Supporting Information

Transcription

1 Supporting Information Morphology Evolution and Degradation of CsPbBr 3 Nanocrystals under Blue Light-Emitting Diode Illumination Shouqiang Huang, Zhichun Li, Bo Wang, Nanwen Zhu, Congyang Zhang, Long Kong, Qi Zhang, Aidang Shan, and Liang Li* School of Environmental Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, , China. liangli117@sjtu.edu.cn. Tel.: ; Fax: S-1

2 Remnant PL No illumination Illumination, 175 mw/cm Illumination time (h) Figure S1. Remnant PL emissions of the CPB solutions obtained with and without illumination (power density of 175 mw/cm 2 ). S-2

3 45º Figure S2. HRTEM image of the pristine CPB-NCs (inset: FFT pattern). Scale bar, 2 nm. S-3

4 a b JCPDS Card No JCPDS Card No h 2 h 0.5 h 6 h 2 h 0.5 h c JCPDS Card No h 2 h 0.5 h Figure S3. (a) XRD patterns of the CPB film as a function of the illumination time (175 mw/cm 2, RH 60% in the temperature and humidity chamber), and the corresponding details in the selected 2θ regions of (b) 10º-20ºand (c) 25º-35º. S-4

5 Figure S4. XRD pattern of the CPB film fabricated by the spin coating method (all the other films mentioned in the manuscript and Supporting Information are obtained by the vacuum freeze-drying method). S-5

6 a b JCPDS Card No JCPDS Card No h 2 h 0.5 h 6 h 2 h 0.5 h c JCPDS Card No h 2 h 0.5 h Figure S5. (a) XRD patterns of the CPB film as a function of the illumination time (175 mw/cm 2, RH 80% in the temperature and humidity chamber), and the corresponding details in the selected 2θ regions of (b) 10º-20ºand (c) 25º-35º. S-6

7 a JCPDS Card No b JCPDS Card No c JCPDS Card No PbO Figure S6. (a) XRD patterns of the CPB film as a function of the illumination time (350 mw/cm 2, RH 60% in the temperature and humidity chamber), and the corresponding details in the selected 2θ regions of (b) 10º-20ºand (c) 25º-35º. It can be observed that there is a weak split peak for the (100) diffraction peak in the pristine CPB film (Figure S3b, S5b and S6b) fabricated by the vacuum freeze-drying method, but it is not present in the CPB film prepared by the spin coating method (Figure S4). There are two possible reasons for this difference. First, the thickness of the CPB film prepared with spin coating exceeds that obtained from vacuum freeze-drying, and thus some features are hid in Figure S4. Second, S-7

8 CPB-NCs are very unstable, and the generated negative pressure in the vacuum drying process may have influence on the structure of CPB-NCs. There are listed four types of JCPDS Card numbers, which are similar to the structure of CsPbBr 3 (Figure S3-S6). Unfortunately, it is still hard to identify the exact phase for the weak split peak in the (100) diffraction peak. With the higher power illumination of 350 mw/cm 2 for (Figure S6b), there is another weak split peak present in the (100) diffraction peak, which is most likely attributed to the JCPDS Card No of CsPbBr 3. Meanwhile, split peaks is also appeared in the (200) diffraction peak (Figure S3c, S5c and S6c) as the illumination time increased, and they are still consistent with the of CsPbBr 3, despite there are blue or red shifts in the peak positions. Notably, the split peaks become more obvious when the CPB film treated with the more harsh conditions (higher power density or humidity). These changes in the XRD patterns indicate the structure transformation for the CPB film, which is complicated and needed further research. S-8

9 Absorbance (a.u.) 6 h Wavelength (nm) Figure S7. UV-vis absorption spectra of the CPB film as a function of the illumination time (175 mw/cm 2, RH 60% in the temperature and humidity chamber). S-9

10 Excitation Wavelength (nm) Excitation Wavelength (nm) a b Emission Wavelength (nm) Emission Wavelength (nm) Excitation Wavelength (nm) Excitation Wavelength (nm) c d Emission Wavelength (nm) Emission Wavelength (nm) Figure S8. EEM spectra of the CPB film as a function of the illumination time (175 mw/cm2, RH 60% in the temperature and humidity chamber): (a), (b), (c) and (d). S-10

11 Table S1. Remnant PL emissions of the CPB films exposed to different conditions. Samples Power density Temperature Remnant PL (%) RH (%) Atmosphere (mw/cm 2 ) ( C) 6 h CPB-CN film Air CPB-CN film Air CPB-CN film Air CPB-CN film Air CPB-CN film Air CPB-CN film 0 (Dark) Air CPB-CN film 0 (Dark) Air CPB-CN film 0 (Dark) Air CPB-CN film 0 (Dark) Air CPB-CN film 0 (Dark) Air Sandwiched CPB-CN film Air CPB-CN film N CPB-CN film 175 high 30 N CPB-CN film Oxygen CPB-CN film 175 high 30 Oxygen S-11

