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1 DOI: 1.138/NMAT365 Solution coating of large-area organic semiconductor thin films with aligned single-crystalline domains Ying Diao 1, Benjamin C-K. Tee, Gaurav Giri 1, Jie Xu 1,5, Do Hwan Kim 1, Hector A. Becerril 1, Randall M. Stoltenberg 3, Tae Hoon Lee, Gi Xue 5, Stefan C. B. Mannsfeld 4 * & Zhenan Bao 1 * 1 Department of Chemical Engineering, Stanford University, Stanford, California 9435, USA. Department of Electrical Engineering, Stanford University, Stanford, California 9435, USA. 3 Department of Chemistry, Stanford University, Stanford, California 9435, USA. 4 Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 945, USA. 5 Department of Polymer Science and Engineering, Institute of Chemistry and Chemical Engineering, The State key Laboratory of Coordination Chemistry, The National Laboratory of Nanjing Microstructure Study, Nanjing University, Nanjing, 193, P. R. China. Corresponding authors: Zhenan Bao, zbao@stanford.edu; Stefan CB Mannsfeld, mannsfel@slac.stanford.edu NATURE MATERIALS 1

2 Supplementary methods and discussion DOI: 1.138/NMAT365 COMSOL simulations. The detailed geometry of the simulation box is as follows. The outer diameter and inner diameter of the crescent-shaped micropillar is 35 μm and 3 μm respectively. The pillar height is 4 μm (measured from the SEM image). The center-to-center spacing between the micropillars is 5 μm. The corners of the micropillars are rounded with a radius of curvature (fillet radius in COMSOL) of 3 μm. The tilt of the blade is set as 8. The gap of the first row of pillars to the bottom substrate is set as 3 μm. To simulate shearing motion, the bottom substrate was set as a sliding wall with speed of -.6mm/s. The negative sign denotes the direction pointing towards the left of the simulations box (opposite to the x axis). The two side walls were set as periodic boundary conditions. The outlet (from the left bound of the simulation box, Figure S1) was set as atmospheric pressure. The inlet mass flow rate was set as the solvent evaporation rate. From the mass of solid films we calculated the solvent evaporation rate by applying the mass balance. 1 Normal mass flow rate at the inlet is calculated as x 1-9 kg/s at the shearing conditions specified in the methods section. Simulation is performed at the steady state using the laminar fluid module. X-ray characterization of film microstructure and molecular packing. Azimuthal X-ray scans, high-resolution scans and grazing incidence X-ray diffraction were performed at the Stanford Synchrotron Radiation Lightsource (SSRL) on beamlines 7-, -1 and At beamline 11-3, we performed grazing incidence X-ray diffraction (GIXD) with an area detector (MAR345 image plate) for obtaining molecular packing information. The extent of deviation from the equilibrium molecular packing was inferred from the positions of (11) and (1) diffraction peaks. The beam energy is 1.73 kev. The incident angle was set as.1. Two scans were performed for each sample under helium protection, one with the shearing direction parallel to the incident beam, the other perpendicular. We carried out high-resolution azimuthal X-ray scans at beamline 7-, equipped with a point detector of 1mrad collimation. The beam energy is 8 kev. The incident angle was set as.1. The detector was positioned at the (1) reflection, with the momentum transfer vector q xy =.81, q z =.1. The highresolution scans for obtaining the correlation length were performed at beamline -1. The beam energy was set as 1.3 kev. The crystal analyzer was employed to reduce instrumental broardening by the soller slits. The point detector was positioned on the (1) diffraction peak (q z =.38). The step size of the high-resolution scan was.6. Two types of scans were performed: specular scan (thelta-thelta scan) for obtaining out-of-plane peak width and transverse scan (rocking scan, or thelta scan) for obtaining in-plane peak width. Scherrer equation was applied for calculating the correlation length from the full width at half maximum (FWHM) of the peak. Polymorphs of TIPS-pentacene via diffraction peak analysis. Grazing Incidence X-ray Diffraction (GIXD) scans were performed at beamline 1-5 of Stanford Synchrotron Radiation Lightsource (SSRL). For films with highly aligned grains such as the ones used in this study, sample in-plane rotation is necessary to capture all diffraction peaks and detect every polymorph present in the film. To improve the data quality for detailed peak analysis, small sample areas (<3x3 mm ) were used to reduce sampleinduced peak broadening and to eliminate edge effects. At least three samples were scanned for each solution shearing condition. The new data we obtained reveal at least two discrete packing states (polymorphs) in TIPS-pentacene thin films (Figure S9, Figure 4). The discerning of discrete polymorphs is made possible by the higher crystal quality and thus narrower diffraction peak widths compared to those from the previous study. When comparing the column sum of (1L) and (1L) peaks at various conditions (Figure S9), we noticed that many of the diffraction spectra are comprised of two peaks, a sharp peak at Q xy (1L) ~.88 Å -1, Q xy (1L) ~.77 Å -1 and a broad peak with Q xy (1L) between.81 and.86 Å -1 and Q xy (1L) between.78 and.83 Å -1. Interestingly, with increase in shearing speed or decrease in solution concentration, the broad peak shifts towards the sharp peak while the sharp peak positions remain invariant. This observation suggests that the broad peak is comprised of multiple peaks, which when their relative intensities vary gives rise to an apparent shift in the position of the NATURE MATERIALS

