Letter Cite This: J. Phys. Chem. Lett. 2019, 10, 3248−3253
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Ultralow-Threshold and Color-Tunable Continuous-Wave Lasing at Room-Temperature from In Situ Fabricated Perovskite Quantum Dots Lei Wang,† Linghai Meng,† Lan Chen,‡ Sheng Huang,† Xiangang Wu,† Guang Dai,§ Luogen Deng,§ Junbo Han,∥ Bingsuo Zou,§ Chunfeng Zhang,‡ and Haizheng Zhong*,†
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†
Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems, School of Materials Science & Engineering, Beijing Institute of Technology, 5 Zhongguancun South Street, Haidian District, Beijing 100081, China ‡ National Laboratory of Solid State Microstructures, School of Physics & Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China § School of Physics, Beijing Institute of Technology, 5 Zhongguancun South Street, Haidian District, Beijing 100081, China ∥ Wuhan National High Magnetic Field Center and Department of Physics, Huazhong University of Science and Technology, Wuhan 430074, China S Supporting Information *
ABSTRACT: Room-temperature-operated continuous-wave lasers have been intensively pursed in the field of on-chip photonics. The realization of a continuous-wave laser strongly relies on the development of gain materials. To date, there is still a huge gap between the current gain materials and commercial requirements. In this work, we demonstrate continuous-wave lasers at room temperature using rationally designed in situ fabricated perovskite quantum dots in polyacrylonitrile films on a distributed feedback cavity. The achieved threshold values are 15, 24, and 58 W/cm2 for green, red, and blue lasers, respectively, which are one order lower than the reported values for the conventional CdSe quantum dot-based continuous-wave laser. Except for the high photoluminescence quantum yields, smooth surface, and high thermal conductivity of the resulting films, the key success of an ultralow laser threshold can be explained by the interaction of polyacrylonitrile and perovskite induced “charge spatial separation” effects. This progress opens up a door to achieve on-chip continuous-wave lasers for photonic applications.
A
to realize color-tunable lasers due to their superior photoluminescence (PL) properties and low lasing threshold.19−30 Up to now, they still do not meet the most concerned requirements of CW lasers in terms of Auger recombination, thermal conductivity, and surface roughness.31 In situ fabricated perovskite quantum dots (PQDs) in a polymeric matrix provide highly luminescent composite films with advantageous features of tunable emission and easy integration.32,33 The combination of these films with the photonic cavity is expected to be one of the promising routes for roomtemperature-operated CW lasers. In this work, we realized a color-tunable room-temperatureoperated CW laser by depositing rationally designed PQDembedded polyacrylonitrile (PAN) films on a DFB cavity. PQD-embedded PAN films were selected as gain materials due to their unique features to meet the requirements for CW lasers. First, the crystallization of PAN and MAPbX3 can be
s one of the keystone components for modern photonics, the on-chip continuous-wave (CW) laser has been intensively pursed.1 Although organic fluorescent materials embedded in a polymeric matrix have the potential to achieve a CW laser, they still suffer from the limited color tunability and serious photobleaching effects.2 The development of nanomaterials provides new emitters as gain materials to accomplish lasers, including colloidal quantum dots (QDs),3−7 semiconductor nanowires,8−10 and two-dimensional materials.11,12 Despite great success that has been made in the past years, there is still a huge gap between the current performance and commercial requirements. Halide perovskites are emerging as attractive materials for photonic and optoelectronic applications.13−15 Very recently, red emissive CW lasers based on CH3NH3PbI3 (MAPbI3, MA = CH3NH3+) based polycrystalline films have been realized with a distributed feedback (DFB) cavity.16−18 However, these materials need to be rationally designed toward broad color tunability, easy integration, as well as improved stability. The goal of on-chip color-tunable CW lasers at room temperature is still an extreme challenge. Perovskite-based nanomaterials (nanocrystals, nanowires, nanoplatelets) have been considered as a desired gain medium © 2019 American Chemical Society
Received: March 8, 2019 Accepted: May 14, 2019 Published: May 14, 2019 3248
DOI: 10.1021/acs.jpclett.9b00658 J. Phys. Chem. Lett. 2019, 10, 3248−3253
Letter
The Journal of Physical Chemistry Letters
Figure 1. (a) Transmittance and PL spectra of the in situ fabricated MAPbBr3 PQD-embedded PAN film. The inset shows an optical image of the film under daylight and UV light. (b) 5 μm × 5 μm AFM image of the 1.9 μm thick film spin-coated on quartz glass. The root-mean-square (RMS) roughness of the film is 0.784 nm. (c) Thermal conductivities of the film at different temperatures. (d) Schematic setup of the room-temperature CW lasing measurement. The inset shows an SEM image of the grating. (e) Emission spectra of the film on the DFB cavity and (f) emission intensity at 538.7 nm as a function of excitation power.
