Manipulating Ion Migration for Highly Stable Light-Emitting Diodes with Single-Crystalline Organometal Halide Perovskite Microplatelets Mingming Chen,†,§ Xin Shan,† Thomas Geske,†,‡ Junqiang Li,† and Zhibin Yu*,†,‡ †
Department of Industrial and Manufacturing Engineering, High-Performance Materials Institute, FAMU-FSU College of Engineering, Florida State University, Tallahassee, Florida 32310, United States ‡ Materials Science and Engineering, Florida State University, Tallahassee, Florida 32306, United States § Faculty of Science, Jiangsu University, Zhenjiang, Jiangsu 212013, China S Supporting Information *
ABSTRACT: Ion migration has been commonly observed as a detrimental phenomenon in organometal halide perovskite semiconductors, causing the measurement hysteresis in solar cells and ultrashort operation lifetimes in light-emitting diodes. In this work, ion migration is utilized for the formation of a p-i-n junction at ambient temperature in single-crystalline organometal halide perovskites. The junction is subsequently stabilized by quenching the ionic movement at a low temperature. Such a strategy of manipulating the ion migration has led to efficient singlecrystalline light-emitting diodes that emit 2.3 eV photons starting at 1.8 V and sustain a continuous operation for 54 h at ∼5000 cd m−2 without degradation of brightness. In addition, a whispering-gallery-mode cavity and exciton−exciton interaction in the perovskite microplatelets have both been observed that can be potentially useful for achieving electrically driven laser diodes based on single-crystalline organometal halide perovskite semiconductors. KEYWORDS: halide perovskites, microplatelets, light-emitting diodes, ion migration, laser, single crystal
O
perovskite emitter is an essential step toward achieving electrically driven laser diodes. To date, a number of research groups have reported the synthesis of single-crystalline perovskite microplatelets and nanowires11,26−28 and have demonstrated optically pumped laser generation at a low lasing threshold;11,26,29 however, no EL devices have been realized. One major challenge is the use of a multilayered device architecture in most OHP LEDs, which requires at least an electron injection layer (EIL), a hole injection layer (HIL), and an emissive perovskite layer in addition to the cathode and anode.12,19 Such a multilayered device structure cannot be easily replicated on micro- or nanometer size perovskite single crystals. In this work, we report OHP LEDs using single-crystalline methylammonium lead tribromide (MAPbBr3) microplatelets. The LEDs were fabricated without using any EILs or HILs. The device configuration consisted of an indium tin oxide (ITO) anode, a single-crystalline MAPbBr3 microplatelet emissive
rganometal halide perovskites (OHPs) have attracted much attention in recent years owing to their remarkable electro-optical properties and good solubility in certain organic solvents, potentially enabling a variety of large-area and low-cost electronic devices.1−3 The power conversion efficiencies of OHP solar cells have increased rapidly from 3.8% to more than 20% within the past few years.4−7 It has also been observed that OHPs exhibit exceptional photoluminescence efficiency, weak Auger recombination, and high color purity,8−11 making them ideal emitter materials for light-emitting diodes (LEDs) and laser diodes. OHP LEDs were first demonstrated by Tan et al. in 2014,12 and the current state-of-the-art devices have obtained a maximum luminance of 591 197 cd m−2 with a power efficiency of 14.1 lm W−1.13−16 Noticeably, all reported OHP LEDs have employed an emissive layer consisting of polycrystalline or amorphous perovskites with average domain sizes of a few micrometers to a few nanometers.12−25 Thus, coherent light emission is challenging due to the random orientations of the constituent perovskite domains. In this regard, to explore electroluminescent (EL) devices using a single-crystalline © 2017 American Chemical Society
Received: April 15, 2017 Accepted: May 17, 2017 Published: May 17, 2017 6312
DOI: 10.1021/acsnano.7b02629 ACS Nano 2017, 11, 6312−6318
Article
www.acsnano.org
Article
ACS Nano