12 a b c d e f Figure S9. SEM images of the CPB films on the quartz coverslips as a function of the illumination time (175 mw/cm 2, RH 60% in the temperature and humidity chamber): (a), (b) 1 h, (c), (d) 6 h and (e,f). Prior to the SEM observation, all the CPB films were coated by the thin gold layer to improve the electrical conductivity. It is difficult to observe the CPB-NCs in the initial CPB film (Figure S9a) because of their very small size and the present large amount of residual organic materials (OA, ODE or OLA). These organic materials are hard to remove after one purification step with acetone, and large PL quenching of CPB-NCs occurs if further increase the washing time. As the S-12

13 illumination time increased from 1 to 6 h, the morphologies of the CPB crystals still cannot be observed clearly (Figure S9b-d). Further illumination to, many clusters consisted of large cubic CPB crystals can be observed (Figure S9e,f). S-13

14 a b TEM observation Solution Vacuum freeze-drying Illumination c d e f g h Figure S10. Morphologies of the CPB films on the carbon coated copper grids obtained through vacuuming process. (a) Schematics of the fabrication of the CPB film on the copper grid and its illumination system. TEM images of the CPB films with different illumination times (175 mw/cm 2, RH 60% in ambient air): (b), (c), (d) 6 h and (e). (f) TEM image of the CPB film after of illumination (350 mw/cm 2, RH 60% in ambient air). TEM images of the CPB films with different illumination times (175 mw/cm 2, RH 60% in the temperature and humidity chamber): (g) and (h). Scale bar, 100 nm. Indeed, the actual arrangement of the CPB crystals on the film is not represented in the TEM images from Figure 3, because the orientational arrangement of the CPB crystals is disrupted when they scraped from the films (Figure 2a and 3a). To simulate the more real change of the S-14

15 arrangement of the CPB crystals on the film, the carbon coated copper grids are directly sank to the bottom side of the CPB solution (Figure S10a), and the thin CPB films adhered on the copper grids are obtained by the vacuum freeze-drying method. The top-viewed TEM images of the films exposed to ambient air (RH 60%) with the illumination of 175 mw/cm 2 are shown in Figure S10b-e. In comparison to the average size (7.8 nm) of the pristine CPB-NCs (Figure 1d), there is no significant increase for the resulted size of the CPB-NCs with 1 and of illumination (Figure S10b,c). But the closely-packed CPB-NC film is destroyed after, since some CPB-NC clusters with blurred crystal interface are formed. For the longer illumination of 6 h, large cubic crystals with the average size of 23.5 nm are obtained (Figure S10d). Further illumination for, parts of the sharp corners of the cubic crystals have been melted to generate the oval-shaped crystals (Figure S10e), which are more apparently present with the higher power illumination of 350 mw/cm 2 (Figure S10f). Surprisingly, the long rod-like CPB crystals can be observed in the top-viewed TEM images of the films treated in the temperature and humidity chamber (Figure S10g,h). The difference displayed with the same RH level (60%) compared to the ambient air here may be caused by the air supply system in the temperature and humidity chamber, which promotes the air flow rate in the chamber, and the carbon coated copper grid is more greatly affected by the internal condition. Furthermore, the above changed morphologies are different from those scraped from the quartz coverslip (Figure 3), which may be caused by the effects from the thin carbon layer or the copper grid, but they can represent the actual arrangements of the CPB crystals in some degree. On the other hand, these formed CPB crystals with a wide size distribution by controlling the illumination, S-15

16 RH and the air flow rate may provide a new way to generate different shaped CPB crystals, instead of the synthesis approaches. 1-3 S-16

17 Norm. PL (a. u.) 1 Pristine CPB film 3.09 ns, ns, aver ns 175 mw/cm 2, RH 60% 3.48 ns, ns, aver ns 350 mw/cm 2, RH 60% 4.01 ns, ns, aver ns Time (ns) Figure S11. Time-resolved PL decays and the fitted curves for the CPB films on the quartz coverslip: Pristine CPB film is detected at 516 nm with excitation of 460 nm, and the CPB films after of illumination (175 and 350 mw/cm 2, RH 60% in the temperature and humidity chamber) are detected at 524 nm with excitation of 460 nm. S-17