separated to control the size and distribution of these in situ fabricated PQDs in polymeric films. In addition, the resulting PQDs can be well-capped by PAN to suppress nonradiative recombination. Second, the interaction between PQDs and PAN greatly reduces the laser threshold. The phenomenon is similar to that observed by Klimov et al. on engineered CdSebased QD-based low-threshold lasers.34 Last but not least, PQD-embedded PAN films have high PL quantum yields (PLQYs) and high thermal conductivity and can form very uniform high-quality films through spin-coating. As a result of the above benefits, green, red, and blue room-temperature CW edge-emitting lasing with ultralow thresholds of 15, 24, and 58 W/cm2, respectively, were achieved. The threshold values of these PQD-based CW lasers are one order lower than the reported values for conventional CdSe QD-based CW lasers.4−6,12 PQDs in PAN films were fabricated following a modified method of our previous report (see the Experimental Section therein).32 A mixture of MAX2, PbX2, and PAN (molecular weight 150 000) was dissolved in N,N-dimethylformamide (DMF) and stirred vigorously for 8 h to form a transparent precursor solution. The precursor solution was spin-coated onto a substrate. After that, the substrates were moved into a vacuum oven. With the drying process, strong emissive PQD-embedded PAN films were obtained. Figure 1a shows the transmittance and PL spectra of resulting in situ fabricated CH3NH3PbBr3 (MAPbBr3)-based PQD-embedded PAN films. The inset displays photographs of a typical film under ambient light and UV irradiation. Even under daylight illumination, brilliant green emission can be observed. These films show very high transparency with transmittance of about 90% at the longer wavelength of the absorption band edge, suggesting a homogeneous distribution
of MAPbBr3 PQDs in a polymeric matrix. The uniform distribution of MAPbBr3 PQDs is also supported by the transmission electron microscopy (TEM) observations (Figure S1, Supporting Information). We further measured the PLQY of these films using a fluorescence spectrometer equipped with an integrated sphere with an excitation wavelength of 405 nm. The optimized green emissive films show near-unity efficiency with PLQYs of 95−97%. The high QY is supported by the temperature-dependent PL spectra (Figure S2, Supporting Information). The integrated PL intensity changes little when the temperature decreases from 300 to 4.2 K. Moreover, the film shows excellent monoexponential PL decay at temperatures ranging from 200 to 400 K (Figures S3 and S4, Supporting Information). For example, the decay curve at 200 K can be a monoexponentially fitted goodness-of-fit (χR2) at a value of 1.38, and the degree-of-freedom adjusted coefficient of determination (Adj. R-Square) is at a value of 0.9997 with 12000 photon counts. To our knowledge, the outstanding ensemble monoexponential PL decay of MAPbBr3 QDs has not been observed in previous literature. As we all know, the surface stoichiometry and surface ligands of QDs are dominating factors in determining their PL properties.35,36 These results indicate that PANs are effective ligands to cap the surface of in situ fabricated PQDs. The uniform surface and thermal conductivity of PQDembedded polymeric films are the other two important factors affecting the lasing threshold.12,37 By optimizing the fabrication parameters, we obtained very smooth MAPbBr3-based PQDembedded PAN films. Figure 1b shows 5× 5 μm2 top-view atomic force microscopy (AFM) images of the film spin-coated quartz glass with a thickness of 1.9 μm. The RMS roughness of these films approaches 0.784 nm. Figure 1c shows thermal conductivity (κ) curve of the resulting MAPbBr3-based PQD3249
DOI: 10.1021/acs.jpclett.9b00658 J. Phys. Chem. Lett. 2019, 10, 3248−3253
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The Journal of Physical Chemistry Letters
Figure 2. (a) Absorption spectra of the MAPbBr3 QDs in a PAN matrix, PVDF matrix, and n-hexane solution. (b) PL delays of the film on the cavity at low and high excitation power. (c) TRES of the film measured at 78 K. (d) Transient luminescence spectra at different time delays, along with the steady-state luminescence spectrum. The biexciton (XX) binding is extracted from two Gaussian fits of the delay spectra (∼0 ps), as shown by the two shaded areas. (e) Normalized PL spectra of the film under different pump power. The high-energy emission band corresponds to the biexciton emission band. (f) Evolution of the emission band intensity versus the pump intensity. The growth of the high-energy emission band shows a log−log slope of m = 2. It is consistent with the biexciton mechanism.