MAPbBr3 microplatelets. The crystals appeared highly textured with two dominant peaks at 14.92 and 30.12°, corresponding to (100) and (200) of the cubic phase MAPbBr3, respectively. The lattice constant was calculated as 5.98 Å, which is consistent with reported values in literature.30 The ambient temperature photoluminescence (PL) spectra at various excitation intensities are shown in Figure 1c. All the spectra exhibit one main peak centered at 543 nm and a shoulder peak at 563 nm wavelength. It is observed that the relative intensity of the shoulder peak is enhanced with increasing excitation power. Such a nonlinear emission behavior agrees well with the recent report by Kunugita et al., attributing the shoulder peak to the exciton−exciton scattering process in the perovskite crystals.31 After preparing the microplatelet crystals, we proceeded to fabricate single-crystalline MAPbBr3 LEDs. The device structure is schematically shown in Figure S2: ITO on glass was used as the anode; a MAPbBr3 microplatelet was used as the active light-emitting media, and a 5 nm Au film was sputtered and used as the cathode. One Au wire of 12.5 μm diameter was mounted onto a micromanipulator and brought in contact with the crystal top surface. An optical microscope integrated with a digital camera and a spectrometer was used to record the light emission characteristics of the LEDs. A microscopic optical image of a complete device at 0 V is shown in Figure S3a. Figure 2a shows the current−voltage (I−V) characteristics of one microplatelet LED measured at ambient temperature. The current had a rapid increase at low voltages, followed by a gradual growth after 5 V and turned to saturate after 15 V. Light emission was clearly visible from the LEDs at 3 V (Figure S3b). It is interesting to note that the light emission was not uniform, likely caused by a waveguide effect of the perovskite microplatelet: at 3 V bias, a light spot was seen close to one edge of the sample. At 8 V bias, an intense light spot appeared around the center of the microplatelet, accompanied by noticeable light emission from the middle of the side surfaces (Figure S3c). At 18 V, the emission intensified in the center region, and light emission from the middle of all the four side surfaces became quite bright (Figure S3d). Such a periodic emission pattern can be caused by a whispering-gallery-mode (WGM) cavity that is formed by the four side faces of the microplatelet.32 It is worth mentioning our devices did not employ any EILs or HILs. The relative energy-level diagram of ITO, perovskite, and Au is schematically drawn in Figure S4. Very large energy offsets are identified between the ITO anode and the valence band maximum of the perovskite (1.0 eV) and between the Au cathode and the perovskite’s conduction band minimum (1.7 eV), respectively.33 It was postulated that ionic migration under an external electrical field led to the formation of a p-i-n junction in the single-crystalline perovskite emitter: the perovskite became n-doped next to the cathode and p-doped next to the anode.34 The doping facilitates interfacial band bending between the electrodes and the perovskite emissive layer, thus lowering the energy barriers for electron and hole injection.15,35,36 While it still remains unclear what ionic species (the cation, anion, and/or complex ions) contribute to such an ion migration process,37−41 recent studies by Shao et al.42 and by Yun et al.43 provided important insights on the migration pathways of such ions: it was discovered the ions predominantly migrated along grain boundaries in polycrystalline perovskites. In another study, Dong et al. observed the formation of a p-i-n junction on the surface of a singlecrystalline halide perovskite under a lateral electrical field,44
layer, and a gold (Au) cathode. Despite the large energy barriers between the electrodes and the MAPbBr3, EL was observed at a low applied voltage at ambient temperature. We hypothesize the in situ formation of a p-i-n junction through electrical-field-induced migration of cations and/or anions within the perovskite microplatelets. Such a junction was found to disappear within a few minutes at ambient temperature when the external voltage was removed. However, by quenching the device to a low temperature with an applied voltage, the ion migration was inhibited, and the in situ formed junction was stabilized. This leads to efficient and highly stable OHP LEDs that turned on at 1.8 V and continuously lit at ∼5000 cd m−2 for 54 h without degradation.
RESULTS AND DISCUSSION The single-crystalline MAPbBr3 microplatelets were synthesized following a literature procedure.28 Figure 1a and Figure
Figure 1. (a) SEM image, (b) XRD, and (c) normalized PL spectra of the MAPbBr3 microplatelets.
