Mechanistic Investigation of Upconversion Photoluminescence in All

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Article

Mechanistic Investigation of Upconversion Photoluminescence in All Inorganic Perovskite CsPbBrI Nanocrystals 2

Shuai Ye, Mengjie Zhao, Minghuai Yu, Ming Zhu, Wei Yan, Jun Song, and Junle Qu J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.7b12175 • Publication Date (Web): 24 Jan 2018 Downloaded from http://pubs.acs.org on January 25, 2018

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The Journal of Physical Chemistry

Mechanistic Investigation of Upconversion Photoluminescence in All-Inorganic Perovskite CsPbBrI2 Nanocrystals Shuai Ye, Mengjie Zhao, Minghuai Yu, Ming Zhu, Wei Yan, Jun Song*, Junle Qu* Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, P. R. China

Abstract Perovskite quantum dots emit upconversion photoluminescence (UCPL) excited by long wavelength photons. However, UCPL with different wavelengths and widths are irradiated in perovskite colloidal excited by different energy photons. This study investigated efficient UCPL in colloidal CsPbBrI2 nanocrystals and proposed a simple energy level model to illustrate the UC mechanism. Redshifted UCPL relative to normal PL was attributed to recombination of carriers from the surface to the valance band and involved a single-photon process, whereas unshifted UCPL was attributed to recombination of carriers from the conduction band to the valance band and involved a two-photon process. Trap states within the valence band played an important role in the UC process. Single photon UC emission occurred when the absorbed photons possessed sufficient energy to excite electrons in deep trap states in CsPbBrI2 nanocrystals. However, when the photons could only excite electrons in shallow trap states, some excited photons were absorbed by shallow trap state, producing single photon UCPL, while the remaining photons were absorbed by the valance band, leading electrons transfer from the valance band to the conduction band. Therefore, the UC process was gradually dominated by the two-photon process as the incident photons energy was decreased.

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1

Introduction

Due to its ability to convert low energy photons to high energy photons1, upconversion has significant importance for many fields, such as bioimaging2,3, photovoltaic devices4,5, and sensors6. Upconversion photoluminescence (UCPL) has been widely observed in heterostructures of semiconductors7, triplet–triplet annihilation (TTA)8,9, quantum dots (QDs)10,11 and lanthanide doped upconversion nanoparticles (UCNPs)12,13. Existence of intermediate states was considered to be a prerequisite for UCPL, which could provide a transition level to absorb carriers excited by the first photon with subsequent transfer to higher energy states. The prototypical example was UCNPs, where low energy photons (infrared light) could be effectively converted into ultraviolet or visible photons due to their ladder-like energy levels14. However, such available intermediate states do not exist in colloidal QDs. In contrast, virtual levels, such as the surface state or interstitial defects known as trap states15, were always used to illustrate UC for QDs, such as InP16, CdTe17, and carbon QDs18. The halide perovskite QDs are novel colloidal nanocrystals and have received increasing attention due to their excellent optoelectronic properties and inexpensive cost19,20. These QDs exhibit tunable emission bands, narrow emission width, and high photoluminescence quantum yield (PLQY)21,22, and hence have significant potential in optoelectronic applications, such as LEDs and solar cells23-26. Perovskite QDs have also exhibited UCPL, excited by long wavelength photons27,28, but the UC mechanism has not been definitively identified previously. Therefore, this study investigated a series of optical properties for efficient UCPL in colloidal CsPbBrI2 nanocrystals and developed a probable UC mechanism.

2

Experimental

CsPbBrI2 nanocrystals were synthesized by the method as follows. PbBr2 (0.1 mmol), PbI2 (0.2 mmol), and Cs2CO3 (0.1 mmol) were mixed in a round bottom flask, and a


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solution of 10 ml octane, 0.5 ml oleic acid, and 0.5 ml oleylamine was added. The mixture was heated to 90°C in a water bath for 30 min and a red colloidal solution was obtained. The nanocrystal dispersions were held for one day to precipitate large nanocrystals, and the supernatant was retained for measurement. Sample morphologies were observed by transmission electron microscopy (TEM) (JEOL, Tokyo, Japan) with 100 kV accelerating voltage. Photoluminescence spectra were measured using an OCEAN QS65000 spectrofluorometer (Ocean Optics, Dunedin, FL, USA) under excitation laser with tunable wavelength of 400–1080 nm. Time resolved fluorescence measurements were performed using a Fluorolog®-3 steady-state spectrofluorometer equipped with a time correlated single photon counting (TCSPC) system.