embedded PAN films at different temperatures. The κ value of a 1.9 μm film is about 1.2 W m−1 K−1 at room temperature, which is higher than that of most commercially available polymers (Table S1 in the Supporting Information).38,39 In summary, the low nonradiative recombination, high uniformity, quite smooth surface, and high thermal conductivity enable the possibility to achieve a low-threshold roomtemperature CW laser. We then explored the optically pumped lasing by incorporating MAPbBr3-based PQD-embedded PAN films into a DFB optical cavity (see the experimental details in the Supporting Information). Figure S5 shows the designed DFB structure for CW lasing. The first-order, second-order, and high-order gratings were simulated by applying COMSOL Multiphysics software, and the results are shown in Figures S6−S8. Because of the high viscosity of the perovskite precursor solution, it was not possible to obtain flat and thin PQD−PAN films less than 1.5 μm. In our work, the fifth-order grating was applied to generate CW lasing. Figure 1d shows the schematic diagram of the experimental measurements, and the inset shows the scanning electron microscope (SEM) image of the grating. A 405 nm semiconductor CW laser is used as the excitation beam. The output lasing emission is collected by using a fiber-optic spectrometer with a spectral resolution of 0.18 nm. The evolution of the emission spectra under different excitation power is depicted in Figure 1e. At low excitation power, the PL spectra are dominated by spontaneous emission. With increasing excitation power, narrow lasing peaks appear, indicating the evolution from spontaneous emission to stimulated emission due to the increase of temporal coherence. The fwhm (full width at half-maximum) of the laser peak at 538.7 nm is 0.45 nm, corresponding to a Q value of ∼1200. Figure 1f plots the emission intensity at 538.7 nm as a function of excitation power. The CW lasing threshold power is as low
as 15 W/cm2, which is the lowest compared with the reported solution-processed green CW lasers (Table S2, Supporting Information). The lasing emission was further studied by applying polarization measurement (see Figure S9, Supporting Information). As shown in Figure S10, the lasing intensity decreases gradually with increasing degree of detection polarization, with a minimum at 90°. In addition, similar lasing emission was also observed when pumping the sample using a femtosecond-pulsed laser (see Figure S11, Supporting Information). To understand the interactions between PAN and PQDs, we conducted comparative investigations of PQDs in the polymeric matrix of PAN and PVDF as well as in n-hexane solution. Figure 2a shows the absorption spectra of the MAPbBr3 PQDs in different media. It is noted that the intensities of the exciton absorption peaks differ compared to each other. The observations suggest that the interaction between PAN and PQDs strongly affects their optical properties.40 We then performed time-resolved PL measurement on PQD-embedded PAN films. Figure 2b shows the PL decays of the film in the cavity recorded at the peak wavelength at low and high excitation power. The PL decay curve at low excitation power (0.03 mW) can be fitted by a monoexponential decay function with τ = 10.80 ± 0.18 ns. At high excitation power (17 mW), fast PL decay components emerged. The long-time components of the PL traces at low and high excitation power are very similar, which can be assigned to single-exciton recombination. Subtracting the single-exciton component from the low-intensity decay trace, two fast decay components with decay constants of 0.7 ± 0.02 and 3.67 ± 0.1 ns can be obtained (Figure S12, Supporting Information). It is noticed that the slow component is about 5 times longer than the fast one. A similar phenomenon has also been observed in colloidal CsPbBr3 PQDs.41,42 The fast 3250
DOI: 10.1021/acs.jpclett.9b00658 J. Phys. Chem. Lett. 2019, 10, 3248−3253
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Figure 3. Charge densities at the VBM (left) and CBM (right) states of the MAPbBr3 PQD surrounded by PAN (upper), n-octylamine (middle), and PVDF (lower). All have an isosurface value of 0.0006 e/Bohr3. The L represents ligand (PAN, PVDF, n-octylamine) capping on MAPbBr3 PQDs. The yellow and blue isosurfaces correspond to the electron increase and depletion zones. H, white; C, pink; Pb, black; Br, brown; N, gray; F, green.
