A Transparent Perovskite Light Emitting Touch-

Transcription

1 Supporting Information for A Transparent Perovskite Light Emitting Touch- Responsive Device Shu-Yu Chou, Rujun Ma, Yunfei Li,, Fangchao Zhao, Kwing Tong, Zhibin Yu, and Qibing Pei*, Department of Materials Science and Engineering, Henry Samueli School of Engineering and Applied Science, University of California Los Angeles, Los Angeles, CA 90095, USA qpei@seas.ucla.edu Department of Electronics Science and Engineering, State Key Laboratory on Integrated Optoelectronics, Jilin University, Changchun , China Department of Industrial and Manufacturing Engineering, High-Performance Materials Institute, FAMU-FSU College of Engineering, Florida State University, Tallahassee, FL 32310, USA S1

2 Semi-Transparent Light-Emitting Touch Responsive Device (Figure S1) Figure S1. Transparent property of perovskite LETD. Transmittance spectra of a perovskite LETD with a 10 ohm/ AgNW-PU composite electrode as the top electrode. The LETD has the structure of glass/ito/pedot:pss (40nm)/ MAPbBr3:PEO (200nm)/AgNW-PU. The transmittance of the LETD at 550 nm is ~68% as shown in Figure S1. S2

3 Stress (MPa) Mechanical Property of the AgNW-PU Electrode (Figure S2) Tensile Strain (%) (%) Figure S2. Stress-Strain curve of AgNW-PU at room temperature. The tensile stress-strain curve was measured with a dynamic mechanical analyzer (DMA) at a stretching rate of 1 mm s -1 at room temperature. In Figure S2, the AgNW-PU electrode shows a maximum tensile strain of 110%. The Young s modulus was calculated to be 31 MPa. S3

4 MAPbBr3:PEO Morphology and Grain Size (Figure S3) Figure S3. SEM images of perovskite/polymer composite thin films with MAPbBr3:PEO ratio of (a) 1:0, (b) 1:0.2, (c) 1:0.3, (d) 1:0.4, (e) 1:0.5, (f) 1:0.7. When no PEO additive was present, the resulting perovskite film had a surface coverage of less than 60% and the crystal grains were larger than 1um (Figure S3a). When PEO was added, the crystal size dramatically reduced, and the surface coverage of the film increased. At the optimized MAPbBr3:PEO ratio of 1:0.3, the perovskite grain achieved its minimum size (~20 nm) and the surface coverage of the film reached its maximum (>90%), as shown in Figure S3c. As the concentration of PEO continued to increase, PEO began to precipitate out and larger grain sizes were observed. S4

5 LETD Pressure Sensitivity Study. (Figure S4) Current (ma) Current (ma) Pressure Applied (Pa) (Pa) Figure S4. Transient current response at low to high pressure range. Different loads were applied onto the pero LETD and the results showed a constant current output, which indicated that as long as a stable contact was made, the brightness and current were fixed regardless of the pressure loading. This was due to constant resistance at the AgNW surface regardless of the applied pressure. S5

6 PL Spectrum versus EL Spectrum (Figure S5). Normalized Intensity (a.u.) (a.u.) PL EL Wavelength (nm) (nm) Figure S5. Comparison between (black) PL spectrum of MAPbBr3:PEO film and (red) EL spectrum of pero LETD. S6

7 Durability of AgNW:Pero Interface. (Figure S6) Frequency: 1.67 Hz 0.4 Current (ma) Number of Touch Counts Counts Figure S6. Durability test of pero LETD at frequency of 1.67 Hz. The output is presented with current variation. A durability test of AgNW:Pero interface was performed and the results can be found in Figure S6. Here, an instantaneous contact was formed and deformed repeatedly over 1100 cycles under a 1.67 Hz frequency. The supplied bias was 4 V, and after over 1100 cycles, there was no change in current output. This further proves there was no change in the sheet resistance of the AgNW- PU electrode after the continuous motion. S7

8 Stability Test under Ambient Conditions. (Figure 7) Figure S7. Luminance performance with air exposure time for pero LETD. The LETD was fabricated under ambient conditions, and the device luminance remained stable up to approximately 200 hours after storing under ambient lab air. S8

