OLED from solution-processed crystalline poly(triazine imide)

Synthesis of PTI-LiBr : 1 g of precursor dicyandiamide (DCDA, Sigma Aldrich >99%) is ground with a vacuum dried eutectic salt mixture of LiBr and KBr (Sigma Aldrich /Acros Organics >99%) (15 g; 52:48 wt%, m.p. 348°C) in a glovebox. The reaction mixture is filled into a quartz ampule and sealed. The sealed quartz ampule is placed vertically into a furnace (Nabertherm, L 5/11/B180, 2.4 kW) at 400 °C for 4 h. Then the temperature is increased (10 K/min) to the final condensation temperature for the desired timeframe. The ampule is removed at room temperature, opened, and the salt block is dissolved in dest. Water in a 50 mL Falcon. The slurry is centrifuged and the supernatant is decanted. The pellet is re-dispersed in hot water on a shaker and centrifuged again. The supernatant is decanted and the process is repeated for two times with hot water and two times with methanol (>99% for synthesis). The resulting pellet is redispersed in methanol and the methanol is evaporated. The resulting powder is dried under vacuum at 200 °C for 24 h. The furnace geometry and temperature homogeneity play a role for the synthesis of organic materials at temperatures close to carbonization. For repeatable experiments the ampule should be placed at the same spot in the furnace. using PTI-LiBr Film thickness measurements: For extraction of conductivity film thickness values have been obtained with an Olympus LEXT laser scanning microscope. Fourier transform infrared (FT-IR) : Spectra were recorded from solid on a Thermo Scientific Nicolet iS5 spectrometer (Thermo Fisher Scientific, Waltham, MA, USA) in the wavenumber range of 4000-600 cm-1 with resolution of 4 cm-1. Raman : UV Raman spectra were recorded with a Horiba T64000 spectrometer in single-grating mode. The excitation source was provided by a diode-pumped solid-state laser from CryLas at a wavelength of 266 nm and power of 4 mW. The light was focused on the sample with a Thorlabs LMU-40x-UVB objective (backscattering geometry). A notch filter with cut-off at 220 cm -1 was used to filter out the elastically scattered light. The acquired Raman spectra were calibrated by comparison with the spectrum of a Ga 2 O 3 crystal by using a quadratic calibration curve. This procedure allows for reduction of the experimental error at approximately 5 cm -1 , which is below the spectral resolution of 8 cm -1 . Powder X-ray : Structural analysis of the prepared PTI-MX was performed with a Bruker D2 Phaser X-Ray powder diffractometer (XRD) in Bragg-Brentano geometry. X ‐ rays were generated by a Cu K α1+2 source at 30 kV operating voltage and collected with a LynxEye detector. Photoluminescence, Photoluminescence excitation, quantum yield, Lifetime : Edinburgh Instruments FLS 980 spectrometer. Photoluminescence, photoluminescence excitation and quantum yield were measured using a Xe lamp. The quantum yield was determined in a direct excitation set up with an integrating sphere. Films were drop-casted from ethanol dispersions on quartz substrates PGO 10x10x0.5 mm. Further, it is important to note that the presented samples were prepared and characterised on


PTI-IF
First-principle calculations: First-principles calculations are performed on model monolayer structures featuring various protonation conditionssee Figure S7. The unit cell of the PTI monolayer is formed by 18 atoms which comprise the two triazine rings and three imide bridges atoms and the system is assumed to be periodic only in the planar directions. 10 Å of vacuum are included in the directions perpendicular to the layer to avoid unphysical interactions between the replica. Protonation is realized by placing one dissociated HCl molecule per unit cell in proximity to the protonation site (nitrogen at one triazine ring or nitrogen at one imide-bridge, see Figure S7a ) and then relaxing the system. The explicit inclusion of the Cl counterion ensures charge neutrality and includes the electrostatic effect of the anion on the protonated system. The equilibrium position of the Cl − ion, relative to the protonated backbone, is obtained with a further structural optimization of the whole system that places it at the pore centre as shown in Figure S7b-c.