Figure 4. (a) Lasing emission spectra of the blue and red PQD-embedded PAN films on DFB cavities. (b) Emission intensity at 482 and 614 nm as a function of excitation power. The thresholds for the blue and red lasing are 58 and 24 W/cm2, respectively.
10 MHz repetition rate, 10 mW). Two emission bands with peaks at ∼523 and ∼531 nm can be observed. The intensity of the high-energy band is higher than that of the low-energy one at t = 0. However, the high-energy band emission decays fast with a time constant of ∼3.8 ns, and the spectra converge to the steady-state emission. To calculate Δxx, the transient PL spectrum is fitted by two Gaussian curves, and the spacing between the two bands gives a Δxx of 42.7 meV. The positive Δxx at room temperature was further confirmed by the excitation power-dependent steady PL measurements. As shown in Figure 2e, an emission band on the high-energy side increases with increasing excitation power. The highenergy band intensity shows quadratic growth with the excitation power, revealing the high-energy emission coming from biexcitons (Figure 2f). The X−X repulsion could move the absorbing transition away from the emission band, which reduces the lasing threshold.34 The positive biexciton binding energy can be explained to the “charge spatial separation” of electron and hole wave functions.
fraction can be attributed to biexciton recombination, while the slow one corresponds to the recombination of trions. The biexciton recombination was further studied by considering the influence of PAN on the biexciton interaction energy (Δxx) of MAPbBr3 PQDs. As we known, the strong reabsorption consumes the emitted photons and blocks gain building. The reabsorption in MAPbBr3 PQDs is large because of the small Stoke shift (∼40 meV).43 The positive Δxx can suppress the reabsorption effect by reducing the overlap between the absorption band and emission band.34 Δxx is determined by the competition of Coulomb forces between the two electrons and two holes. It is reported that the Δxx values of colloidal CsPbBr3 and CsPbI3 PQDs are negative, corresponding to attractive exciton−exciton (X−X) interaction.41,44 However, our results show that the Δxx of in situ fabricated MAPbBr3 PQDs is positive. Figure 2c shows the time-resolved emission spectra (TRES) of the films at 77 K, and Figure 2d presents the corresponding transient PL spectra recorded at different time delays, together with the steady PL spectra under an excitation at 375 nm (45 ps pulse duration, 3251
DOI: 10.1021/acs.jpclett.9b00658 J. Phys. Chem. Lett. 2019, 10, 3248−3253
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The Journal of Physical Chemistry Letters To further illustrate the influence of PAN on MAPbBr3 QDs, the wave function distribution was calculated by applying density functional theory (DFT) (see the experimental details in the Supporting Information).45,46 Figure 3 compares the charge densities at the valence band maximum (VBM) and conduction band minimum (CBM) states with an isosurface value of 0.0006 e/Bohr3 for PAN (upper), n-octylamine (middle), and PVDF (lower) capped PQDs. By comparing the state distribution of the CBM, we found that the electron cloud of CBM states could be strongly affected by the surface ligands. Specifically, most of the electron cloud was located at the surface of the MAPbBr3 QD when interacted with PAN. However, the CBM states of n-octylamine or PVDF capped MAPbBr3 PQDs had a very limited electron cloud on the surface. The charge density of the VBM was reduced due to the interaction with PAN, suggesting shifting of the hole wave function to the surface as well as the spatial separation of electrons and hole wave functions. On the basis of the experimental and calculation results, it is deduced that PQDs in the PAN show charge spatial separation effects. However, further study is necessary to clarify the mechanisms of the achieved ultralow threshold. By varying the PbX2 salts in the precursors, we also obtained blue and red emissive MAPbX3 (X = Br, I, Cl) PQDs in a PAN matrix with emission peaks at 480 and 610 nm, respectively (Figures S13−S15, Supporting Information). As shown in Figure 4a, room-temperature-operated blue and red CW lasing emissions were also achieved by using five-order DFB cavities. The thresholds for the laser peaks at 482 and 614 nm are 58 and 24 W/cm2, with corresponding Q factors of 910 and 1330, respectively (Figure 4b). In summary, the in situ fabricated PQDs in a PAN matrix have high transmittance (∼90%), near-unity PLQYs (up to 97%), a very smooth surface (RMS roughness: 0.784 nm), and high thermal conductivity (∼1.2 W m−1 K−1). More importantly, the resulting PQDs show unique features of charge spatial separation effects due to the interactions between in situ fabricated PQDs and the PAN matrix. The combination of these effects enables easy realization of colortunable PQD-based CW lasers at room temperature for the first time. The thresholds of green, blue, and red CW lasers at room temperature are as low as 15, 58, and 24 W/cm2, respectively, which are one order magnitude lower than those in recent reports of QD CW lasers. The ultralow threshold of PQD-based CW lasers makes them very suitable for LED pumping, showing bright potential to integrate the laser source into on-chip photonics.