9 Fabrication of Ag/PEO:Pero/Ag Device. (Figure S8) Figure S8. Illustration of Ag/MAPbBr3:PEO/Ag device. The detailed architecture of the Ag/MAPbBr3:PEO/Ag device is illustrated in Figure S8. The PEO:Pero solution was first spin-coated onto a cleaned glass substrate, then it was thermal annealed at 60 C for 3 minutes. Next, Ag was thermally evaporated at a pressure < 10-6 mbar with thickness of 100 nm with shadow mask. The distance between the two Ag electrodes is 50 μm. S9

10 AgNW-PU Deformation. (Figure S9) (a) (b) a A 0 A f h a Figure S9. Deformation of AgNW-PU transparent electrode created by a tweezer s tip pointing down onto the LETD device. A deformation shape of a square-base pyramid is observed here. Stress Diagram is shown in the Inset Figure. Figure S9 shows that when pressure was exerted onto a small region of the AgNW-PU transparent electrode, the electrode deformed into a trapezoid shape when a stable contact was made with the pero film below. From Figure S9, the point contact area was relatively small compared to the AgNW-PU film; the deformation created by this point contact was treated as a square-based pyramid shape for ease of calculation. This allows the calculation of the total area expansion of the AgNW-PU electrode when pressure was applied. The area expansion and the measured elastic modulus of the electrode then allowed the calculation for the required pressure to create a stable Schottky contact. S10

11 Total area expansion of the AgNW-PU transparent electrode. The area strain of AgNW-PU substrate can be calculated by the following Equation (1): Area Strain (%) = % of area change = Af A 0 A 0 100% (1) where A0 is the original area of the AgNW-PU film before deformation, and Af is the total area of the film after deformation. The AgNW-PU film was in a square shape with its edge (a) being 15mm. A0 is the area of the square film and was calculated to be 225 mm 2. Assuming the air gap height (h) is 0.1 mm, Af can be computed by finding the total surface area of the 4 triangles of the square-based pyramid, and it was calculated to be mm 2. The area strain was then calculated as 0.89%. In this calculation, we assumed that the thickness of the electrode stayed constant during the deformation. Biaxial Elastic Modulus. In order to calculate biaxial stress, the biaxial elastic modulus must be determined. Since the film thickness was small compared to the total LETD thickness, and the lateral dimensions of the AgNW-PU were much greater than the film thickness, the biaxial elastic modulus (M) can be correlated to the Young s modulus (E) by 1 M = E 1 υ (2) where υ is the poisson ratio. Young s modulus of the electrode was measured to be 31 MPa by DMA, and the poisson ratio for elastomer was ~0.5. Thus, the biaxial elastic modulus was calculated to be 62 MPa. The elastic modulus was calculated from the tensile stress-strain curve in Figure S2. From the stress-strain curve, it can be observed that within 8% strain, stress increased linearly with strain. All the calculated strains were within 8%; thus, the calculated E can be used in the calculation here. S11

12 Pressure Required (MPa) Pressure Required (MPa) Calculation of Biaxial Stress. By knowing the biaxial strain and biaxial elastic modulus, biaxial stress can be calculated according to Equation (3). σ = M ε (3) where σ is the biaxial stress; this is also the minimum pressure required to create a Schottky contact for the pero LETD. The minimum required pressure was calculated to be 551 Pa. In Figure S10, the minimum required pressure for various air gap heights was also calculated and shown in the plot Air Gap Height (um) Air Gap Height (um) Figure S10. Calculated pressure required to make a stable contact based on different air gap heights. S12

13 Rigid Pixelated Perovskite LETD. (Figure S11) Figure S11. A rigid LETD with an array of pixels (10 x 10). The pixels that sense the applied pressure emit green light. The emissive area of each pixel size is 0.8 mm x 0.8 mm, while the spacer grid has 0.2 mm grid line width and 40 μm grid thickness. S13

14 Operation of a flexible LETD under bending. (Figure S12) Figure S12: Photograph of an LETD under bending to 6 mm. Light emission is observed when the device is pressed with a tweezer tip. REFERENCES (1) Nix, W. D. Mechanical Properties of Thin Films. Metall. Trans. A 1989, 20, S14