S1 show typical scanning electron microscope (SEM) images of the obtained perovskite crystals. The platelets had square or rectangular shapes with very smooth top surfaces and sharp edges. The lateral dimensions of most platelets fell within 20− 100 μm, and they had a typical thickness of ∼10 μm. Figure 1b shows the X-ray diffraction (XRD) pattern of obtained 6313
DOI: 10.1021/acsnano.7b02629 ACS Nano 2017, 11, 6312−6318
Article
ACS Nano
voltage (Voc) were both negligible (Figure 2b, black and red curves) due to the large energy barriers along the electrode/ perovskite interfaces that diminished charge carrier collection efficiency under photoexcitation. The same device was then subjected to a 10 V bias for 1 min. I−V characteristics were measured again, as shown in Figure 2b (blue and green curves). An Isc of 5.6 nA and a Voc of 0.9 V were obtained under light irradiation, in agreement with the junction formation hypothesis after the 10 V biasing. Isc was also monitored over time with a pulsed light illumination, as shown in Figure 2c. After the 10 V biasing, the Isc showed a decreasing tendency with time, indicating the disappearing of the junction was likely due to relaxation of the previously accumulated ions through a thermal diffusion process toward their equilibrium positions at a zero bias. The diffusivity of ions in OHPs is expected to decrease with decreasing temperature; therefore, the ions can be immobilized below a certain temperature. In one experiment, a pristine microplatelet crystal was cooled to liquid nitrogen temperature (−193 °C), and the I−V characteristics were measured as shown in Figure S5. Noticeably, the device exhibited a much smaller current compared with the same measurement at ambient temperature, and no light emission was observed at 6 V. Thus, it is conjectured that the in situ formed junction at ambient temperature can be stabilized at a low temperature by eliminating the thermal movement and relaxation of ions after formation of the junction. Such an approach has been previously applied to realize “frozen junction” polymer lightemitting electrochemical cells with success.45,46 To test such a hypothesis in OHPs, an LED was biased with 6 V at ambient temperature. The bias was maintained while the device was cooled to −193 °C at 60 °C min−1. The bias was then removed after the temperature reached −193 °C. Photocurrent responses were measured under a pulsed light illumination, as shown in Figure 3a. In contrast to the result shown in Figure 2c, a nearly constant Isc was observed over time, proving the junction was preserved even after the bias was removed at −193 °C. A slight decay of photocurrent started to appear when the temperature was elevated to −110 °C (Figure 3b). More substantial photocurrent decay took place at −50 and −10 °C, as shown in Figure 3c,d, respectively. The above results indicate that the junction formed at ambient temperature can be frozen by lowering the temperature below −110 °C. The I−V characteristics of the perovskite LEDs with a frozen junction were measured at −193 °C, as shown in Figure S6a. Very little hysteresis was observed. In contrast, significant hysteresis was seen when the device was measured at ambient temperature. The photocurrent evolution over time in Figure 2c and Figure 3d,c was reproduced in Figure S7a−c, respectively. The relative photocurrent decay (ΔI/I0) can be well fitted using an exponential eq 1, where I0 and I are the photocurrents at t = 0 and at a specified time t, respectively; τ is a time constant correlates to the mobile ions relaxation processes back to their equilibrium positions after removing the bias.
Figure 2. (a) I−V characteristics of one representative MAPbBr3 microplatelet LED at ambient temperature. (b) I−V characteristics of one LED measured with (light) and without (dark) light irradiation before and after electrical biasing. The electrical biasing was carried out at 10 V for 1 min. (c) Photocurrent (at V = 0) responses of a pristine and a prebiased device under a pulsed light illumination.
demonstrating the ions can also migrate along the surfaces of perovskite single crystals. In this work, we obtained light emission at 3 V for our microplatelet OHP LEDs with an emissive layer thickness of ∼10 μm. This result suggests ions can also migrate through single-crystalline perovskites under an external electrical field as low as 0.3 V μm−1 to form a vertical p-i-n junction that is demanded for efficient charge carrier injection and EL in our OHP LEDs. The formation of a vertical p-i-n junction in the microplatelet OHP LEDs was further supported by photocurrent response measurements as shown in Figure 2b,c. The I−V characteristics were collected for one pristine LED device by sweeping the voltage from 0 to 1 V while keeping the device in the dark or under a white light (xenon lamp, 25 mW cm−2) illumination. The photogenerated short-circuit current (Isc) and open-circuit
⎡ I −I ⎛ − t ⎞⎤ ΔI = 0 ∝ ⎢1 − exp⎜ ⎟⎥ ⎝ τ ⎠⎦ ⎣ I0 I0
(1)
The value of τ was obtained as 46.2, 77.6, and 573.5 s at 25, −10, and −50 °C, respectively. According to the Arrhenius formula, eq 2 is valid where ΔE represents the activation energy for ion migration processes, k is the Boltzmann constant, and T is the temperature. 6314
DOI: 10.1021/acsnano.7b02629 ACS Nano 2017, 11, 6312−6318
Article
ACS Nano
Figure 3. Photocurrent (at V = 0) responses from the MAPbBr3 microplatelet LEDs under a pulsed light illumination at different temperatures: (a) −193 °C, (b) −110 °C, (c) −50 °C, and (d) −10 °C. Before the measurements, the LEDs were prebiased at 6 V at ambient temperature, cooled to −193 °C, and the bias was removed.