3 DOI: 1.138/NMAT365 SUPPLEMENTARY INFORMATION convoluted peak. We therefore carried out peak deconvolution on the most intense diffraction peaks to find that a minimum of four peaks can be used to fit all the diffraction spectra, representative ones shown in Figure S1. The existence of at least four polymorphs can also be inferred from the fine structures of GIXD images, as exhibited in the (-11L) rod in Figure S11. However, we cannot exclude the existence of alternative solutions to the peak deconvolution, especially if more than four polymorphs are present. Tradeoff between molecular packing control and morphology control. Higher shearing speed also resulted in increased crystal growth defects, which severely limited the chance of obtaining singlecrystalline domains. Specifically, at the conditions when the desired molecular packing was obtained in the previous work, 3 the film morphology was dictated by undesired spherulite formation due to random nucleation across the entire film (Figure S13A). This phenomenon is usually observed when a complete liquid film forms before nucleation occurs, i.e., the Landau-Levich regime of solution coating. 1 Under this regime, controlling fluid dynamics at the meniscus front will have no effect on nucleation and crystal growth, making it impossible to obtain single-crystalline domains using FLUENCE. This limitation calls for alternative means for controlling molecular packing, which can achieve nonequilibrium molecular packing at lower shearing speeds when nucleation and crystal growth ensue at the meniscus front, concurrent with the liquid film formation, a.k.a the evaporation regime of solution coating. In this work, we are able to attain non-equilibrium molecular packing in the evaporation regime by changing the solvent and tuning the film thickness, in addition to varying the shearing speed. NATURE MATERIALS 3

4 DOI: 1.138/NMAT365 Supplementary figures Figure S1. Streamline representation of the calculated velocity field. The streamlines are color coded to indicate the scale of velocity, in mm/s. To simulate the effect of shearing towards the right, the substrate has a sliding speed of.6 mm/s towards the left, while the shearing blade is fixed. Recirculation and lateral currents are highlighted using white dotted lines in B-D. 4 NATURE MATERIALS

5 DOI: 1.138/NMAT365 SUPPLEMENTARY INFORMATION Figure S. Morphology comparison of TIPS-pentacene films prepared with flat shearing blade (A) and micropillar patterned blade (B), at various shearing speed. Images are taken under crosspolarized optical microscope. All images are of the same scale. Films coated with micropillar-patterned blade at shearing speed from.4 to 1. mm/s exhibit significantly increased domain size, and much lower grain boundary density and void fraction. Figure S3. Design of nucleation control region and the resulting morphology of TIPS pentacene films. Images were taken under cross-polarized optical microscope. A-B, effect of tip angle on nucleation density and the resulting film morphology. Smaller tip angle leads to lower nucleation density, and better nucleation anchoring at the tip. C, Twin boundary formation with symmetric triangle design. D, Effect of the number of slits on crystallite filtering. The tip angle is 3. The slit width is NATURE MATERIALS 5

6 DOI: 1.138/NMAT365 1 μm. The stripe widths in A, B, D are 5 μm. Films were solution sheared from 8mg/ml TIPSpentacene/toluene solution, at 5 C and.5 mm/s (A, B, D) or at 35 C and. mm/s (C). These solution-shearing conditions were selected because the crystal growth is free of secondary nucleation, and as such, the nucleation control method can be investigated independent of the crystal growth control method. All other data presented in this work were based on TIPS-pentacene/mesitlyene system as specified in the methods section. 5µm nm Figure S4. AFM height image of single-crystalline domains corresponding to Figure C. The white arrow indicates the solution shearing direction. The depth profile is shown along the white dotted line. The depth of the hollows corresponds to the thickness of the film, which is ± 1 nm. Crystal terraces of ~1.7nm height are also visible from this image, demonstrating high crystal quality and singlecrystalline nature of the domain. 6 NATURE MATERIALS

