Switchable Charge Injection Barrier in an Organic Supramolecular Semiconductor

Transcription

1 SUPPORTING INFORMATION to Switchable Charge Injection Barrier in an Organic Supramolecular Semiconductor Andrey. V. Gorbunov 1, Andreas.T Haedler 2, Tristan Putzeys 3, R. Helen Zha 2, Hans-Werner Schmidt 4, Milan Kivala 5, Indre Urbanavičiūtė 6, Michael Wübbenhorst 3, E. W. Meijer 2, Martijn Kemerink 1,6,* 1 Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands 2 Institute of Complex Molecular Systems, Laboratory of Macromolecular and Organic Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands 3 Department of Physics and Astronomy, Laboratory for Soft Matter and Biophysics, KU Leuven, Celestijnenlaan 200D, B-3001 Heverlee, Belgium 4 Makromolekuläre Chemie I, Bayreuther Institut für Makromolekülforschung (BIMF), and Bayreuther Zentrum für Kolloide und Grenzflächen (BZKG), Universität Bayreuth, Bayreuth, Germany 5 Lehrstuhl für Organische Chemie I, Department Chemie und Pharmazie, Friedrich-Alexander- Universität Erlangen-Nürnberg, Erlangen, Germany 6 Complex Materials and Devices, Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, Sweden *corresponding author martijn.kemerink@liu.se S-1

2 Contents SUPPORTING INFORMATION Synthesis of a-cbt DSC and FT-IR of a-cbt AFM images of drop cast films Charging curves from DWM Dielectric relaxation spectroscopy Symmetric Au/α-CBT/Au devices... 8 References to SI S-2

3 1 Synthesis of a-cbt 3,4,5-tri(octyloxy)benzoic acid chloride as peripheral building block and 2,6,10-triamino carbonylbridged triarylamine as core building block were synthesized following literature procedures. 1 3 Scheme S1: Synthesis of a-cbt from 3,4,5-tri(octyloxy)benzoic acid chloride and 2,6,10-triamino carbonyl-bridged triarylamine. Carbonyl-bridged triarylamine trisamide a-cbt: Full name: 2,6,10-Tris-(3,4,5-trioctyloxybenzoylamino)-4H,8H,12H-benzo[1,9]quinolizino-[3,4,5,6,7- defg]-acridine-4,8,12-trione Under dry conditions, 0.2 ml Pyridine (2.27 mmol, 5 eq.) and 167 mg 2,6,10-triamino carbonylbridged triarylamin (0.45 mmol, 1 eq.) were added at 0 C to a solution of 1.2 mg 3,4,5-tri((S)-3,7- dimethyloctyloxy)benzoic acid chloride (2.27 mmol, 5 eq.) in 16 ml NMP. The reaction mixture was heated to 70 C and stirred for 6 days. Then the solution was poured into ice water and the precipitate was filtered off. The crude product was recrystallized from DMF with a small amount of THF, filtered and washed with diethyl ether. The product was obtained as bright orange powder in 55 % yield (460 mg). 1 H-NMR (300.1 MHz, o-dcb-d 4 /DMSO-d 6 ): δ = 1.06 (m, 27H aliph. ), 1.44 (m, 72H aliph. ), 1.73 (m, 18H aliph. ), 2.06 (m, 18H aliph. ), 4.30 (m, 18H, OCH 2 CH 2 ), (s, 6H, (CO)CCHC), 9.81 (s, 6H, CCHC), (s, 3H, (CO)NH) ppm; 13 C-NMR (75.5 MHz, o-dcb-d 4 /DMSO-d 6 ): δ = 13.7, 22.3, 26.0, 29.1, 30.3, 31.5, 68.5, 72.6, 106.1, 122.7, 128.1, 131.9, 132.6, 137.2, 140.8, 152.3, 164.7, ppm; IR (neat): ṽ = 3321 (m), 3089 (w), 2954 (s), 2923 (s), 2854 (s), 1662 (s), 1651 (s), 1601 (m), 1582 (m), 1532 (s), 1497 (s), 1462 (s), 1429 (s), 1380 (m), 1330 (s), 1225 (s), 1212 (s), 1109 (s), 914 (m), 888 (m), 797 (m), 757 (m) cm 1 ; MALDI-TOF-MS: m/z calcd for the Ag-adduct C 132 H 204 AgN 4 O 15 [M] g/mol, found g/mol; thermally stable up to 300 C, melting was not observed below decomposition temperature. S-3

4 2 DSC and FT-IR of a-cbt Fig. S1 Differential scanning calorimetry (DSC) traces of a-cbt with heating and cooling rates of 10 K/min. As can be seen from the DSC traces there is no sign of any phase transition up to 250 C. There are also no phase transitions at higher temperatures. The materials is thermally stable up to 300 C, melting was not observed below the decomposition temperature. Fig. S2 Temperature dependent FT-IR spectra, showing the N-H stretching vibration region upon cooling with 10 K/min from 215 C to 30 C. Spectra are shown for every 15 C. S-4

