Efficient Light-Emitting Diodes based on Nano- Crystalline Perovskite ...
Efficient Light-Emitting Diodes based on NanoCrystalline Perovskite in a Dielectric Polymer Matrix Guangru Li, Zhi-Kuang Tan, Dawei Di, May Ling Lai, Lang Jiang, Jonathan Hua-Wei Lim, Richard H. Friend and Neil C. Greenham* Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, UK
*[email protected]
Supporting Information
Experimental Details: Materials: F8 polymer was provided by Cambridge Display Technology (CDT) and was used as received. Polyimide precursor (product number PI2525) was ordered from HD microsystems and was diluted into a concentration of 20 mg/ml in N-methyl-2-pyrrolidone before use. All other chemicals, if not specified, were ordered from Sigma-Aldrich and were used as received. CH3NH3PbBr3 perovskite synthesis: Methylammonium bromide (CH3NH3Br) was prepared by adding 33 wt% methylamine solution in ethanol (24mL) and 48 wt% hydrobromic acid in water (8.5 mL) to 100 mL of absolute ethanol. The reaction mixture was stirred at room temperature in a nitrogen atmosphere. The solvent was removed by rotary evaporation until white crystals started to appear. The crystals were collected by Büchner funnel filtration and were dried overnight under vacuum at 80 °C. The perovskite precursor solution was prepared by mixing
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CH3NH3Br and PbBr2 at a 3:2 molar ratio in anhydrous N,N-dimethylformamide (DMF, from ROMIL) to give a concentration of 5 wt%. PeLED fabrication: Blend solutions were prepared by mixing 5 wt% CH3NH3PbBr3 solutions and diluted PIP solutions to give different weight ratios. The blend solutions were stirred at room temperature for 2 hours before use. The mixed solutions ranged from colorless to light-orange colored depending on the blending ratio. ITO-coated glass substrates were cleaned with acetone and isopropanol for 15 minutes separately, followed by 10 minutes oxygen plasma treatment. PEDOT:PSS (Clevios P VP Al 4083) was spin coated on ITO substrates at 6000 rpm for 30 seconds and annealed at 140 °C for 30 minutes in a nitrogen glovebox. The blend solutions were spin-coated onto PEDOT:PSS at 3000 rpm for 30 seconds and annealed at 60 °C for 1 minute. A solution of F8 in chlorobenzene (10 mg mL-1) was spin coated on top of the PIP: perovskite layer at 3000 rpm for 30 seconds to give a 50 nm film. We note that PIP is insoluble in chlorobenzene and is unaffected by the deposition of the F8 layer. Ca (20 nm) and Ag (100 nm) were successively deposited by vacuum thermal evaporation at vacuum better than 3×10-6 mbar. Devices were tested in air immediately after taking out of glovebox without additional encapsulation. PeLED characterization: Current vs. voltage characteristics were measured using a Keithley 2400 Source Measure Unit. Photon flux was measured simultaneously using a calibrated silicon photodiode centred over the light-emitting pixel. Luminance in cd/m2 was calculated based on the emission spectrum of the PeLED, and on the known spectral response of the silicon photodiode. External quantum efficiency was calculated assuming a Lambertian emission profile. Electroluminescence spectra were measured using a Labsphere CDS-610 spectrometer.
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SEM characterization: SEM images were taken by using the in-lens detector in a LEO 1550 system. The acceleration voltage was set at 10 kV. The chamber pressure was below 1×10-5 mbar.
Figure S1. XRD data of films spin-coated on quartz substrate with different PIP/perovskite weight ratios. The estimated crystal size for PIP/perovskite 1/2 w/w is 70 nm. The crystal sizes of perovskite-only and PIP/perovskite 1/10 w/w films cannot be determined because of instrumental broadening. X-ray diffraction patterns were measured under ambient conditions. The samples were scanned using a Bruker D8 Advance diffractometer with copper radiation source and a position-sensitive (LynxEye) detector.
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Figure S2. AFM images: (a) scratched edge of PEDOT-PSS film on ITO substrate (washed by DMF solvent), and its cross-section profile; (b) scratched PIP: perovskite/PEDOT-PSS film of mixing ratio 1/10 w/w, and its cross-section profile; (c) scratched PIP: perovskite/PEDOT-PSS film of mixing ratio 1/2 w/w, and its cross-section profile. The estimated average thickness of PEDOT: PSS film is 18±2 nm, the estimated thickness of PIP is 7±2 nm in PIP/perovskite 1/10 w/w film and 30±3 nm in PIP/perovskite 1/2 w/w film. AFM images were taken in tapping mode using a DimensionTM 3100 system.