Ground state calculations are performed from spin-restricted DFT [Hohenberg P and Kohn W Phys. Rev. 136 B864 (1964) and Kohn W and Sham L J Phys. Rev. 140 A1133 (1965] as implemented in the pseudopotential, plane-wave code Quantum Espresso (QE). A uniform 6x6x1 k-mesh is adopted to sample the Brillouin zone, the PBE functional [REF Perdew J P, Burke K and Ernzerhof M Phys. Rev. Lett. 77 3865 (1996)] is used to approximate the exchange-correlation potential, optimized norm conserving pseudopotentials are employed with 50 Ry (200 Ry) plane-wave cut-off to represent the wavefunctions (charge density). The pairwise Tkatchenko-Scheffler scheme [A. Tkatchenko and M. Scheffler, Phys. Rev. Lett. 102, 073005 (2009)] is adopted to include dispersion interactions. The structures are optimized without imposing any symmetry constraint until residual interatomic forces are smaller than 10 −5 Ry/Bohr. Optical absorption spectra reported are computed from time-dependent DFT [Runge andGross Physical Review Letters. 52 (12): 997-1000 (1984)] in the linear-response approach. For these calculations the turbo-TDDFT routine of QE is used, implementing the Liouville−Lanczos algorithm. A Lorentzian of 130 meV is applied to each peak.

Preparation of PTI-LiBr dispersions:
Sonication of Flakes was conducted with a BANDELIN HD 2200/-U (200 W, HF 20 kHz) sonotrode setup with a MS72 sonotrode with the amplitude set to 10% in continuous mode. 30 mg of PTI-LiBr and 5 mL dist. water are added into a 50 mL falcon tube. The falcon tube is placed in an ice bath and the sonotrode has been immersed about 3-5 mm into the dispersion. Dispersions are sonicated for 3 h, centrifuged at 7690 g for 1 min to reduce large particles and the supernatant was removed from the pellet with a pipet into a falcon. Dispersions with different HCl concentration for optical experiments were prepared by adding 50 μL of the PTI-LiBr dispersion to 3 mL of a corresponding HCl dilution.
Photoconductor characterisation: Thorlabs LED 375 nm has been controlled by a Keithley 2461 in pulse mode at 3.6 V and a current limit of 1 A. The pulse chain was set to 1 s bias and 5 s off repeating ten times. The interdigitated substrate was contacted by an ossila board "Push-Fit Test Board for Photovoltaic Substrates (8 pixel)" and IV characterisation was conducted with a source measure unit (4200A SCS parameter analyser; Keithley). The current without 375 nm irradiation was determined to be 0.050 μA, with irradiation the current was 0.122 μA at a film thickness of 100 μm and 20 V applied. Fourier transform infrared (FT-IR): Spectra were recorded from solid on a Thermo Scientific Nicolet iS5 spectrometer (Thermo Fisher Scientific, Waltham, MA, USA) in the wavenumber range of 4000-600 cm-1 with resolution of 4 cm-1.
Raman: UV Raman spectra were recorded with a Horiba T64000 spectrometer in single-grating mode. The excitation source was provided by a diode-pumped solid-state laser from CryLas at a wavelength of 266 nm and power of 4 mW. The light was focused on the sample with a Thorlabs LMU-40x-UVB objective (backscattering geometry). A notch filter with cut-off at 220 cm -1 was used to filter out the elastically scattered light. The acquired Raman spectra were calibrated by comparison with the spectrum of a Ga2O3 crystal by using a quadratic calibration curve. This procedure allows for reduction of the experimental error at approximately 5 cm -1 , which is below the spectral resolution of 8 cm -1 .