3

Results and discussion

Figure 1a showed typical CsPbBrI2 nanocrystal morphology. The as-synthesized CsPbBrI2 nanocrystals were mono-dispersed cubic phase with average size ~14.2 nm. The high-resolution TEM (HRTEM) image in Figure 1b showed that the CsPbBrI2 NCs were single crystalline entities with a lattice spacing of 0.592 nm, corresponding with the (100) plane of the cubic perovskite CsPbX3 phase, which was also proved by the XRD pattern shown in Figure 1c. The CsPbBrI2 NCs exhibited single strong red emission centered at 627 nm (i.e., 1.978 eV) with 38.1 nm width, excited by 580 nm photons. This was the normal photoluminescence (PL) and attributed to carrier recombination from the conduction to the valance band, as shown in Figure 1d. Typical UCPL was also detected for CsPbBrI2 nanocrystals excited by long wavelength photons, as shown in Figures 1e and 1f. After excited by 660 nm photons, the nanocrystals exhibited a strong red emission centered at 638 nm (i.e., 1.944 eV) with a width of 28.3 nm. Compared with the normal PL peak, this UCPL showed 34 meV redshift in peak energy and narrower emission, which implied involvement of other energy states within the band gap. These energy states were most likely surface states. Under 700 nm photon excitation, the nanocrystals exhibited red strong emission at 630 nm (i.e., 1.968 eV) with a width of 35.7 nm. No obvious change of wavelength and width was evident



relative to the normal PL peak, indicating this UCPL may be related to carrier recombination from the conduction to the valance band. The discrepancy between the UCPL spectra indicated different UC mechanisms in nanocrystals excited by different energy photons.

Figure 1. CsPbBrI2 nanocrystal (a) TEM morphology (scale bar = 200 nm, inset shows size distribution), (b) HRTEM, (c) XRD pattern; and photoluminescence (PL) spectra excited by (d) 580 nm, (e) 660 nm, and (f) 700 nm photons

To investigate the UCPL emission discrepancy, UCPL spectra were measured when irradiated by photons from 650 to 900 nm at 10 nm steps, as shown in Figure 2. UCPL intensity decreased exponentially with increased photon wavelength from 640 to 700 nm and no excitation peak was detected. Reduced PL intensity indicated the existence of a series of trap states with various state densities in CsPbBrI2 nanocrystals29,30. Figure 3 shows the trap state energies, derived by measuring UCPL from 1 nm step irradiating photons over 640-700 nm (i.e., energy 1.771–1.935 eV). Although PL intensity generally reduced with increased photon energy, there were significant fluctuations, attributed to the trap states that could absorb photons with specific energy, as specifically noted in Figure 3. There was relatively little PL effect from increasing the photon wavelength beyond 700 nm, until a weak excitation peak


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centered at ~830 nm.

Figure 2. Photoluminescence (PL) of CsPbBrI2 nanocrystals excited by 650–900 nm wavelength incident photons

Figure 3. Photoluminescence (PL) of CsPbBrI2 nanocrystals excited by 1.771–1.935 eV incident photons

The dependence of emission band intensity on pump laser power was measured for CsPbBrI2 nanocrystals excited by different wavelength photons to investigate the UPCL



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mechanisms. In general, the number of photons required to populate the emitting state can expressed as31 𝐼𝑓 ∝ 𝑃𝑛 ,

(1)