5 3 AFM images of drop cast films Fig. S3 Typical AFM topography (a total vertical scale 38 nm, b vertical scale 158 nm) and phase (c vertical scale 38, d vertical scale 30 ) images of annealed (without electric field) drop casted films of a-cbt. Panels (a, c) show film which was annealed at 100 C for 30 min immediately after deposition on bottom gold contact, whereas panels (b, d) correspond to films that were annealed a second time at a higher temperature T = C for 2 h. AFM scans were taken in tapping mode. Small surface features are best visible as a contrast on phase images, local cross-sections (e, f) taken at the blue circles on panels (c, d) represent these features in degrees of phase. The typical height of the observed surface steps is 5-10 nm whereas average width 20 nm. The terrace-like topography is indicative of an in-plane orientation of (bundles of) the π-stacked columns for both the as-cast and annealed films. S-5

6 4 Charging curves from DWM Fig. S4. Driving voltage and measured current in the double wave method (DWM) for Al/a-CBT/Al capacitor device at f = 50 mhz. Data correspond to the measurement in Fig. 4(a) in the main text. Subtraction of the response to the second wave from the first wave, followed by integration gives the polarization P vs. applied field E curve in Fig. 4(a). The imperfect closure of the PE-curve indicates the presence of hysteretic background signals caused by e.g. mobile ions or switchable injection currents. Fig. S5. Driving voltage and measured current in the double wave method (DWM) for Au/a-CBT/Au diode device at f 100 mhz. S-6

7 5 Dielectric relaxation spectroscopy Fig. S6. 3D DRS spectrum for a-cbt at variable temperatures and frequencies. (Left) The loss spectrum as measured and (right) a conductivity-corrected loss spectrum; peaks correspond to relaxation processes. Above 100 C, a relaxation at 20 Hz is visible, which could indicate molecular rotation. Fig. S7. 2D dielectric spectrum for a-cbt vs. temperature for different frequencies. Starting from 100 C, the low frequency dielectric constant increases, until 200 C, where it reaches a maximum. The stepwise increase at 80 C can be attributed to a higher degree of mobility in the alkyl side chains, 4 while at 200 C the order in columnar stacks decreases, reducing the permittivity. S-7

8 6 Symmetric Au/α-CBT/Au devices Fig. S8. je characteristic and on/off ratio of a nominally symmetric Au/a-CBT/Au device, showing resistive switching at both polarities. Thin dotted lines indicate the coercive field E C 13 V/µm, arrows indicate the sweep direction. The observed asymmetry between positive and negative poling is attributed to differences related to the order of deposition (active layer by solution processing on Au vs. Au by thermal evaporation on the active layer). Fig. S9. je characteristics showing the on-current of a symmetric Au/a-CBT/Au diode probed immediately after complete switching: the positive (negative) branch is measured after a positive (negative) field pulse exceeding the coercive field. The on-state is stable and no further switching is observed upon sweeping up and down as indicated by the arrows. S-8

9 Fig. S10. je curves of a not-aligned Au/aCBT/Au device at temperatures below the temperature at which interfacial dipoles can be aligned and switching can be observed. Fig. S11. je curves of a symmetric Au/a-CBT/Au diode, showing the stability of the on-current upon partial reversal of the scan direction, as indicated by the colored arrows. S-9

10 Fig. S12. je curves of a symmetric Au/a-CBT/Au diode, demonstrating the influence of the sweep frequency on resistive switching, cf. Fig. 4(b) of the main text where a similar shift of the coercive field with sweep speed is shown. Blue and red curves are measured at f 25 mhz and f 40 mhz, respectively. References to SI (1) Molla, M. R.; Das, A.; Ghosh, S. Self-Sorted Assembly in a Mixture of Donor and Acceptor Chromophores. Chem. Eur. J. 2010, 16 (33), (2) Field, J. E.; Venkataraman, D. HeterotriangulenesStructure and Properties. Chem. Mater. 2002, 14 (3), (3) Fang, Z.; Teo, T.-L.; Cai, L.; Lai, Y.-H.; Samoc, A.; Samoc, M. Bridged Triphenylamine-Based Dendrimers: Tuning Enhanced Two-Photon Absorption Performance with Locked Molecular Planarity. Org. Lett. 2009, 11 (1), 1 4. (4) Wu, Z.; Petzold, A.; Henze, T.; Thurn-Albrecht, T.; Lohwasser, R. H.; Sommer, M.; Thelakkat, M. Temperature and Molecular Weight Dependent Hierarchical Equilibrium Structures in Semiconducting Poly(3-Hexylthiophene). Macromolecules 2010, 43 (10), S-10