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polarization emission character of the laser at different detection, and additional sample characterization data (PDF)
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Junbo Han: 0000-0002-5072-4897 Bingsuo Zou: 0000-0003-4561-4711 Chunfeng Zhang: 0000-0001-9030-5606 Haizheng Zhong: 0000-0002-2662-7472 Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was supported by the National Key R&D Program (No. 2017YFB0404600) and National Natural Science Foundation of China (61722502, 61705009) and BIT funds.
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REFERENCES
(1) Zhou, Z.; Yin, B.; Michel, J. On-Chip Light Sources for Silicon Photonics. Light Sci. Appl. 2015, 4, e358−e358. (2) Kuehne, A. J. C.; Gather, M. C. Organic Lasers: Recent Developments on Materials, Device Geometries, and Fabrication Techniques. Chem. Rev. 2016, 116, 12823−12864. (3) Klimov, V. I.; Mikhailovsky, A. A.; Xu, S.; Malko, A.; Hollingsworth, J. A.; Leatherdale, C. A.; Eisler, H.; Bawendi, M. G. Optical Gain and Stimulated Emission in Nanocrystal Quantum Dots. Science 2000, 290, 314−347. (4) Grim, J. Q.; Christodoulou, S.; Di Stasio, F.; Krahne, R.; Cingolani, R.; Manna, L.; Moreels, I. Continuous-Wave Biexciton Lasing at Room Temperature Using Solution-Processed Quantum Wells. Nat. Nanotechnol. 2014, 9, 891−895. (5) Fan, F.; Voznyy, O.; Sabatini, R. P.; Bicanic, K. T.; Adachi, M. M.; McBride, J. R.; Reid, K. R.; Park, Y. S.; Li, X.; Jain, A.; QuinteroBermudez, R.; Saravanapavanantham, M.; Liu, M.; Korkusinski, M.; Hawrylak, P.; Klimov, V. I.; Rosenthal, S. J.; Hoogland, S.; Sargent, E. H. Continuous-Wave Lasing in Colloidal Quantum Dot Solids Enabled by Facet-Selective Epitaxy. Nature 2017, 544, 75−79. (6) Chien, H. C.; Cheng, C. Y.; Mao, M. H. Continuous Wave Operation of SiO2 Sandwiched Colloidal CdSe/ZnS Quantum-Dot Microdisk Lasers. IEEE J. Sel. Top. Quantum Electron. 2017, 23, 1−5. (7) Wu, K.; Park, Y. S.; Lim, J.; Klimov, V. I. Towards ZeroThreshold Optical Gain Using Charged Semiconductor Quantum Dots. Nat. Nanotechnol. 2017, 12, 1140−1147. (8) Pan, A.; Zhou, W.; Leong, E. S. P.; Liu, R.; Chin, A. H.; Zou, B.; Ning, C. Z. Continuous Alloy-Composition Spatial Grading and Superbroad Wavelength-Tunable Nanowire Lasers on a Single Chip. Nano Lett. 2009, 9, 784−788. (9) Eaton, S. W.; Fu, A.; Wong, A. B.; Ning, C. Z.; Yang, P. Semiconductor Nanowire Lasers. Nat. Rev. Mater. 2016, 1, 16028. (10) Gargas, D. J.; Toimil-Molares, M. E.; Yang, P. D. Imaging Single ZnO Vertical Nanowire Laser Cavities Using UV-Laser Scanning Confocal Microscopy. J. Am. Chem. Soc. 2009, 131, 2125−2127. (11) Li, Y.; Zhang, J.; Huang, D.; Sun, H.; Fan, F.; Feng, J.; Wang, Z.; Ning, C. Z. Room-Temperature Continuous-Wave Lasing from Monolayer Molybdenum Ditelluride Integrated with a Silicon Nanobeam Cavity. Nat. Nanotechnol. 2017, 12, 987−992. (12) Yang, Z.; Pelton, M.; Fedin, I.; Talapin, D. V.; Waks, E. A Room Temperature Continuous-Wave Nanolaser Using Colloidal Quantum Wells. Nat. Commun. 2017, 8, 143. (13) Zhang, F.; Zhong, H.; Chen, C.; Wu, X. G.; Hu, X.; Huang, H.; Han, J.; Zou, B.; Dong, Y. Brightly Luminescent and Color-Tunable
