10, 10505−10513.

Figure 4. (a) EL spectrum of a WLED based on CPB@SHFWcomposites, KSF phosphors, and a blue LED chip (inset: thephotograph of the WLED operated at 20 mA). (b) Color coordinateand the gamut of the WLED.

Chemistry of Materials Article

DOI: 10.1021/acs.chemmater.8b04596Chem. Mater. 2019, 31, 1042−1047

1046

(8) Pan, G.; Bai, X.; Xu, W.; Chen, X.; Zhou, D.; Zhu, J.; Shao, H.;Zhai, Y.; Dong, B.; Xu, L.; Song, H. Impurity Ions Codoped CesiumLead Halide Perovskite Nanocrystals with Bright White LightEmission toward Ultraviolet-White Light-Emitting Diode. ACS Appl.Mater. Interfaces 2018, 10, 39040−39048.(9) Bi, C.; Wang, S.; Wen, W.; Yuan, J.; Cao, G.; Tian, J. Room-Temperature Construction of Mixed-Halide Perovskite QuantumDots with High Photoluminescence Quantum Yield. J. Phys. Chem. C2018, 122, 5151−5160.(10) Wang, H.-C.; Wang, W.; Tang, A.-C.; Tsai, H.-Y.; Bao, Z.;Ihara, T.; Yarita, N.; Tahara, H.; Kanemitsu, Y.; Chen, S.; Liu, R.-S.High-Performance Novel CsPb1‑xSnxBr3 Perovskite Quantum Dotsfor Highly-Efficient Light-Emitting Diodes. Angew. Chem. Int. Ed.2017, 56, 13650−13654.(11) Wang, H.-C.; Lin, S.-Y.; Tang, A.-C.; Singh, B. P.; Tong, H.-C.;Chen, C.-Y.; Lee, Y.-C.; Tsai, T.-L.; Liu, R.-S. Mesoporous SilicaParticle Integrated with All-Inorganic CsPbBr3 Perovskite Quantum-Dot Nanocomposite (MP-PQDs) with High Stability and Wide ColorGamut Used for Backlight Display. Angew. Chem. Int. Ed. 2016, 55,7924−7929.(12) Xuan, T.; Yang, X.; Lou, S.; Huang, J.; Liu, Y.; Yu, J.; Li, H.;Wong, K.-L.; Wang, C.; Wang, J. High Stable CsPbBr3 Quantum DotsCoated with Alkyl Phosphate for White Light-Emitting Diodes.Nanoscale 2017, 9, 15286−15290.(13) Lou, S.; Xuan, T.; Yu, C.; Cao, M.; Xia, C.; Wang, J.; Li, H.Nanocomposites of CsPbBr3 Perovskite Nanocrystals in anAmmonium Bromide Framework with Enhanced Stability. J. Mater.Chem. C 2017, 5, 7431−7435.(14) Lou, S.; Xuan, T.; Liang, Q.; Huang, J.; Cao, L.; Yu, C.; Cao,M.; Xia, C.; Wang, J.; Zhang, D.; Li, H. Controllable and facilesynthesis of CsPbBr3-Cs4PbBr6 perovskite composites in pure polarsolvent. J. Colloid Interface Sci. 2019, 537, 384−388.