Figure 4. (a) I−V characteristics of an LED with a frozen junction. The LED was prebiased at 6 V at ambient temperature, cooled to −193 °C, and the bias was removed before the measurement (inset: a microscopic optical image of the LED at 0 V). (b) Electroluminescence spectra of the frozen junction LED at different applied voltages. (c−g) Microscopic optical images of the LEDs at different applied voltages.
ln τ −1 ∝
ΔE kT
their experimental findings and agrees well with the theoretical simulation that bromide ions dominate the ion migration processes in MAPbBr3. Single-crystalline OHP LEDs with a frozen junction were also characterized. The device structure follows the one used in Figure 2a. The device was biased at 6 V at ambient temperature, then cooled to −193 °C, and the bias was removed. A microscopic optical image of such a device is shown in the inset of Figure 4a. I−V characteristics, emission spectra, and representative optical images of the LED at different voltages
(2)
The plot of ln τ−1 vs T−1 is shown in Figure S7d. An activation energy of 0.197 ± 0.042 eV is calculated from the slope of the linear fitting line. It is worth noting that Meloni et al. have experimentally measured an activation energy of 0.168 ± 0.043 eV for ion migration processes in MAPbBr3.41 Moreover, they obtained 0.2−0.28 eV in their theoretical simulation by assuming a mechanism of vacancy-assisted migration of bromide anions. Our measurement here confirms 6315
DOI: 10.1021/acsnano.7b02629 ACS Nano 2017, 11, 6312−6318
Article
ACS Nano
after the stress test started, demonstrating the intense and steady green light emission from the LED. In contrast, the LEDs showed flickering emission, and each flickering lasted for tens of seconds when they were tested at ambient temperature (supporting video and Figure S10), suggesting the instability of the in situ formed junction at this temperature due to continuous migration of the ions. Such an observation signifies the importance of immobilizing the ions after the junction formation for achieving stable and long-lasting OHP electroluminescent devices.
are shown in Figure 4a−g. Light emission was detected at 1.8 V (Figure S8), which had largely shifted toward lower voltages when compared with control devices measured at ambient temperature. The turn-on voltage of ∼1.8 V is 0.5 V lower than the band gap (Eg, 2.3 eV)/e of the MAPbBr3. Such results suggest that the frozen junction at low temperature works very efficiently to assist electron and hole injection into the OHP microplatelet crystals. The measured light-emitting intensity increased with the applied voltage until 3.6 V but decreased at 4.0 V (Figure 4b) likely due to a reduced efficiency of light collection in our current measurement setup as more and more photons emitted from the side surfaces (Figure 4e−g). Two peaks can be identified in all the EL spectra in Figure 4b, one at 542−544 nm and the second at 548−551 nm, attributed to the same exciton−exciton scattering process as discussed for Figure 1c. The relative intensity of the 548−551 nm peak (Figure S9) was enhanced with increasing voltage after 2.4 V, indicating the exciton−exciton scattering process had become more significant at a high injection current density. Such a tendency correlates well with the PL evolution with different excitation light intensities, as shown in Figure 1c. A slight red-shifting trend was also observed for the second emission peak after 2.8 V, due to enhanced exciton−exciton scattering at a high exciton density.47 It is worth mentioning that exciton−exciton scattering has been used as a mechanism to realize stimulated light emission at a low excitation threshold in zinc oxide