Pentacene derivative/DTTCNQ cocrystals: alkyl-confined mixed heterojunctions with molecular alignment and transport property tuning

Soluble pentacene-based complexes were successfully prepared and short contact interactions induced alignment driving forces to eliminate C/S disorders. Cocrystal packing and charge transport properties were tailored by adjusting the solvent.

and toluene (C 7 H 8 , HPLC) were purchased from Sigma-Aldrich. All the materials were used directly without further purification.

Single Crystal Growth and Structural Analysis
For the growth of single crystal, the mixture of TMTES-P (1.2 mg) and DTTCNQ (0.6 mg) with molar ratio of 1:1 were dissolved in chlorobenzene (1 ml) and toluene (1 ml), respectively, and placed in reagent bottles. Then the prepared solutions were heated up to 110°C or 120°C lasted ∼2 h to ensure complete dissolution. After that the as-prepared solution was put into a petri dish with approximately tilted 20°∼30°. As the solvent slowly evaporates, dark black needle-like cocrystals can be observed at the bottom of the petri dish for approximately 3∼4 days. Then cleaned with alcohol and dried in air. The single crystal structures of cocrystal P1 and P2 were obtained using a Bruker Smart-1000-CCD diffractometer, and using graphite-monochromated Mo Kα radiation (λ = 0.71073 Å). Exposure times of 10 s for all cocrystals were applied. The X-ray crystallographic data were collected at 277 K for cocrystal P1, 300 K for cocrystal P2. The structure was resolved by the direct method and refined by the full-matrix least-squares method on

Growth of the Self-Assembled Micro/nanocrystals and Device Fabrication
The organic field-effect transistors (OFETs) were constructed by using the temperature to obtain P1 and P2 micro/nanoribbons. Gold was thermally evaporated onto cocrystals as the source and drain electrodes (50 nm thickness), using copper grid as the shadow mask. All measurements were performed at room temperature in air condition. The morphology of micro/nanocrystals were observed by using an optical microscope (BX53, Olympus).

Measurements
The UV-vis-NIR absorption spectra were recorded by a LAMBDA 35 spectrometer. Infrared (IR) spectra of the cocrystals were recorded with a PE-Spectrum Two spectrometer, the single crystals S-5 were mixed with KBr, completely grounded and then pressed into the slice for IR measurements.
Powder X-ray diffraction (PXRD) was performed on a D/max2500 with Cu Kα source (κ = 1.5418 Å), the data were collected in the 2θ range 5-30° at room temperature. Elemental analyses were (1) Where I D is the source-drain current, C i is the capacitance per unit area of the dielectric layer, V T is the threshold voltage, W and L are the channel width and length, μ is the charge carrier mobility, V GS is the gate-source voltage, respectively.

Theoretical calculation
The calculation of transfer integral is based on neutral molecular orbitals. 1 Under several assumptions, the transfer integral is approximated by the coupling strength between two orbitals (HOMO and HOMO-1, or LUMO and LUMO-1), which can be expressed by Equation (2): Where, V ij is the coupling of orbital i and j, their corresponding wavefunctions are and . H is the Hamiltonian. Due to the electronic polarization of molecule, the effective transfer integral is corrected by Prof. Bredas, 2 which is the method we used here. The electronic couplings were calculated under the level of DFT/PW91PW91/6-31G (d), which was implemented in Gaussian 09.
ig. S1 Preparation of the TMTES-P/DTTCNQ single crystal with a 20°30° orientation as the optimized condition for the solvent evaporation.

Fig. S2
The intermolecular distance of the cocrystal P1.