(15) Hou, S.; Guo, Y.; Tang, Y.; Quan, Q. Synthesis andStabilization of Colloidal Perovskite Nanocrystals by MultidentatePolymer Micelles. ACS Appl. Mater. Interfaces 2017, 9, 18417−18422.(16) Lin, C. C.; Jiang, D.-H.; Kuo, C.-C.; Cho, C.-J.; Tsai, Y.-H.;Satoh, T.; Su, C. Water-Resistant Efficient Stretchable Perovskite-Embedded Fiber Membranes for Light-Emitting Diodes. ACS Appl.Mater. Interfaces 2018, 10, 2210−2215.(17) Li, Z.; Kong, L.; Huang, S.; Li, L. Highly Luminescent andUltra-stable CsPbBr3 Pervoskite Quantum Dots-silica/aluminaMonolith. Angew. Chem. Int. Ed. 2017, 56, 8134−8138.(18) Luo, B.; Pu, Y.-C.; Lindley, S. A.; Yang, Y.; Lu, L.; Li, Y.; Li, X.;Zhang, J. Z. Organolead Halide Perovskite Nanocrystals: BranchedCapping Ligands Control Crystal Size and Stability. Angew. Chem. Int.Ed. 2016, 55, 8864−8868.(19) Nguyen, H.-D.; Lin, C. C.; Liu, R.-S. Waterproof AlkylPhosphate Coated Fluoride Phosphors for Optoelectronic Materials.Angew. Chem. Int. Ed. 2015, 54, 10862−10866.(20) Pan, A.; Wang, J.; Jurow, M. J.; Jia, M.; Liu, Y.; Wu, Y.; Zhang,Y.; He, L.; Liu, Y. A General Strategy for the Preparation of StableLuminous Nanocomposite Inks Using Chemically AddressableCsPbX3 Peroskite Nanocrystals. Chem. Mater. 2018, 30, 2771−2780.(21) Woo, J. Y.; Kim, Y.; Bae, J.; Kim, T. G.; Kim, J. W.; Lee, D. C.;Jeong, S. Highly Stable Cesium Lead Halide Perovskite Nanocrystalsthrough in Situ Lead Halide Inorganic Passivation. Chem. Mater.2017, 29, 7088−7092.(22) Zhang, X.; Wang, H.-C.; Tang, A.-C.; Lin, S.-Y.; Tong, H.-C.;Chen, C.-Y.; Lee, Y.-C.; Tsai, T.-L.; Liu, R.-S. Robust and StableNarrow-Band Green Emitter: An Option for Advanced Wide-Color-Gamut Backlight Display. Chem. Mater. 2016, 28, 8493−8497.(23) Xuan, T.; Lou, S.; Huang, J.; Cao, L.; Yang, X.; Li, H.; Wang, J.Monodisperse and brightly luminescent CsPbBr3/Cs4PbBr6 perov-skite composite nanocrystals. Nanoscale 2018, 10, 9840−9844.(24) Sun, C.; Zhang, Y.; Ruan, C.; Yin, C.; Wang, X.; Wang, Y.; Yu,W. W. Efficient and Stable White LEDs with Silica-Coated InorganicPerovskite Quantum Dots. Adv. Mater. 2016, 28, 10088−10094.(25) Wei, Y.; Xiao, H.; Xie, Z.; Liang, S.; Liang, S.; Cai, X.; Huang,S.; Al Kheraif, A. A.; Jang, H. S.; Cheng, Z.; Lin, J. Highly