semiconductor thin films.48,49 Therefore, our LED result in this work could be further optimized in the future to achieve electrically driven excitonic laser based on solutionprocessed OHPs. Finally, the stability of the OHP LEDs with a frozen junction was examined through a stress test with a constant current (1 mA) at −193 °C. The light-emitting intensity was monitored by a silicon photodiode. A starting luminance of ∼5000 cd m−2 was estimated from the measured photocurrent, corresponding to a current efficient of 0.05 cd A−1. These values are underestimated as the photons escaping from the side surfaces were not collected by the photodiode. As shown in Figure 5,
CONCLUSION We demonstrated single-crystalline OHP LEDs with an ITO anode, MAPbBr3 microplatelet emitter, and Au cathode. It was discovered that ion migration could occur through the OHP microplatelets at ambient temperature upon applying a relatively low electrical field (∼0.3 V μm−1). A light-emitting junction was formed, which decayed at ambient temperature after removing the external electrical field. The junction was stabilized by lowering the temperature below −110 °C to freeze the ionic movement and eliminate their thermally activated relaxation processes. As a result, efficient and stable LEDs have been achieved that turned on at 1.8 V and lasted for at least 54 h with a luminance of ∼5000 cd m−2 without degradation. Although the ultralong lifetime is achieved at a cryogenic temperature, the work provides insight on manipulating ion migration with more practical approaches for future generation OHP LEDs. In addition, the WGM cavity formed by the smooth outer surfaces and sharp edges and the exciton−exciton interaction in the MAPbBr3 microplatelets can be potentially useful for achieving electrically driven laser diodes based on OHP semiconductors. EXPERIMENTAL SECTION Materials. Lead(II) bromide (99.999%), dichloromethane (anhydrous, 99.8%) and N,N-dimethylformamide (anhydrous, 99.8%) were purchased from Sigma-Aldrich. The methylammonium bromide was purchased from 1-Material Inc. All materials were used as received. MAPbBr3 Microplatelet Synthesis and Characterizations. The MAPbBr3/DMF precursor solution was prepared by dissolving PbBr2 and CH3NH3Br with a 1:1.5 molar ratio in anhydrous DMF to give a molar concentration of 0.02 M. The ITO/glass substrates (20 Ω sq−1) were cleaned subsequently with acetone, isopropyl alcohol, and DI water and then treated with oxygen plasma for 2 min (FEMTO SCIENCE CUTE-MPR, oxygen flow 50 sccm, power 50 W). The substrates were placed in a Teflon beaker containing 200 μL of MAPbBr3/DMF precursor solution. The Teflon was placed in a glass beaker containing 3 mL of DCM, which was then sealed by Parafilm and kept for 24 h at ambient temperature. SEM images of assynthesized microplatelets were acquired using a field emission SEM (JEOL 7401F). The acceleration voltage was set at 10 kV. Powder XRD patterns were recorded using an XRD (X’PERT Pro MPD) equipped with Cu Kα radiation source. PL was measured using a 488 nm excitation laser using a confocal Raman system (Renishaw). LED Characterizations. Current−voltage characteristics were measured using a Keithley 2410 source measure unit. The LEDs were tested under a nitrogen atmosphere inside a Linkam THMS600 cold/hot stage. The EL spectra were recorded using the same Raman system as PL measurement.
Figure 5. Relative light emission intensity vs time of an LED operated at a constant 1 mA current at −193 °C. The LED had a starting luminance of ∼5000 cd m−2. Inset shows a microscopic image of the LED at t = 12 h.