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Figure S3. Comparison of current density vs. voltage characteristics of PIP: perovskite 1:2 by weight and PIP-only devices.
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*[email protected]
Supporting Information
Experimental Details: Materials: F8 polymer was provided by Cambridge Display Technology (CDT) and was used as received. Polyimide precursor (product number PI2525) was ordered from HD microsystems and was diluted into a concentration of 20 mg/ml in N-methyl-2-pyrrolidone before use. All other chemicals, if not specified, were ordered from Sigma-Aldrich and were used as received. CH3NH3PbBr3 perovskite synthesis: Methylammonium bromide (CH3NH3Br) was prepared by adding 33 wt% methylamine solution in ethanol (24mL) and 48 wt% hydrobromic acid in water (8.5 mL) to 100 mL of absolute ethanol. The reaction mixture was stirred at room temperature in a nitrogen atmosphere. The solvent was removed by rotary evaporation until white crystals started to appear. The crystals were collected by Büchner funnel filtration and were dried overnight under vacuum at 80 °C. The perovskite precursor solution was prepared by mixing
1
CH3NH3Br and PbBr2 at a 3:2 molar ratio in anhydrous N,N-dimethylformamide (DMF, from ROMIL) to give a concentration of 5 wt%. PeLED fabrication: Blend solutions were prepared by mixing 5 wt% CH3NH3PbBr3 solutions and diluted PIP solutions to give different weight ratios. The blend solutions were stirred at room temperature for 2 hours before use. The mixed solutions ranged from colorless to light-orange colored depending on the blending ratio. ITO-coated glass substrates were cleaned with acetone and isopropanol for 15 minutes separately, followed by 10 minutes oxygen plasma treatment. PEDOT:PSS (Clevios P VP Al 4083) was spin coated on ITO substrates at 6000 rpm for 30 seconds and annealed at 140 °C for 30 minutes in a nitrogen glovebox. The blend solutions were spin-coated onto PEDOT:PSS at 3000 rpm for 30 seconds and annealed at 60 °C for 1 minute. A solution of F8 in chlorobenzene (10 mg mL-1) was spin coated on top of the PIP: perovskite layer at 3000 rpm for 30 seconds to give a 50 nm film. We note that PIP is insoluble in chlorobenzene and is unaffected by the deposition of the F8 layer. Ca (20 nm) and Ag (100 nm) were successively deposited by vacuum thermal evaporation at vacuum better than 3×10-6 mbar. Devices were tested in air immediately after taking out of glovebox without additional encapsulation. PeLED characterization: Current vs. voltage characteristics were measured using a Keithley 2400 Source Measure Unit. Photon flux was measured simultaneously using a calibrated silicon photodiode centred over the light-emitting pixel. Luminance in cd/m2 was calculated based on the emission spectrum of the PeLED, and on the known spectral response of the silicon photodiode. External quantum efficiency was calculated assuming a Lambertian emission profile. Electroluminescence spectra were measured using a Labsphere CDS-610 spectrometer.
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SEM characterization: SEM images were taken by using the in-lens detector in a LEO 1550 system. The acceleration voltage was set at 10 kV. The chamber pressure was below 1×10-5 mbar.
Figure S1. XRD data of films spin-coated on quartz substrate with different PIP/perovskite weight ratios. The estimated crystal size for PIP/perovskite 1/2 w/w is 70 nm. The crystal sizes of perovskite-only and PIP/perovskite 1/10 w/w films cannot be determined because of instrumental broadening. X-ray diffraction patterns were measured under ambient conditions. The samples were scanned using a Bruker D8 Advance diffractometer with copper radiation source and a position-sensitive (LynxEye) detector.
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Figure S2. AFM images: (a) scratched edge of PEDOT-PSS film on ITO substrate (washed by DMF solvent), and its cross-section profile; (b) scratched PIP: perovskite/PEDOT-PSS film of mixing ratio 1/10 w/w, and its cross-section profile; (c) scratched PIP: perovskite/PEDOT-PSS film of mixing ratio 1/2 w/w, and its cross-section profile. The estimated average thickness of PEDOT: PSS film is 18±2 nm, the estimated thickness of PIP is 7±2 nm in PIP/perovskite 1/10 w/w film and 30±3 nm in PIP/perovskite 1/2 w/w film. AFM images were taken in tapping mode using a DimensionTM 3100 system.
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Figure S3. Comparison of current density vs. voltage characteristics of PIP: perovskite 1:2 by weight and PIP-only devices.
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