where, If is the PL intensity, P is the pump laser power, and n is the number of required laser photons, as shown in Figure 4a. The n values were approximately 1 when the wavelength of the laser photon wavelength was shorter than 680 nm, indicating the resultant emission involved single-photon process. The n values were approximately 2 when the wavelength of the laser photons was longer than 700 nm, indicating the emission involved a two-photon process. Thus, considering the Figures. 1c and 1d, it was deduced UCPL emission from the single-photon process showed significant peak energy redshift; whereas the two-photon process showed no change relative to normal PL. Similar redshift UCPL have been observed previously for colloidal CdTe quantum dots. Thus, the single-photon UCPL emission of CsPbBrI2 nanocrystals was attributed to recombination of carriers from surface to band gap states, and the two-photon emission to recombination of carriers from the conduction to valance bands. While pump laser photons were 680–700 nm, the n values varied between 1 and 2 and were increased linearly with increasing the excited photon wavelength, which indicating the UCPL emission involved a balance of single-photon and two-photon processes. The involved UC process in CsPbBrI2 nanocrystals was dominated by single photon process when the CsPbBrI2 nanocrystals were excited by higher energy photons while dominated by two photon process when excited by lower energy photons. This balance was further confirmed by emission bands shift in CsPbBrI2 nanocrystals when excited by 695 nm laser with different power, as shown in Figure 4b. Under 695 nm excitation, The emission bands shifted monotonically from 638 nm to 627 nm with enhanced incident photons power from 20-200 mW, confirming that UC in CsPbBrI2 nanocrystals was dominated by a single-photon process when excited by higher power photons but a two-photon process when excited by lower power photons.


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Figure 4. a) n values of 𝐼𝑓 ∝ 𝑃𝑛 for CsPbBrI2 nanocrystals excited by different wavelength laser, b) PL spectra of CsPbBrI2 nanocrystals excited by 695 nm laser with different power

A simple energy level model was constructed to illustrate CsPbBrI2 nanocrystal UC mechanisms based on these outcomes, as shown in Figure 5. When photon energy exceeds the band gap (Eex > 1.978 eV), electrons in the valance band transfer to the conduction band, and the subsequent recombination of electrons and holes produces the normal PL emission. When photon energy is slightly less than the band gap (1.824 eV < Eex < 1.944 eV), electrons in deep trap states (yellow dashed line) are excited and transfer to the surface state. However, the generated holes in the deep trap states are unstable and quickly transfer to the valance band. Subsequent recombination with surface state electrons produces the observed UCPL emission. Gradually decreasing UCPL intensity, as shown in Figure 2, is caused by decreased trap state density. With further photon energy reduction (1.784 eV < Eex < 1.824 eV), only shallow trap states (green dashed line) can be excited. Some incident photons are absorbed by these shallow trap states, producing single-photon UCPL emission. However, shallow trap state density is too low to absorb all available photons, and the remainder are absorbed by electrons in the valance band, and transferred to the conduction band by a twophoton process. Therefore, when CsPbBrI2 nanocrystals were excited by lower energy photons, less photons were absorbed by the trap states, and more photons were absorbed by the valance band. As wavelength increased, the UC process was gradually dominated by the two-photon process. Similarly, when CsPbBrI2 nanocrystals were



excited by higher power photons (i.e., more photon numbers), the involved UC process was also dominated by two-photon process, which is consistent with Figure 4. When photon energy was insufficient to excite electrons in trap states into the surface state (Eex < 1.784 eV), only electrons in the valance band were excited in a two-photon process, transferred to the conduction band, and then recombined with holes in the valance band to produce PL emission. Thus, two-photon UCPL emission was relatively similar to normal PL emission.

Figure 5. Simplified energy diagram and upconversion photoluminescence (UCPL). CB: conduction band; VB: valance band; SS: surface state; STS: shallow trap state; DTS: deep trap state; TP: two-photon process.

To further explore the cause of redshifted UCPL, time resolved PL measurements were performed at the peak wavelengths of normal and redshifted UCPL, as shown in Figure 6. Normal PL and UCPL exhibit similar single exponential decay traces with 1.34 and 1.18 ns rise times, respectively. The normal PL decay curve was fitted by a single exponential decay with a lifetime of 31.6 ns. This corresponds to the single decay channel for excited carriers, and is consistent with previous report32. In contrast, the UCPL decay curve was fitted by dual exponential decay with lifetimes of 3.25 and 37.6 ns. The shorter lifetime component was attributed to nonradiative carrier depopulation


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from trap bands, and the longer lifetime component to surface states involved in the UCPL process. In previous report, the thermal model had been used to explain the UCPL in semiconductor QDs such as CdTe and InP33. It has been also proved that the thermally assisted detrapping of electrons/holes from trap states to the conduction/valence band must take place prior to effective charge transport in organolead halide perovskite film34. The thermal model was also applicable in perovskite CsPbX3 QDs because the photoluminescence intensity was also influenced by temperature35. Here, we propose the thermal excitation model to explain the mechanism. Electrons are excited from the trap bands to the surface state, and then holes in the sub-valance bands were non-radiatively transferred to the valence band by thermal excitation. Subsequent recombination of electrons and holes from the surface state and valence bands, respectively, produces the observed UCPL with extended lifetime compared to normal PL. This proposed mechanism is consistent with Figure 5.