the luminance decreased to about 92% of the starting value after about 2 h. Interestingly, the trend then reversed, and the light intensity obtained a maximum of 115% after 40 h and maintained 112% of the starting intensity after 54 h, respectively. A microscopic image in the inset of Figure 5 and a video in the Supporting Information were taken at 12 h
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsnano.7b02629. Supplemental figures (PDF) 6316
DOI: 10.1021/acsnano.7b02629 ACS Nano 2017, 11, 6312−6318
Article
ACS Nano
Emitting Diodes Based on Organometal Halide Perovskite. Nat. Nanotechnol. 2014, 9, 687−692. (13) Chih, Y.-K.; Wang, J.-C.; Yang, R.-T.; Liu, C.-C.; Chang, Y.-C.; Fu, Y.-S.; Lai, W.-C.; Chen, P.; Wen, T.-C.; Huang, Y.-C.; Tsao, C.-S.; Guo, T.-F. NiOx Electrode Interlayer and CH3NH2/CH3NH3PbBr3 Interface Treatment to Markedly Advance Hybrid Perovskite-Based Light-Emitting Diodes. Adv. Mater. 2016, 28, 8687−8694. (14) Cho, H.; Jeong, S.-H.; Park, M.-H.; Kim, Y.-H.; Wolf, C.; Lee, C.-L.; Heo, J. H.; Sadhanala, A.; Myoung, N.; Yoo, S.; Im, S. H.; Friend, R. H.; Lee, T.-W. Overcoming the Electroluminescence Efficiency Limitations of Perovskite Light-Emitting Diodes. Science 2015, 350, 1222−1225. (15) Li, J.; Shan, X.; Bade, S. G. R.; Geske, T.; Jiang, Q.; Yang, X.; Yu, Z. Single-Layer Halide Perovskite Light-Emitting Diodes with SubBand Gap Turn-On Voltage and High Brightness. J. Phys. Chem. Lett. 2016, 7, 4059−4066. (16) Ling, Y.; Tian, Y.; Wang, X.; Wang, J. C.; Knox, J. M.; PerezOrive, F.; Du, Y.; Tan, L.; Hanson, K.; Ma, B.; Gao, H. Enhanced Optical and Electrical Properties of Polymer-Assisted All-Inorganic Perovskites for Light-Emitting Diodes. Adv. Mater. 2016, 28, 8983− 8989. (17) Huang, H.; Zhao, F.; Liu, L.; Zhang, F.; Wu, X.; 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. (18) Song, J.; Li, J.; Li, X.; Xu, L.; Dong, Y.; Zeng, H. Quantum Dot Light-Emitting Diodes Based on Inorganic Perovskite Cesium Lead Halides (CsPbX3). Adv. Mater. 2015, 27, 7162−7167. (19) Wang, J.; Wang, N.; Jin, Y.; Si, J.; Tan, Z.-K.; Du, H.; Cheng, L.; Dai, X.; Bai, S.; He, H.; Ye, Z.; Lai, M. L.; Friend, R. H.; Huang, W. Interfacial Control Toward Efficient and Low-Voltage Perovskite Light-Emitting Diodes. Adv. Mater. 2015, 27, 2311−2316. (20) Xing, J.; Yan, F.; Zhao, Y.; Chen, S.; Yu, H.; Zhang, Q.; Zeng, R.; Demir, H. V.; Sun, X.; Huan, A.; Xiong, Q. High-Efficiency LightEmitting Diodes of Organometal Halide Perovskite Amorphous Nanoparticles. ACS Nano 2016, 10, 6623−6630. (21) Zhang, X.; Lin, H.; Huang, H.; Reckmeier, C.; Zhang, Y.; Choy, W. C. H.; Rogach, A. L. Enhancing the Brightness of Cesium Lead Halide Perovskite Nanocrystal Based Green Light-Emitting Devices through the Interface Engineering with Perfluorinated Ionomer. Nano Lett. 2016, 16, 1415−1420. (22) Kim, Y.-H.; Cho, H.; Lee, T.-W. Metal Halide Perovskite Light Emitters. Proc. Natl. Acad. Sci. U. S. A. 2016, 113, 11694−11702. (23) Kim, Y.-H.; Cho, H.; Heo, J. H.; Kim, T.-S.; Myoung, N.; Lee, C.-L.; Im, S. H.; Lee, T.-W. Multicolored Organic/Inorganic Hybrid Perovskite Light-Emitting Diodes. Adv. Mater. 2015, 27, 1248−1254. (24) Byun, J.; Cho, H.; Wolf, C.; Jang, M.; Sadhanala, A.; Friend, R. H.; Yang, H.; Lee, T.-W. Efficient Visible Quasi-2D Perovskite LightEmitting Diodes. Adv. Mater. 2016, 28, 7515−7520. (25) Seo, H.-K.; Kim, H.; Lee, J.; Park, M.-H.; Jeong, S.-H.; Kim, Y.H.; Kwon, S.-J.; Han, T.-H.; Yoo, S.; Lee, T.-W. Efficient Flexible Organic/Inorganic Hybrid Perovskite Light-Emitting Diodes Based on Graphene Anode. Adv. Mater. 2017, 29, 1605587. (26) 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. (27) Ha, S. T.; Liu, X.; Zhang, Q.; Giovanni, D.; Sum, T. C.; Xiong, Q. Synthesis of Organic−Inorganic Lead Halide Perovskite Nanoplatelets: Towards High-Performance Perovskite Solar Cells and Optoelectronic Devices. Adv. Opt. Mater. 2014, 2, 838−844. (28) 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. (29) Zhang, Q.; Ha, S. T.; Liu, X.; Sum, T. C.; Xiong, Q. RoomTemperature Near-Infrared High-Q Perovskite Whispering-Gallery Planar Nanolasers. Nano Lett. 2014, 14, 5995−6001. (30) Shi, D.; Adinolfi, V.; Comin, R.; Yuan, M.; Alarousu, E.; Buin, A.; Chen, Y.; Hoogland, S.; Rothenberger, A.; Katsiev, K.; Losovyj, Y.;