7 DOI: 1.138/NMAT365 SUPPLEMENTARY INFORMATION Figure S5. Cross-polarized optical micrographs showing cases of non-single-crystalline domains. The films were solution sheared with FLUENCE at optimized conditions specified in the Methods section. The crossed arrows indicate the orientation of crossed polarizers. Rotating cross-polarizers by ~35 distinguishes single-crystalline from non-single-crystalline domains in sample 1 (A and B) and sample (C and D). This figure shows that there are two types of morphology defects preventing us from attaining higher probability of single-crystalline domains. The nonidealities are either surface defect induced or twin grain boundary induced shown in Figure S6. These morphology defects occur stochastically under the same solution coating conditions. Figure S6. Cross-polarized optical micrographs showing causes for non-single-crystalline domains: Surface defects induced (A, B) and twin grain boundary induced (C, D). C and D are images of the same sample with mirror rotations to show twin domains. The sampe has Au electrode on some of the single-crystalline domains. All films were solution sheared with FLUENCE at optimized conditions specified in the Methods section. Figure S7. TIPS-pentacene film morphology with high probability of aligned single-crystalline domains. Nucleation control region design: tip angle is 15 ; strip width is 5 μm (indicated by white NATURE MATERIALS 7

8 DOI: 1.138/NMAT365 arrows); slit size is 5 μm. Solution shearing conditions are detailed in the Methods section. The following steps were taken for attaining > 9% probability of aligned single-crystalline domains: 1) narrowing the domain size from 1 mm to 5 μm; ) reducing surface defects by excessive substrate cleaning; 3) tuning the slit design to reduce meniscus instabilities, and that include adopting a tapering design around the slit region, as shown in Figure S7 A. This helps avoid sudden stop of fluid at the slit region. Figure S8. μm wide single-crystalline domains of TIPS-pentacene. A and B show the crystal morphology under different tilting angles of the cross-polarizers. Simultanous light extinction of all domains indicates highly aligned nature of the single-crystalline domains. The films were solution sheared at the same conditions detailed in the method section (135 C from 1.6mg/ml mesitylene solution at.6mm/s). FLUENCE was applied for obtaining the single-crystaline domains. This image, together with Figure S7 and Figure demonstrate that FLUENCE can be applied to making a wide size range of single-crystalline domains (, 5, 1μm shown). 8 NATURE MATERIALS

9 DOI: 1.138/NMAT365 SUPPLEMENTARY INFORMATION NATURE MATERIALS 13 Macmillan Publishers Limited. All rights reserved

10 DOI: 1.138/NMAT365 Shearing speed (mm/s) A1 (1) (1) (-11) (11) (-1) (1L) (1L) A A3 III IV II I A4 I II III IV B1 B B B C1 C C C D1.6 D D D Q z (Å -1 ) Q xy (Å -1 ) Q xy (Å -1 ) Figure S1. Characterization of molecular packing by Grazing Incidence X-ray diffraction (GIXD) and corresponding diffraction peak analysis. A1-D1, GIXD images of TIPS-pentacene films prepared from 8mg/ml solution at various shearing speeds. GIXD was taken with sample in-plane rotation to capture diffraction peaks from all crystal planes of all polymorphs present. The observed brag rods (red arrows on top) are labeled with their (hk) indexes. Indexes of degenerate peaks are not shown. The amorphous ring from SiO (gate dielectric) is visible at q from Å -1, whose intensity increases with decrease in film thickness. A-D, higher magnification images of (1L) and (1L) peaks, corresponding to the region highlighted with the white dotted box in A1. The diffracton intensities are shown on log scale. A3-D3 & A4-D4, analysis of polymorphic states via deconvolution of (1L) and (1L) peaks, with A3-D3 corresponds to (1L) and A4-D4 to (1L). Blue curve is simulated from deconvoluted peaks, and the red curve is experimentally measured, made by performing a column summation of the D diffraction image shown in Figure A-D. The simulated blue curve overlays very well with the corresponding red curve in all cases. Peak deconvolution suggests existence of at least four polymorphs of TIPS-pentacene. The four polymorphs are labeled form I, II, III, IV respectively. 1 NATURE MATERIALS

11 DOI: 1.138/NMAT365 A.8 (1) (1) (-11) B.7 SUPPLEMENTARY INFORMATION IV III II I Q xy (Å -1 ) Q xy (Å -1 ) Figure S11. GIXD image indicating existence of four TIPS-pentacene polymorphs. A, GIXD image of the TIPS-pentacene film coated from 3.mg/ml mesitylene solution at.8mm/s. The (hk) indexes of the (1), (1) and (-11) brag rods are shown on top. Indexes of the degenerate peaks are not shown. B, higher magnification image of the (-11) peak, corresponding to the region highlighted with the black dotted lines in A. Background substraction is applied to increase the signal-to-noise ratio. The color map used is bone for enhancing the contrast. Thickness (nm) mg/ml 8.mg/ml Thickness (nm) mm/s ~17 nm Shearing speed (mm/s) Concentration (mg/ml) Figure S1. Thickness of TIPS-pentacene films coated at various conditions. The grey dotted line indicates the film thickness below which the highest deviation from the equilibrium packing is obtained. Films with thickness above the gray dotted line exhibited mixed polymorphs. NATURE MATERIALS 11