Figure 6. CsPbBrI2 nanocrystal photoluminescence (PL) decay after excitation with 570 and 660 nm photons. Inset is enlarged PL decay from -5 to 30 ns

4

Conclusion

In conclusion, we investigated efficient UCPL in colloidal CsPbBrI2 nanocrystals and



proposed a simple energy level model to illustrate the UC mechanism. These cubic nanocrystals emitted normal PL centered at 627 nm when excited by short wavelength photons. But two UCPL pathways were irradiated when excited by long wavelength photons. When excited by 640-680 nm incident photons, redshifted UCPL centered at 638 nm relative to normal PL was detected, which was attributed to recombination of carriers from the surface to the valance band, and involved a single-photon process. In contrast, when excited by 700 nm or longer incident photons, the CsPbBrI2 nanocrystals emitted 627 nm again, which was attributed to recombination of carriers from the conduction band to the valance band, and involved a two-photon process. Trap states within the valance band explained the difference. The trap states involved gradually transformed from deep to shallow trap states. Single-photon UC emission occurred when the absorbed photons possessed sufficient energy to excite electrons in deep trap states in CsPbBrI2 nanocrystals. However, when the photons could only excite electrons in shallow trap states, although some incident photons were absorbed by shallow trap state, producing single photon UCPL, the remaining photons were absorbed by the valance band and electrons were transferred from the valance band into the conduction band. Therefore, the UC process was gradually dominated by the two-photon process as incident photons energy decreased.

AUTHOR INFORMATION Corresponding Authors: *E-mail: [email protected] *E-mail: [email protected] ORCID Shuai Ye: 0000-0002-9862-4983

Notes The authors declare no competing financial interest.

Acknowledgements This work were supported by the National Natural Science Foundation of China (61605124, 61775145, 31771584, 61620106016, 61525503, 61505118); the National


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Basic Research Program of China (2015CB352005); the Guangdong Natural Science Foundation (2014A030312008, 2017B020210006); Hong Kong, Macao, and Taiwan cooperation innovation platform & major projects of international cooperation in Colleges and Universities in Guangdong Province (2015KGJHZ002); Shenzhen Basic Research

Project

(JCYJ20170412110212234,

JCYJ20170412105003520,

JCYJ20160328144746940, JCYJ20160308093035903, JCYJ20160422151611496, GRCK2017042110420047).

References (1) Auzel F. Upconversion and Anti-Stokes Processes with f and d Ions in Solids, Chem. Rev., 2004, 104(1), 139-173. (2) Zhou J., Liu Z., Li F. Upconversion Nanophosphors for Small-animal Imaging, Chem. Soc. Rev., 2012, 41, 1323-1349. (3) Idris N. M., Gnanasammandhan M. K., Zhang J., Ho P. C., Mahendran R., Zhang Y.. In vivo Photodynamic Therapy Using Upconversion Nanoparticles as Remotecontrolled Nanotransducers, Nat. Med., 2012, 18(10), 1580-1586. (4) Cheng Y. Y., Fuckel B., MacQueen R. W., Khoury T., Clady R.G. C. R., Schulze T. F., Ekins-Daukes N. J., Crossley M. J., Stannowski B., Lips K., et al. Improving the Light-harvesting of Amorphous Silicon Solar Cells with Photochemical Upconversion, Energy Environ. Sci., 2012, 5, 6953-6959. (5) Wild J. d., Rath J. K., Meijerink A., Sark W, Schropp R.. Enhanced Near-infrared Response of a-Si:H Solar Cells with β-NaYF4:Yb3+18%, Er3+2% Upconversion Phosphors, Solar Energy Materials & Solar Cells, 2014, 94, 2395-2398. (6) Chan E. M., Han G., Goldberg J. D., Gargas D. J., Ostrowski A. D., Schuck P. J., Cohen B. E., Milliron D. J.. Combinatorial Discovery of Lanthanide-Doped Nanocrystals with Spectrally Pure Upconverted Emission, Nano Lett. 2012, 12, 3839-3845. (7) Cheong H. M., Fluegel B., Hanna M. C., Mascarenhas A. Photo Luminescence Upconversion in GaAs/AlxGa1-xAs Heterostructures, Phys. Lett. B 1998, 18(10),