Videos of LEDs at room temperature and at liquid nitrogen temperature (ZIP)
AUTHOR INFORMATION Corresponding Author
*E-mail:
[email protected]. ORCID
Zhibin Yu: 0000-0002-4630-4363 Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS The authors are thankful for the financial support from Air Force Office of Scientific Research under Award FA9550-16-10124 and the support from National Science Foundation under Award ECCS-1609032. We thank Dr. Jin Gyu Park for assisting the PL and EL spectra collection, the Materials Characterization Laboratory of FSU for the XRD measurement, and Dr. Qinglong Jiang for technical discussions. M.C. thanks the support from China Scholarship Council (CSC) under Grant 201508320105. REFERENCES (1) Green, M. A.; Ho-Baillie, A.; Snaith, H. J. The Emergence of Perovskite Solar Cells. Nat. Photonics 2014, 8, 506−514. (2) Kazim, S.; Nazeeruddin, M. K.; Grätzel, M.; Ahmad, S. Perovskite as Light Harvester: A Game Changer in Photovoltaics. Angew. Chem., Int. Ed. 2014, 53, 2812−2824. (3) Sutherland, B. R.; Sargent, E. H. Perovskite Photonic Sources. Nat. Photonics 2016, 10, 295−302. (4) Kojima, A.; Teshima, K.; Shirai, Y.; Miyasaka, T. Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic Cells. J. Am. Chem. Soc. 2009, 131, 6050−6051. (5) Liu, M.; Johnston, M. B.; Snaith, H. J. Efficient Planar Heterojunction Perovskite Solar Cells by Vapour Deposition. Nature 2013, 501, 395−398. (6) Yang, W. S.; Noh, J. H.; Jeon, N. J.; Kim, Y. C.; Ryu, S.; Seo, J.; Seok, S. I. High-Performance Photovoltaic Perovskite Layers Fabricated through Intramolecular Exchange. Science 2015, 348, 1234−1237. (7) Zhou, H.; Chen, Q.; Li, G.; Luo, S.; Song, T.; Duan, H.-S.; Hong, Z.; You, J.; Liu, Y.; Yang, Y. Interface Engineering of Highly Efficient Perovskite Solar Cells. Science 2014, 345, 542−546. (8) Deschler, F.; Price, M.; Pathak, S.; Klintberg, L. E.; Jarausch, D.D.; Higler, R.; Hüttner, S.; Leijtens, T.; Stranks, S. D.; Snaith, H. J.; Atatüre, 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. (9) 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 with Wide Color Gamut. Nano Lett. 2015, 15, 3692−3696. (10) 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. (11) 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. (12) Tan, Z.-K.; Moghaddam, R. S.; Lai, M. L.; Docampo, P.; Higler, R.; Deschler, F.; Price, M.; Sadhanala, A.; Pazos, L. M.; Credgington, D.; Hanusch, F.; Bein, T.; Snaith, H. J.; Friend, R. H. Bright Light6317
DOI: 10.1021/acsnano.7b02629 ACS Nano 2017, 11, 6312−6318
Article
ACS Nano Zhang, X.; Dowben, P. A.; Mohammed, O. F.; Sargent, E. H.; Bakr, O. M. Low Trap-State Density and Long Carrier Diffusion in Organolead Trihalide Perovskite Single Crystals. Science 2015, 347, 519−522. (31) Kunugita, H.; Kiyota, Y.; Udagawa, Y.; Takeoka, Y.; Nakamura, Y.; Sano, J.; Matsushita, T.; Kondo, T.; Ema, K. Exciton−exciton Scattering in Perovskite CH3NH3PbBr3 Single Crystal. Jpn. J. Appl. Phys. 2016, 55, 060304. (32) Zhang, Q.; Su, R.; Liu, X.; Xing, J.; Sum, T. C.; Xiong, Q. HighQuality Whispering-Gallery-Mode Lasing from Cesium Lead Halide Perovskite Nanoplatelets. Adv. Funct. Mater. 