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jpclett.9b00658. Description of the in situ fabrication of PQD-embedded PAN films, time-resolved lifetime measurement, DFB cavity design and fabrication, density functional theory calculations, thermal conductivities of commercial polymers, TEM image of MAPbBr3 PQDs in a PAN matrix, temperature-dependent PL spectra of the MAPbBr3 PQD-embedded PAN film, time-resolved PL traces of the film at temperatures ranging from 200 to 400 K, setup of the polarized lasing measurement, 3252
DOI: 10.1021/acs.jpclett.9b00658 J. Phys. Chem. Lett. 2019, 10, 3248−3253
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The Journal of Physical Chemistry Letters
Revealed by Two-dimensional Electronic Spectroscopy. J. Phys. Chem. Lett. 2019, 10, 1251−1258. (31) Cadelano, M.; Sarritzu, V.; Sestu, N.; Marongiu, D.; Chen, F.; Piras, R.; Corpino, R.; Carbonaro, C. M.; Quochi, F.; Saba, M.; Mura, A.; Bongiovanni, G. Can Trihalide Lead Perovskites Support Continuous Wave Lasing? Adv. Opt. Mater. 2015, 3, 1557−1564. (32) Zhou, Q.; Bai, Z.; Lu, W. G.; Wang, Y.; Zou, B.; Zhong, H. In Situ Fabrication of Halide Perovskite Nanocrystal-Embedded Polymer Composite Films with Enhanced Photoluminescence for Display Backlights. Adv. Mater. 2016, 28, 9163−9168. (33) Wang, Y.; He, J.; Chen, H.; Chen, J.; Zhu, R.; Ma, P.; Towers, A.; Lin, Y.; Gesquiere, A. J.; Wu, S. T.; Dong, Y. Ultrastable, Highly Luminescent Organic-Inorganic Perovskite-Polymer Composite Films. Adv. Mater. 2016, 28, 10710−10717. (34) Klimov, V. I.; Ivanov, S. A.; Nanda, J.; Achermann, M.; Bezel, I.; McGuire, J. A.; Piryatinski, A. Single-Exciton Optical Gain in Semiconductor Nanocrystals. Nature 2007, 447, 441−446. (35) Gao, Y.; Peng, X. Photogenerated Excitons in Plain Core CdSe Nanocrystals with Unity Radiative Decay in Single Channel: The Effects of Surface and Ligands. J. Am. Chem. Soc. 2015, 137, 4230− 4235. (36) Zhou, J.; Zhu, M.; Meng, R.; Qin, H.; Peng, X. Ideal CdSe/CdS Core/Shell Nanocrystals Enabled by Entropic Ligands and Their Core Size-, Shell Thickness-, and Ligand-Dependent Photoluminescence Properties. J. Am. Chem. Soc. 2017, 139, 16556−16567. (37) Adachi, M. M.; Fan, F.; Sellan, D. P.; Hoogland, S.; Voznyy, O.; Houtepen, A. J.; Parrish, K. D.; Kanjanaboos, P.; Malen, J. A.; Sargent, E. H. Microsecond-Sustained Lasing from Colloidal Quantum Dot Solids. Nat. Commun. 