R4253-R4256. (8) Yu X., Cao X., Chen X., Ayres N., Zhang P.. Triplet–triplet Annihilation Upconversion from Rationally Designed Polymeric Emitters with Tunable Interchromophore Distances, Chem. Commun., 2015, 51, 588-591. (9) Cheng Y. Y., Khoury T., Clady R. G. C. R., Tayebjee M. J. Y., Ekins-Daukes N. J., Crossley M. J., Schmidt T. W.. On the Efficiency Limit of Triplet–triplet Annihilation for Photochemical Upconversion, Phys. Chem. Chem. Phys., 2010, 12, 66-71. (10) Huang Z., Xu Z., Mahboub M., Li X., Taylor J. W., Harman W. H., Lian T., Tang M. L.. PbS/CdS Core–Shell Quantum Dots Suppress Charge Transfer and Enhance Triplet Transfer, Angew. Chem. Int. Ed. 2017, 56, 16583-16587. (11) Deutsch Z., Neeman L., Oron D.. Luminescence Upconversion in Colloidal Double Quantum Dots, Nat. Nanotech., 2013, 8, 649-653. (12) Wang J., Deng R., MacDonald M. A., Chen B., Yuan J., Wang F., Chi D., Hor T. S. A., Zhang P., Liu G., Et al. Enhancing Multiphoton Upconversion Through Energy Clustering at Sublattice level, Nat. Mater. 2014, 13, 157-162. (13) Chen X., Peng D., Jua Q., Wang F. Photon Upconversion in core-shell Nanoparticles, Chem. Soc. Rev., 2015, 44, 1318-1330 (14) Chen G., Ohulchanskyy T. Y., Kachynski A., Agren H., Prasad P. N.. Intense Visible and Near-Infrared Upconversion Photo luminescence in Colloidal LiYF4:Er3+ Nanocrystals under Excitation at 1490 nm, ACS Nano, 2011, 5, 49814986 (15) Zhu M., Mi Y., Zhu G., Li D., Wang Y., Weng Y.. Determination of Midgap State Energy Levels of an Anatase TiO2 Nanocrystal Film by Nanosecond Transient Infrared Absorption-Excitation Energy Scanning Spectra, J. Phys. Chem. C, 2013, 117, 18863-18869 (16) Ignatiev I. V., Kozin I. E., Ren H., Sugou S., Masumoto Y.. Anti-Stokes Photoluminescence of InP Self-assembled Quantum Dots in the Presence of Electric Current, Physical Review B, 1999, 60, , R14001-R14004 (17) Wang X., Yu W. W., Zhang J., Aldana J., Peng X., Xiao M.. Photoluminescence


Page 12 of 15

Page 13 of 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Upconversion in Colloidal CdTe Quantum Dots, Phys. Lett. B, 2003, 68, 125318 (18) Li H., He X., Kang Z., Huang H., Liu Y., Liu J., Lian S., Tsang C. H. A., Yang X., Lee S.. Water-Soluble Fluorescent Carbon Quantum Dots and Photocatalyst Design, Angew. Chem. Int. Ed. 2010, 122, 4532-4536 (19) Protesescu L., Yakunin S., Bodnarchuk M. I., Krieg F., Caputo R., Hendon C. H., Yang R. Xi, Walsh A., Kovalenko M. V.. Nanocrystals of Cesium Lead Halide Perovskites (CsPbX3, X = Cl, Br, and I): Novel Optoelectronic Materials Showing Bright Emission with Wide Color Gamut. Nano Lett. 2015, 15, 3692-3696 (20) Zhang F., Zhong H., Chen C., Wu X., Hu X., Huang H., Han J., Zou B., Dong Y.. Brightly Luminescent and Color-Tunable Colloidal CH3NH3PbX3(X=Br, I, Cl) Quantum Dots: Potential Alternatives for Display Technology, ACS Nano, 2015, 9, 4533-4542 (21) Liu F., Zhang Y., Ding C., Kobayashi S., Izuishi T., Nakazawa N., Toyoda T., Ohta T., Hayase S., Minemoto T., et al. Highly Luminescent Phase-Stable CsPbI3 Perovskite Quantum Dots Achieving Near 100% Absolute Photoluminescence Quantum Yield, ACS Nano 2017, 11, 10373-10383 (22) Ye S., Yu M., Yan W., Song J., Qu J.. Enhanced Photoluminescence of CsPbBr3@Ag Hybrid Perovskite Quantum Dots, J. Mater. Chem. C, 2017, 5, 81878193 (23) Chistyakov A. A., Zvaigzne M. A., Nikitenko V. R., Tameev A. R., Martynov I. L., Prezhdo O. V.. Optoelectronic Properties of Semiconductor Quantum Dot Solids for Photovoltaic Applications, J. Phys. Chem. Lett., 2017, 8 (17), 4129-4139 (24) Wang Y., Li X., Song J., Xiao L., Zeng H., Sun H.. All-Inorganic Colloidal Perovskite Quantum Dots: A New Class of Lasing Materials with Favorable Characteristics, Adv. Mater. 2015, 27, 7101-7108 (25) Chen J., Žídek K., Chábera P., Liu D., Cheng P., Nuuttila L., Al-Marri M. J., Lehtivuori H., Messing M. E., Han K., et al. Size- and Wavelength-Dependent TwoPhoton Absorption Cross-Section of CsPbBr3 Perovskite Quantum Dots, J. Phys. Chem. Lett., 2017, 8 (10), 2316-2321 (26) Zhang D., Yang Y., Bekenstein Y., Yu Y., Gibson N. A., Wong A. B., Eaton S. W.,