Powder X-ray: Structural analysis of the prepared PTI-MX was performed with a Bruker D2 Phaser X-Ray powder diffractometer (XRD) in Bragg-Brentano geometry. X-rays were generated by a Cu Kα1+2 source at 30 kV operating voltage and collected with a LynxEye detector.
Photoluminescence, Photoluminescence excitation, quantum yield, Lifetime: Edinburgh Instruments FLS 980 spectrometer. Photoluminescence, photoluminescence excitation and quantum yield were measured using a Xe lamp. The quantum yield was determined in a direct excitation set up with an integrating sphere. Films were drop-casted from ethanol dispersions on quartz substrates PGO 10x10x0.5 mm. Further, it is important to note that the presented samples were prepared and characterised on the same day. Diffusion of protons in PTI-LiBr has not been studied yet. It is possible that crystals of PTI-LiBr are not fully protonated because the system has had not enough time to equilibrate. This might explain why the luminescence of the basic Li-defect is still present in acidic solutions. Lifetime measurements were conducted with an Edinburgh Instruments 375 nm pulsed laser set to a 50 ns pulse period. Evaluation was conducted with the instrument software choosing a two exponential decay function.

UV-Vis:
UV-VIS-measurements were performed in ambient conditions with a PerkinElmer Lambda 950 spectrometer in standard transmission operation, 1 nm step size. Films were measured on 10x10x0.5 mm quartz substrates. Dispersions were measured in a quartz cuvette with 1 cm optical path.
XPS: JOEL JPS-9030 Photoelectron Spectrometer with an Al kα (1486 eV) excitation source and a monochromator. Quantitative comparison of nitrogen and carbon in single spectra were performed by signal integration after background subtraction of a Shirley function. The samples were prepared by drop-casting PTI dispersions (MeOH) on ITO coated glass substrates to minimize charging and to avoid background carbon signals from e.g. carbon tape as substrate.
ssNMR: Cross polarization magic-angle spinning (CP-MAS) solid-state NMR spectra were recorded on a Bruker Avance 400 MHz spectrometer operating at 100.6 MHz ( 13 C).
SEM: SEM images have been recorded with a GeminiSEM 500 electron microscope (Carl Zeiss GmbH, Germany).
OLED preparation: ITO-coated glass substrates (sheet resistance = 20 Ω per square) were cleaned by sequential sonication (10 minutes) in (i) acetone and (ii) isopropanol followed by drying via a nitrogen gun. The substrates were then treated via O2 plasma (partial pressure 1.2 × 10 −1 mbar) for 15 minutes at 10.2 W. 50 nm PEDOT:PSS (Osilla) films were spin coated as hole injection layer and heated to 220 °C for 10 min. PTI-LiBr was drop casted from solution. 5 nm Calcium and 200 nm Aluminium were evaporated in a PVD chamber at 10 -5 mbar. Finally the OLEDs were encapsulated with UV-curable resin (Osilla) and a glass slide. Current density-       . PTI single monolayer relaxed structures in-vacuo, relative to PTI-IF (a), the triazine-protonated (b) and the imide-bridge protonated (c) backbones. In the protonated structures we have also reported the formation energies per unit-cell volume evaluated as the difference between the total energy of the protonated system and the sum of the energies of the separated pristine monolayer and HCl subsystems. Figure S9. a) Comparison of photoconductor employing PTI-LiBr from 600 °C and 550 °C. Charge transport and photocurrent are absent in the 600 °C material due to the observed partial carbonization (black line). In the device employing PTI-LiBr from 550 °C current is able to cross the channel of the interdigitated substrate and photocurrent is observed when excited with a 375 nm LED focused on the device with a lens. b) Irradiance dependent IV sweep of photoconductor device. Increased irradiance with a 375 nm LED results in increased current flow. The low current is result of the polycrystalline material property (grain boundaries) and likely energetic disorder at partially intercalation free layers. b) IV sweeps of an interdigitated device employing 550 °C, 48 h product with different sweep speed. The observed hysteresis is due to migration of Li + and Brions.