2015, 6, 8694. (38) Han, Z.; Fina, A. Thermal Conductivity of Carbon Nanotubes and Their Polymer Nanocomposites: A Review. Prog. Polym. Sci. 2011, 36, 914−944. (39) Chen, H.; Ginzburg, V. V.; Yang, J.; Yang, Y.; Liu, W.; Huang, Y.; Du, L.; Chen, B. Thermal Conductivity of Polymer-Based Composites: Fundamentals and Applications. Prog. Polym. Sci. 2016, 59, 41−85. (40) Kalyuzhny, G.; Murray, R. W. Ligand Effects on Optical Properties of CdSe Nanocrystals. J. Phys. Chem. B 2005, 109, 7012− 7021. (41) Castaneda, J. A.; Nagamine, G.; Yassitepe, E.; Bonato, L. G.; Voznyy, O.; Hoogland, S.; Nogueira, A. F.; Sargent, E. H.; Cruz, C. H.; Padilha, L. A. Efficient Biexciton Interaction in Perovskite Quantum Dots Under Weak and Strong Confinement. ACS Nano 2016, 10, 8603−8609. (42) Yarita, N.; Tahara, H.; Ihara, T.; Kawawaki, T.; Sato, R.; Saruyama, M.; Teranishi, T.; Kanemitsu, Y. Dynamics of Charged Excitons and Biexcitons in CsPbBr3 Perovskite Nanocrystals Revealed by Femtosecond Transient-Absorption and Single-Dot Luminescence Spectroscopy. J. Phys. Chem. Lett. 2017, 8, 1413−1418. (43) Huang, H.; Zhao, F.; Liu, L.; Zhang, F.; Wu, X. G.; Shi, L.; Zou, B.; Pei, Q.; Zhong, H. Emulsion Synthesis of Size-Tunable CH3NH3PbBr3 Quantum Dots: An Alternative Route toward Efficient Light-Emitting Diodes. ACS Appl. Mater. Interfaces 2015, 7, 28128− 28133. (44) Yumoto, G.; Tahara, H.; Kawawaki, T.; Saruyama, M.; Sato, R.; Teranishi, T.; Kanemitsu, Y. Hot Biexciton Effect on Optical Gain in CsPbI3 Perovskite Nanocrystals. J. Phys. Chem. Lett. 2018, 9, 2222− 2228. (45) Jia, W.; Cao, Z.; Wang, L.; Fu, J.; Chi, X.; Gao, W.; Wang, L. W. The Analysis of A Plane Wave Pseudopotential Density Functional Theory Code on A GPU Machine. Comput. Phys. Commun. 2013, 184, 9−18. (46) Jia, W.; Fu, J.; Cao, Z.; Wang, L.; Chi, X.; Gao, W.; Wang, L. W. Fast Plane Wave Density Functional Theory Molecular Dynamics Calculations on Multi-GPU Machines. J. Comput. Phys. 2013, 251, 102−115.
Colloidal CH3NH3PbX3 (X = Br, I, Cl) Quantum Dots: Potential Alternatives for Display Technology. ACS Nano 2015, 9, 4533−4542. (14) Kovalenko, M. V.; Protesescu, L.; Bodnarchuk, M. I. Properties and Potential Optoelectronic Applications of Lead Halide Perovskite Nanocrystals. Science 2017, 358, 745−750. (15) Yu, D.; Cao, F.; Shen, Y.; Liu, X.; Zhu, Y.; Zeng, H. Dimensionality and Interface Engineering of 2D Homologous Perovskites for Boosted Charge-Carrier Transport and Photodetection Performances. J. Phys. Chem. Lett. 2017, 8, 2565−2572. (16) Jia, Y.; Kerner, R. A.; Grede, A. J.; Rand, B. P.; Giebink, N. C. Continuous-Wave Lasing in an Organic−Inorganic Lead Halide Perovskite Semiconductor. Nat. Photonics 2017, 11, 784−788. (17) Li, Z.; Moon, J.; Gharajeh, A.; Haroldson, R.; Hawkins, R.; Hu, W.; Zakhidov, A. A.; Gu, Q. Room-Temperature Continuous-Wave Operation of Organometal Halide Perovskite Lasers. ACS Nano 2018, 12, 10968−10976. (18) Jia, Y.; Kerner, R. A.; Grede, A. J.; Brigeman, A. N.; Rand, B. P.; Giebink, N. C. Diode-Pumped Organo-Lead Halide Perovskite Lasing in a Metal-Clad Distributed Feedback Resonator. Nano Lett. 2016, 16, 4624−4629. (19) Eaton, S. W.; Lai, M.; Gibson, N. A.; Wong, A. B.; Dou, L.; Ma, J.; Wang, L. W.; Leone, S. R.; Yang, P. Lasing in Robust Cesium Lead Halide Perovskite Nanowires. Proc. Natl. Acad. Sci. U. S. A. 2016, 113, 1993−1998. (20) Evans, T. J. S.; Schlaus, A.; Fu, Y.; Zhong, X.; Atallah, T. L.; Spencer, M. S.; Brus, L. E.; Jin, S.; Zhu, X. Y. Continuous-Wave Lasing in Cesium Lead Bromide Perovskite Nanowires. Adv. Opt. Mater. 