Luminescent Lead Halide Perovskite Quantum Dots in HierarchicalCaF2 Matrices with Enhanced Stability as Phosphors for White Light-Emitting Diodes. Adv. Opt. Mater. 2018, 6, 1701343.(26) Raja, S. N.; Bekenstein, Y.; Koc, M. A.; Fischer, S.; Zhang, D.;Lin, L.; Ritchie, R. O.; Yang, P.; Alivisatos, A. P. Encapsulation ofPerovskite Nanocrystals into Macroscale Polymer Matrices: EnhancedStability and Polarization. ACS Appl. Mater. Interfaces 2016, 8,35523−35533.(27) Wei, Y.; Deng, X.; Xie, Z.; Cai, X.; Liang, S.; Ma, P.; Hou, Z.;Cheng, Z.; Lin, J. Enhancing the Stability of Perovskite QuantumDots by Encapsulation in Crosslinked Polystyrene Beads via aSwelling-Shrinking Strategy toward Superior Water Resistance. Adv.Funct. Mater. 2017, 27, 1703535.(28) Wang, S.; Liu, K.; Yao, X.; Jiang, L. Bioinspired surfaces withsuperwettability: new insight on theory, design, and applications.Chem. Rev. 2015, 115, 8230−8293.(29) Feng, L.; Li, S.; Li, Y.; Li, H.; Zhang, L.; Zhai, J.; Song, Y.; Liu,B.; Jiang, L.; Zhu, D. Super-Hydrophobic Surfaces: From Natural toArtificial. Adv. Mater. 2002, 14, 1857−1860.(30) Wang, P.; Zhao, T.; Bian, R.; Wang, G.; Liu, H. RobustSuperhydrophobic Carbon Nanotube Film with Lotus Leaf MimeticMultiscale Hierarchical Structures. ACS Nano 2017, 11, 12385−12391.(31) Yabu, H.; Shimomura, M. Single-step fabrication of transparentsuperhydrophobic porous polymer films. Chem. Mater. 2005, 17,5231−5234.(32) Tsougeni, K.; Vourdas, N.; Tserepi, A.; Gogolides, E.;Cardinaud, C. Mechanisms of oxygen plasma nanotexturing oforganic polymer surfaces: from stable super hydrophilic to superhydrophobic surfaces. Langmuir 2009, 25, 11748−11759.(33) Li, Y.; Zhang, Z.; Ge, B.; Men, X.; Xue, Q. One-pot, template-free synthesis of a robust superhydrophobic polymer monolith with anadjustable hierarchical porous structure. Green Chem. 2016, 18,5266−5272.(34) Protesescu, L.; Yakunin, S.; Bodnarchuk, M. I.; Krieg, F.;Caputo, R.; Hendon, C. H.; Yang, R. X.; Walsh, A.; Kovalenko, M. V.Nanocrystals of cesium lead halide perovskites (CsPbX3, X= Cl, Br,and I): novel optoelectronic materials showing bright emission withwide color gamut. Nano Lett. 2015, 15, 3692−3696.(35) Sun, Q.; Aguila, B.; Verma, G.; Liu, X.; Dai, Z.; Deng, F.; Meng,X.; Xiao, F.-S.; Ma, S. Superhydrophobicity: constructing homoge-neous catalysts into superhydrophobic porous frameworks to protectthem from hydrolytic degradation. Chem 2016, 1, 628−639.(36) Lum, K.; Chandler, D.; Weeks, J. D. Hydrophobicity at Smalland Large Length Scales. J. Phys. Chem. B 1999, 103, 4570−4577.(37) Chen, X.; Zhang, F.; Ge, Y.; Shi, L.; Huang, S.; Tang, J.; Lv, Z.;Zhang, L.; Zou, B.; Zhong, H. Centimeter-Sized Cs4PbBr6 Crystalswith Embedded CsPbBr3 Nanocrystals Showing Superior Photo-luminescence: Nonstoichiometry Induced Transformation and Light-Emitting Applications. Adv. Funct. Mater. 2018, 28, 1706567.(38) Xin, Y.; Zhao, H.; Zhang, J. Highly Stable and LuminescentPerovskite-Polymer Composites from a Convenient and UniversalStrategy. ACS Appl. Mater. Interfaces 2018, 10, 4971−4980.(39) Loiudice, A.; Saris, S.; Oveisi, E.; Alexander, D. T. L.;Buonsanti, R. CsPbBr3 QD/AlOx Inorganic Nanocomposites withExceptional Stability in Water, Light, and Heat. Angew. Chem. Int. Ed.2017, 56, 10696−10701.(40) Wang, C.; Chesman, A. S. R.; Jasieniak, J. J. Stabilizing thecubic perovskite phase of CsPbI3 nanocrystals by using an alkylphosphinic acid. Chem. Commun. 2017, 53, 232−235.(41) Pan, J.; Shang, Y.; Yin, J.; De Bastiani, M.; Peng, W.; Dursun, I.;Sinatra, L.; El-Zohry, A. M.; Hedhili, M. N.; Emwas, A.-H.;Mohammed, O. F.; Ning, Z.; Bakr, O. M. Bidentate Ligand-PassivatedCsPbI3 Perovskite Nanocrystals for Stable Near-Unity Photo-luminescence Quantum Yield and Efficient Red Light-EmittingDiodes. J. Am. Chem. Soc. 2018, 140, 562−565.(42) Wei, Y.; Cheng, Z.; Lin, J. An overview on enhancing thestability of lead halide perovskite quantum dots and their applicationsin phosphor-converted LEDs. Chem. Soc. Rev. 2019, 48, 310−350.

Chemistry of Materials Article

DOI: 10.1021/acs.chemmater.8b04596Chem. Mater. 2019, 31, 1042−1047

1047