12 DOI: 1.138/NMAT365 Figure S13. Morphology comparison of TIPS-pentacene films coated from toluene solution (A) to that from mesitylene solution (B) at respective lowest solution shearing speed when the highest deviation from equilibrium packing is obtained. Solution shearing was carried out at 8mg/ml, 9 C, 8mm/s from toluene solution, and 8mg/ml, 135 C,.8mm/s from mesitylene solution. Table S1. Hole mobility of TIPS-pentacene measured perpendicular (per) and parallel (par) to the shearing direction. Average mobility (cm V -1 s -1 ) Single-crystalline Reference per par 8.1. par/per ~5 ~ Samples were prepared at.6 mm/s shearing speed from mesiytlene solution (see Methods section). par/per denotes the ratio of mobility parallel over perpendicular to the shearing direction. Charge transport anisotropy is much higher for single-crystalline domain than reference samples, which corroborates the highly aligned feature of single-crystalline domains. For reference samples, the crystal ribbons intersect due to dendritical crystal growth. In addition, the domain orientation distribution is also much broader. These factors may have resulted in higher mobility in the perpendicular direction for the reference sample. 1 NATURE MATERIALS

13 DOI: 1.138/NMAT365 SUPPLEMENTARY INFORMATION 1 1 Control Referene Single-crystalline Max. value Mobility, cm^/vs Shearing speed, mm/s Figure S14. Mobility comparison at various shearing speeds. Samples were solution sheared from 1.6 mg/ml TIPS-pentacene-mesitylene solution at 135 C. Around 3 transistors tested in each case. Invariance of reference sample mobilities at various shearing speeds indicates the charge transport is grain boundary limited. For single-crystalline domain samples, maximum mobility at intermediate shearing speed may be due to interplay between morphology and molecular packing. The molecular packing was characterized with GIXD shown in Figure S9 C, D. I sd (x1-3 A) V g =-1V -9V -8V -7V -6V -. -5V -4V. -3V V sd (V) -8-1 Figure S15. Representative transfer characteristics of the TIPS-pentacene single-crystalline devices, supplementary to device characteristics shown in Figure 5. NATURE MATERIALS 13

14 DOI: 1.138/NMAT365 Figure S16. Optical micrograph of TIPS-pentacene single-crystalline thin-film transistors. Devices were fabricated in the top-contact, bottom-gate configuration, with 4 nm thick Au drain and source electrodes (shown as dark horizontal lines on the middle single-crystalline domain) and PTS-modified SiO dielectric layers (3 nm). The channel length and width were 5 μm and 1 mm, respectively. The crossed arrows denote the orientation of the crossed polarizers. Figure S17. Film morphology of 4T-TMS (trimethylsilyl-substituted quarterthiophene), singlecrystalline domains (with FLUENCE) vs. reference samples (without FLUENCE). A, a photographic image of one millimeter-wide single-crystalline OFET pixels on a Si wafer with 3 nm SiO as the dielectric. B, molecular structure of 4T-TMS. C-F, optical micrographs of single-crystalline domains (C, D) and reference samples (E, F) without (C, E) and with (D, F) cross-polarizers. G & H, higher manification optical images of single-crystalline domains vs reference films. All samples were prepared via solution shearing at 14 C from mg/ml tetralin solution, at.mm/s. 14 NATURE MATERIALS

15 DOI: 1.138/NMAT365 SUPPLEMENTARY INFORMATION Figure S18. Comparison of film morphology characterized by AFM: single-crystalline (with FLUENCE) vs. reference (without FLUENCE). Depth profiles are shown beneath corresponding AFM images, measured along the white dotted line. Crystal terraces of ~nm height are visible on single-crystalline film surface, demonstrating high crystal quality and single-crystalline nature of the domain. The terrace height corresponds to the height of one 4T-TMS monolayer. In the reference sample, dendrites are evident, and the depth of hollows corresponds to the thickness of the film, which is approximately 1 nm. 1 Le Berre, M., Chen, Y. & Baigl, D. From Convective Assembly to Landau-Levich Deposition of Multilayered Phospholipid Films of Controlled Thickness. Langmuir 5, , doi:1.11/la83646e (9). Rivnay, J. et al. Large modulation of carrier transport by grain-boundary molecular packing and microstructure in organic thin films. Nature Materials 8, , doi:1.138/nmat57 (9). 3 Giri, G. et al. Tuning charge transport in solution-sheared organic semiconductors using lattice strain. Nature 48, 54-U14, doi:1.138/nature1683 (11). NATURE MATERIALS 15