Color-Pure Violet Light-Emitting Diodes Based on Layered Lead ...
Supporting Information for
Color-Pure Violet Light-Emitting Diodes Based on Layered Lead Halide Perovskite Nanoplates Dong Liang1†, Yuelin Peng2†, Yongping Fu1, Melinda J. Shearer1, Jingjing Zhang1, Jianyuan Zhai1, Yi Zhang1, Robert J. Hamers1, Trisha L. Andrew1*, Song Jin1* 1
Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
2
Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
†These authors contributed equally to this work *To whom the correspondence should be addressed: [email protected] and [email protected]
S1
1. Ultraviolet photoemission spectroscopy (UPS) results on (PEA)2PbBr4 Figure S1 shows the UPS spectra of layered perovskite (PEA)2PbBr4 thin film and nanoplates on gold substrates. The valence band maximum (VBM) was determined by linear extrapolation of valence band onset subtracted to the background around Fermi level. The background as a result, VBM positions of (PEA)2PbBr4 thin film and nanoplate sample are at 0.99 eV and 1.27 eV below the Fermi level EF.
Figure S1. (A) UPS spectra for (PEA)2PbBr4 polycrystalline thin film (blue) and nanoplates (red) obtained by DMF vapor annealing. (B) Zoom-in UPS spectra. (C) Zoom-in UPS spectra show the position of Fermi Levels to vacuum level for both samples. (D) Zoom-in UPS spectra show the positions of VBM relative to Fermi level E F, set to 0, for both samples. 2. Effect of precursor solution concentration on the nanoplate morphology Changing the concentration of (PEA)2PbBr4 perovskite precursor solution in DMF will change not only the thickness of the (PEA)2PbBr4 nanoplates after DMF vapor annealing, but also the morphology and coverage of the nanoplates on the substrates. The nanoplates were thinner and the coverage on the substrate was lower, if the precursor solution
S2
concentration was lower, as shown in Figure S2 and summarized in Table 1 in the main text. When the precursor solution concentration was reduced from 6.7 wt% to 3.4 %wt, the (PEA)2PbBr4 product morphology after DMF vapor annealing changed from nanoplates to needle-like nanoribbons and the coverage decreased significantly.
Figure S2. Representative optical images showing the effect of the concentration of the precursor solutions in DMF on the morphology of nanoplates after DMF vapor annealing. The nanoplates are on the ITO/PEDOT:PSS substrates. The precursor solution concentration changed from 3.4 %wt to 13.4 %wt. The scale bar is 10 μm. 3. Effect of precursor solution concentration on the LED performance. As we introduced in the manuscript, the thickness of the nanoplates changes from 30 to 100 nm as the precursor solution concentration increases from 3.4 wt% to 13.4 wt%. The LED devices based on nanoplates with different thickness showed varying device performances. As shown in Figure S3, the highest EQE was achieved when the precursor concentration used was 6.7 wt%.
Figure S3. The dependence of LED EQE on the concentration of the precursor solution used. S3
4. Effect of TPBi thickness on the LED performance. We have adjusted the thickness of TPBi in the perovskite nanoplate LEDs. The final structure introduced in the manuscript text with 35 nm thick TPBi layer reached the best device EQE value due to its balanced charge carriers in the emitting layer. When we increased the TPBi thickness from 35 nm to 40 nm, an obvious luminescence peak from TPBi can be observed in the electroluminescence curve as Figure S4A shows. This is because that unbalanced electron and hole recombined at the layer of TPBi instead of perovskite nanoplates. Therefore, the LED performance decreases. The peak EQE value is only 0.028% as shown in Figure S4B, which is much lower than the value of LED device with 35 nm TPBi layer. A
B
Figure S4. (A) Normalized luminescence of a LED device based on (PEA)2PbBr4 nanoplates
with 40 nm TPBi. (B) Current-voltage J-V dependence (red symbols) and EQEs (blue symbols) for LEDs with 40 nm TPBi fabricated with (PEA)2PbBr4 thin film (open symbols) and nanoplates (solid symbols).