2018, 6, 1700982. (21) Liao, Q.; Hu, K.; Zhang, H.; Wang, X.; Yao, J.; Fu, H. Perovskite Microdisk Microlasers Self-Assembled from Solution. Adv. Mater. 2015, 27, 3405−3410. (22) Wang, Y.; Li, X.; Song, J.; Xiao, L.; Zeng, H.; Sun, H. AllInorganic Colloidal Perovskite Quantum Dots: A New Class of Lasing Materials with Favorable Characteristics. Adv. Mater. 2015, 27, 7101− 7108. (23) Xing, G.; Mathews, N.; Lim, S. S.; Yantara, N.; Liu, X.; Sabba, D.; Gratzel, M.; Mhaisalkar, S.; Sum, T. C. Low-Temperature Solution-Processed Wavelength-Tunable Perovskites for Lasing. Nat. Mater. 2014, 13, 476−480. (24) Xing, J.; Liu, X. F.; Zhang, Q.; Ha, S. T.; Yuan, Y. W.; Shen, C.; Sum, T. C.; Xiong, Q. Vapor Phase Synthesis of Organometal Halide Perovskite Nanowires for Tunable Room-Temperature Nanolasers. Nano Lett. 2015, 15, 4571−4577. (25) Xu, Y.; Chen, Q.; Zhang, C.; Wang, R.; Wu, H.; Zhang, X.; Xing, G.; Yu, W. W.; Wang, X.; Zhang, Y.; Xiao, M. Two-PhotonPumped Perovskite Semiconductor Nanocrystal Lasers. J. Am. Chem. Soc. 2016, 138, 3761−3768. (26) Zhu, H.; Fu, Y.; Meng, F.; Wu, X.; Gong, Z.; Ding, Q.; Gustafsson, M. V.; Trinh, M. T.; Jin, S.; Zhu, X. Y. Lead Halide Perovskite Nanowire Lasers With Low Lasing Thresholds and High Quality Factors. Nat. Mater. 2015, 14, 636−642. (27) Pushkarev, A.; Korolev, V.; Markina, D.; Komissarenko, F.; Naujokaitis, A.; Drabavicius, A.; Pakstas, V.; Franckevicius, M.; Khubezhov, S.; Sannikov, D.; Zasedatelev, A.; Lagoudakis, P.; Zakhidov, A. A.; Makarov, S. V. A Few-Minute Synthesis of CsPbBr3 Nanolasers with a High Quality Factor by Spraying at Ambient Conditions. ACS Appl. Mater. Interfaces 2019, 11, 1040−1048. (28) Deschler, F.; Price, M.; Pathak, S.; Klintberg, L. E.; Jarausch, D. D.; Higler, R.; Huttner, S.; Leijtens, T.; Stranks, S. D.; Snaith, H. J.; Atature, M.; Phillips, R. T.; Friend, R. H. High Photoluminescence Efficiency and Optically Pumped Lasing in Solution-Processed Mixed Halide Perovskite Semiconductors. J. Phys. Chem. Lett. 2014, 5, 1421−1426. (29) Nagamine, G.; Rocha, J. O.; Bonato, L. G.; Nogueira, A. F.; Zaharieva, Z.; Watt, A. A. R.; de Brito Cruz, C. H.; Padilha, L. A. Two-Photon Absorption and Two-Photon-Induced Gain in Perovskite Quantum Dots. J. Phys. Chem. Lett. 2018, 9, 3478−3484. (30) Zhao, W.; Qin, Z.; Zhang, C.; Wang, G.; Huang, X.; Li, B.; Dai, X.; Xiao, M. Optical Gain from Biexcitons in CsPbBr3 Nanocrystals 3253
DOI: 10.1021/acs.jpclett.9b00658 J. Phys. Chem. Lett. 2019, 10, 3248−3253