Kornienko N., Kong Q., Lai M., et al. Synthesis of Composition Tunable and Highly Luminescent Cesium Lead Halide Nanowires through Anion-Exchange Reactions, J. Am. Chem. Soc. 2016, 138, 7236-239 (27) Qiu Y., Nan F., Wang Q., Liu X., Ding S., Hao Z., Zhou L., Wang Q.. Tuning the Competitive Recombination of Free Carriers and Bound Excitons in Perovskite CH3NH3PbBr3 Single Crystal, J. Phys. Chem. C 2017, 121, 6916-6923 (28) Ye S., Yu M., Zhao M., Song J., Qu J. Low Temperature Synthesis of High-quality All-inorganic Cesium Lead Halide Perovskite Nanocrystals in Open Air and Their Upconversion Luminescence, Journal of Alloys and Compounds, 2018, 730, 62-70 (29) Kang J., Wang L. High Defect Tolerance in Lead Halide Perovskite CsPbBr3, J. Phys. Chem. Lett. 2017, 8, 489−493 (30) Shi D., Adinolfi V., Comin R., Yuan M., Alarousu E., Buin A., Chen Y., Hoogland S., Rothenberger A., Katsiev K., et al. Low Trap-state Density and Long Carrier Diffusion in Organolead Trihalide Perovskite Single Crystals, Science, 2015, 374, 519-522 (31) Ye S., Chen G., Shao W., Qu J., Prasad P. N. Tuning Upconversion Through a Sensitizer/activator-isolated NaYF4 Core/shell Structure, Nanoscale, 2015, 7, 39763984 (32) Zhu Z., Yang Q., Gao L., Zhang L., Shi A., Sun C., Wang Q., Zhang H. SolventFree Mechanosynthesis of Composition-Tunable Cesium Lead Halide Perovskite Quantum Dots, J. Phys. Chem. Lett. 2017, 8, 1610−1614 (33) Poles E., Selmarten D. C., Micic O. I., Nozik A. J.. Anti-Stokes Photoluminescence in Colloidal Semiconductor Quantum Dots, Appl. Phys. Lett. 1999, 75, 971-973 (34) Wang Y., Wang H., Yu M., Fu L., Qin Y., Zhang J., Ai X. The Influence of Morphology and PbI2 on the Intrinsic Trap State Distribution in Perovskite Films Determined by Using Temperature-Dependent Fluorescence Spectroscopy, ChemPhysChem, 2017, 18, 310 –317 (35) Lee S. M., Moon C. J., Lim H., Lee Y., Choi M. Y., Bang J.. TemperatureDependent Photoluminescence of Cesium Lead Halide Perovskite Quantum Dots: Splitting of the Photoluminescence Peaks of CsPbBr3 and CsPb(Br/I)3 Quantum


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Dots at Low Temperature, J. Phys. Chem. C 2017, 121, 26054-26062

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Mechanistic Investigation of Upconversion Photoluminescence in All

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