18 Intensity (a. u.) Intensity (a. u.) Intensity (a. u.) Intensity (a. u.) a c C-O Carbonate C=O Binding Energy (ev) Binding Energy (ev) Cs 3d 3/2 C-N C-C C=C Cs 3d 5/2 C 1s Cs 3d b Binding Energy (ev) d Si-O (Substrate) C=O Br 3d 3/2 C-O Br 3d 5/2 Carbonate Pb-O O 1s Br 3d Binding Energy (ev) Binding Energy (ev) Figure S12. High-resolution XPS spectra of (a) C 1s, (b) O 1s, (c) Cs 3d and (d) Br 3d as a function of the illumination time (175 mw/cm 2, RH 60% in the temperature and humidity chamber). The PbCO 3 and PbO phases may be formed from the reaction among CsPbBr 3, H 2 O, O 2 and CO 2. 4 First, the hydrated CsPbBr 3 species, such as CsPbBr 3 H 2 O might be generated because of the hydrophilic property of CsPbBr Then, the dehydration reaction might be expressed as: 4 2CsPbBr 3 H 2 O + 1 O2 + CO 2 2CsBr + PbCO 3 + Pb(OH) 2 + 2HBr + Br 2 (1) 2 Pb(OH) 2 might be decomposed to PbO and H 2 O: Pb(OH) 2 PbO + H 2 O (2) S-18

19 Table S2. Chemical element contents of the CPB films obtained from XPS analysis. Samples Atomic ratios CPB film Pb: Cs: Br: O: C = 1: 0.59: 2.22: 0.98: CPB film Pb: Cs: Br: O: C = 1: 0.59: 2.37: 3.81: CPB film Pb: Cs: Br: O: C = 1: 0.24: 1.18: 8.27: CPB film Pb: Cs: Br: O: C = 1: 0.28: 1.17: 16.36: S-19

20 a 8 days No illumination in water b 8 days Illumination in water Figure S13. (a) Optical images of two kinds of the sandwiched CPB films with one exposed a half of its film to water (no illumination). (b) Optical images of the CPB film (one part sandwiched in the quartz coverslips and another part directly exposed to water) in water as a function of the illumination time (175 mw/cm 2 ). S-20

21 a b c d Figure S14. (a) TEM and (b) HRTEM images of the CPB crystals scraped from the film exposed to oxygen after of illumination (175 mw/cm 2 ). (c) TEM and (d) HRTEM images of the CPB crystals scraped from the film exposed to oxygen with high water vapor after of illumination (175 mw/cm 2 ). S-21

22 a JCPDS Card No b JCPDS Card No c d JCPDS Card No JCPDS Card No Figure S15. (a) XRD patterns of the CPB film exposed to oxygen as a function of the illumination time (175 mw/cm 2 ), and (b) the corresponding detail in the selected 2θ region of 25º-35º. (c) XRD patterns of the CPB film exposed to oxygen with high water vapor as a function of the illumination time (175 mw/cm 2 ), and (d) the corresponding detail in the selected 2θ region of 25º-35º. S-22

23 a b Figure S16. (a,b) SEM images of the CPB film after of illumination with high RH of 80% in the temperature and humidity chamber (175 mw/cm 2 ). References (1) Akkerman, Q. A.; Motti, S. G.; Srimath Kandada, A. R.; Mosconi, E.; D'Innocenzo, V.; Bertoni, G.; Marras, S.; Kamino, B. A.; Miranda, L.; De Angelis, F.; Petrozza, A.; Prato, M.; Manna, L. Solution Synthesis Approach to Colloidal Cesium Lead Halide Perovskite Nanoplatelets with Monolayer-Level Thickness Control. J. Am. Chem. Soc. 2016, 138, (2) Sun, S.; Yuan, D.; Xu, Y.; Wang, A.; Deng, Z. Ligand-Mediated Synthesis of Shape-Controlled Cesium Lead Halide Perovskite Nanocrystals via Reprecipitation Process at Room Temperature. ACS Nano 2016, 10, (3) Shamsi, J.; Dang, Z.; Bianchini, P.; Canale, C.; Stasio, F. D.; Brescia, R.; Prato, M.; Manna, L. Colloidal Synthesis of Quantum Confined Single Crystal CsPbBr 3 Nanosheets with Lateral Size Control up to the Micrometer Range. J. Am. Chem. Soc. 2016, 138, S-23

24 (4) Huang, W.; Huang, W.; Manser, J. S.; Kamat, P. V.; Ptasinska, S. Evolution of Chemical Composition, Morphology, and Photovoltaic Efficiency of CH 3 NH 3 PbI 3 Perovskite under Ambient Conditions. Chem. Mater. 2016, 28, (5) Sharma, S.; Weiden, N.; Weiss, A. Phase Transitions in CsSnCl 3 and CsPbBr 3. An NMR and NQR Study. Z. Naturforsch. A 1991, 46, (6) Leguy, A. M. A.; Hu, Y.; Campoy-Quiles, M.; Alonso, M. I.; Weber, O. J.; Azarhoosh, P.; van Schilfgaarde, M.; Weller, M. T.; Bein, T.; Nelson, J.; Docampo, P.; Barnes, P. R. F. Reversible Hydration of CH 3 NH 3 PbI 3 in Films, Single Crystals, and Solar Cells. Chem. Mater. 2015, 27, S-24