2016, 26, 6238−6245. (33) Schulz, P.; Edri, E.; Kirmayer, S.; Hodes, G.; Cahen, D.; Kahn, A. Interface Energetics in Organo-Metal Halide Perovskite-Based Photovoltaic Cells. Energy Environ. Sci. 2014, 7, 1377−1381. (34) Xiao, Z.; Yuan, Y.; Shao, Y.; Wang, Q.; Dong, Q.; Bi, C.; Sharma, P.; Gruverman, A.; Huang, J. Giant Switchable Photovoltaic Effect in Organometal Trihalide Perovskite Devices. Nat. Mater. 2014, 14, 193−198. (35) Bade, S. G. R.; Li, J.; Shan, X.; Ling, Y.; Tian, Y.; Dilbeck, T.; Besara, T.; Geske, T.; Gao, H.; Ma, B.; Hanson, K.; Siegrist, T.; Xu, C.; Yu, Z. Fully Printed Halide Perovskite Light-Emitting Diodes with Silver Nanowire Electrodes. ACS Nano 2016, 10, 1795−1801. (36) Li, J.; Bade, S. G. R.; Shan, X.; Yu, Z. Single-Layer LightEmitting Diodes Using Organometal Halide Perovskite/Poly(ethylene Oxide) Composite Thin Films. Adv. Mater. 2015, 27, 5196−5202. (37) Eames, C.; Frost, J. M.; Barnes, P. R. F.; O’Regan, B. C.; Walsh, A.; Islam, M. S. Ionic Transport in Hybrid Lead Iodide Perovskite Solar Cells. Nat. Commun. 2015, 6, 7497. (38) Egger, D. A.; Kronik, L.; Rappe, A. M. Theory of Hydrogen Migration in Organic−Inorganic Halide Perovskites. Angew. Chem., Int. Ed. 2015, 54, 12437−12441. (39) Yuan, Y.; Chae, J.; Shao, Y.; Wang, Q.; Xiao, Z.; Centrone, A.; Huang, J. Photovoltaic Switching Mechanism in Lateral Structure Hybrid Perovskite Solar Cells. Adv. Energy Mater. 2015, 5, 1500615. (40) Calado, P.; Telford, A. M.; Bryant, D.; Li, X.; Nelson, J.; O’Regan, B. C.; Barnes, P. R. F. Evidence for Ion Migration in Hybrid Perovskite Solar Cells with Minimal Hysteresis. Nat. Commun. 2016, 7, 13831. (41) Meloni, S.; Moehl, T.; Tress, W.; Franckevičius, M.; Saliba, M.; Lee, Y. H.; Gao, P.; Nazeeruddin, M. K.; Zakeeruddin, S. M.; Rothlisberger, U.; Graetzel, M. Ionic Polarization-Induced Current− voltage Hysteresis in CH3NH3PbX3 Perovskite Solar Cells. Nat. Commun. 2016, 7, 10334. (42) Shao, Y.; Fang, Y.; Li, T.; Wang, Q.; Dong, Q.; Deng, Y.; Yuan, Y.; Wei, H.; Wang, M.; Gruverman, A.; Shield, J.; Huang, J. Grain Boundary Dominated Ion Migration in Polycrystalline Organic− inorganic Halide Perovskite Films. Energy Environ. Sci. 2016, 9, 1752− 1759. (43) Yun, J. S.; Seidel, J.; Kim, J.; Soufiani, A. M.; Huang, S.; Lau, J.; Jeon, N. J.; Seok, S. I.; Green, M. A.; Ho-Baillie, A. Critical Role of Grain Boundaries for Ion Migration in Formamidinium and Methylammonium Lead Halide Perovskite Solar Cells. Adv. Energy Mater. 2016, 6, 1600330. (44) Dong, Q.; Song, J.; Fang, Y.; Shao, Y.; Ducharme, S.; Huang, J. Lateral-Structure Single-Crystal Hybrid Perovskite Solar Cells via Piezoelectric Poling. Adv. Mater. 2016, 28, 2816−2821. (45) Gao, J.; Yu, G.; Heeger, A. J. Polymer Light-Emitting Electrochemical Cells with Frozen p-i-n Junction. Appl. Phys. Lett. 1997, 71, 1293−1295. (46) Pei, Q.; Yu, G.; Zhang, C.; Yang, Y.; Heeger, A. J. Polymer Light-Emitting Electrochemical Cells. Science 1995, 269, 1086−1088. (47) Ko, H. J.; Chen, Y. F.; Yao, T.; Miyajima, K.; Yamamoto, A.; Goto, T. Biexciton Emission from High-Quality ZnO Films Grown on Epitaxial GaN by Plasma-Assisted Molecular-Beam Epitaxy. Appl. Phys. Lett. 2000, 77, 537−539. (48) Sun, H. D.; Makino, T.; Tuan, N. T.; Segawa, Y.; Tang, Z. K.; Wong, G. K. L.; Kawasaki, M.; Ohtomo, A.; Tamura, K.; Koinuma, H. Stimulated Emission Induced by Exciton−exciton Scattering in ZnO/ ZnMgO Multiquantum Wells up to Room Temperature. Appl. Phys. Lett. 2000, 77, 4250−4252.
(49) Tang, Z. K.; Wong, G. K. L.; Yu, P.; Kawasaki, M.; Ohtomo, A.; Koinuma, H.; Segawa, Y. Room-Temperature Ultraviolet Laser Emission from Self-Assembled ZnO Microcrystallite Thin Films. Appl. Phys. Lett. 1998, 72, 3270−3272.
6318
DOI: 10.1021/acsnano.7b02629 ACS Nano 2017, 11, 6312−6318