S4
Color-Pure Violet Light-Emitting Diodes Based on Layered Lead Halide Perovskite Nanoplates Dong Liang1†, Yuelin Peng2†, Yongping Fu1, Melinda J. Shearer1, Jingjing Zhang1, Jianyuan Zhai1, Yi Zhang1, Robert J. Hamers1, Trisha L. Andrew1*, Song Jin1* 1
Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
2
Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
†These authors contributed equally to this work *To whom the correspondence should be addressed: [email protected] and [email protected]
S1
1. Ultraviolet photoemission spectroscopy (UPS) results on (PEA)2PbBr4 Figure S1 shows the UPS spectra of layered perovskite (PEA)2PbBr4 thin film and nanoplates on gold substrates. The valence band maximum (VBM) was determined by linear extrapolation of valence band onset subtracted to the background around Fermi level. The background as a result, VBM positions of (PEA)2PbBr4 thin film and nanoplate sample are at 0.99 eV and 1.27 eV below the Fermi level EF.
Figure S1. (A) UPS spectra for (PEA)2PbBr4 polycrystalline thin film (blue) and nanoplates (red) obtained by DMF vapor annealing. (B) Zoom-in UPS spectra. (C) Zoom-in UPS spectra show the position of Fermi Levels to vacuum level for both samples. (D) Zoom-in UPS spectra show the positions of VBM relative to Fermi level E F, set to 0, for both samples. 2. Effect of precursor solution concentration on the nanoplate morphology Changing the concentration of (PEA)2PbBr4 perovskite precursor solution in DMF will change not only the thickness of the (PEA)2PbBr4 nanoplates after DMF vapor annealing, but also the morphology and coverage of the nanoplates on the substrates. The nanoplates were thinner and the coverage on the substrate was lower, if the precursor solution
S2
concentration was lower, as shown in Figure S2 and summarized in Table 1 in the main text. When the precursor solution concentration was reduced from 6.7 wt% to 3.4 %wt, the (PEA)2PbBr4 product morphology after DMF vapor annealing changed from nanoplates to needle-like nanoribbons and the coverage decreased significantly.
Figure S2. Representative optical images showing the effect of the concentration of the precursor solutions in DMF on the morphology of nanoplates after DMF vapor annealing. The nanoplates are on the ITO/PEDOT:PSS substrates. The precursor solution concentration changed from 3.4 %wt to 13.4 %wt. The scale bar is 10 μm. 3. Effect of precursor solution concentration on the LED performance. As we introduced in the manuscript, the thickness of the nanoplates changes from 30 to 100 nm as the precursor solution concentration increases from 3.4 wt% to 13.4 wt%. The LED devices based on nanoplates with different thickness showed varying device performances. As shown in Figure S3, the highest EQE was achieved when the precursor concentration used was 6.7 wt%.
Figure S3. The dependence of LED EQE on the concentration of the precursor solution used. S3
4. Effect of TPBi thickness on the LED performance. We have adjusted the thickness of TPBi in the perovskite nanoplate LEDs. The final structure introduced in the manuscript text with 35 nm thick TPBi layer reached the best device EQE value due to its balanced charge carriers in the emitting layer. When we increased the TPBi thickness from 35 nm to 40 nm, an obvious luminescence peak from TPBi can be observed in the electroluminescence curve as Figure S4A shows. This is because that unbalanced electron and hole recombined at the layer of TPBi instead of perovskite nanoplates. Therefore, the LED performance decreases. The peak EQE value is only 0.028% as shown in Figure S4B, which is much lower than the value of LED device with 35 nm TPBi layer. A
B
Figure S4. (A) Normalized luminescence of a LED device based on (PEA)2PbBr4 nanoplates
with 40 nm TPBi. (B) Current-voltage J-V dependence (red symbols) and EQEs (blue symbols) for LEDs with 40 nm TPBi fabricated with (PEA)2PbBr4 thin film (open symbols) and nanoplates (solid symbols).
S4
