Research ArticleMATERIALS SCIENCE

Robust, high-performance n-type organic semiconductors

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Science Advances  01 May 2020:
Vol. 6, no. 18, eaaz0632
DOI: 10.1126/sciadv.aaz0632
  • Fig. 1 Typical aggregated structures of high-performance OSCs and the molecular design of BQQDI.

    (A and B) Typical herringbone- and brickwork-type packing structures of high-performance p-type and n-type OSCs. (C) Chemical structures and molecular designs used in this work. Displayed molecular orbital is the LUMO. Right side shows the calculated electrostatic potential map.

  • Fig. 2 Synthesis and fundamental chemical properties of BQQDI derivatives.

    (A) Scheme for the syntheses of BQQ–TCDA and BQQDI derivatives (C8–BQQDI, PhC2–BQQDI, and 4-Hep–BQQDI). (B) Cyclic voltammograms obtained from 4-Hep–PDI (0.5 mM; blue), 4-Hep–BQQDI (0.5 mM; red), and PDI–FCN2 (0.2 mM; green) in benzonitrile. (C) Time-dependent UV-vis spectra obtained from 4-Hep–BQQDI in benzonitrile (4 × 10−6 M) under ambient air. (D) TG plots obtained from PhC2–BQQDI (blue) and C8–BQQDI (red) at a heating rate of 1 K min−1 under a stream of nitrogen. Inset: DTA data up to 400°C. a.u., arbitrary units.

  • Fig. 3 Crystal structures and results of electron transport calculations for BQQDIs and PDI−FCN2.

    (A to F) Aggregate structures in single crystals and results of charge transport calculations based on structural coordination. For C8–BQQDI: (A) lateral intermolecular interactions and short contacts, (D) short contacts and estimates of transfer integrals in the direction of brickwork-type packing. For PhC2–BQQDI: (B) lateral intermolecular interactions and short contacts, (E) short contacts and estimation of transfer integrals in the direction of brickwork-type packing. For PDI–FCN2: (C) lateral intermolecular interactions and short contacts, (F) short contacts and estimates of transfer integrals in the direction of brickwork-type packing.

  • Fig. 4 Packing structures and electron transport properties calculated for C8–PDI and PhC2–PDI.

    Molecular and crystal structures of (A) C8–PDI and (B) PhC2–PDI PhC2–PDI. Transfer integrals and angle-resolved values of the inverse of effective mass for (C) C8–PDI and (D) PhC2–PDI. (E) Angle-resolved effective mass. The effective mass is shown in unit of the rest mass of an electron.

  • Fig. 5 TFT evaluations and theoretical analyses.

    (A) General TFT structure used in this work. Details of the components are described in the respective captions. (B to D) Transfer characteristics of PC-TFTs [Sub = G = n++-Si; Ins = SiO2 (200 nm) + DTS-SAM, Ci = 17.3 nF cm−2; S/D = Au (40 nm)] based on PhC2–BQQDI, PhC2–PDI, and PDI–FCN2, respectively. Red and blue symbols indicate data acquired under Ar and ambient air, respectively. Black dashed lines fit the square root of drain current (|ID|1/2), allowing μe to be estimated. (E) A polarized microscopy image of a PhC2–BQQDI SC-TFT (L = 190 μm, W = 136 μm) [Sub = G = n++-Si; Ins = SiO2 (200 nm) + AL-X601 (60 nm), Ci = 12.5 nF cm−2; S/D = Au (40 nm)]. (F) The corresponding output characteristics and (G) transfer characteristic (VD = 75 V). Black dashed and magenta solid lines represent the fit to |ID|1/2 and the slope of an electrically equivalent ideal TFT (41). (H) Gated Hall effect data obtained from a PhC2–BQQDI SC-TFT at 300 K. At VG ≥ 35 V, the transverse voltage (Vtrans, colored dots) was modulated using an applied magnetic field (B, purple solid line). (I) Packing structures in the ac- and ab-planes with estimation of the inverses of effective masses for C8–BQQDI. (J) Packing structures in the bc- and ab-planes with estimates for the inverses of effective masses for PhC2–BQQDI. (K) Packing structures in the bc- and ab-planes with estimates of the inverses of effective mass for PDI–FCN2. (L) Angle-resolved effective masses for C8–BQQDI, PhC2–BQQDI, and PDI–FCN2. Arrows indicate the channel directions of the SC-TFTs evaluated in this work. (M and N) Color-coded B-factor distributions (unit: Å2 s−1) for PhC2–BQQDI and PDI–FCN2 obtained from the trajectories during the last 20 ns of a 100-ns MD run. (O) Statistical distributions of intermolecular transfer integrals (t1) at 100 ns for PhC2–BQQDI and PDI–FCN2. The magnitude of the dynamic fluctuations of t1 can be evaluated based on the SD (σ). The effective mass is shown in unit of the rest mass of an electron.

  • Fig. 6 Practical applicability of PhC2–BQQDI SC-TFTs.

    (A) Transfer curves (VD = 30 V) and (B) time-dependent μe and Vth shift (∆Vth) values normalized relative to those in the as-prepared state (μ0 and Vth,0, respectively) acquired during ambient shelf-life tests. Inset in (A) shows a top-view polarized optical micrography image of the TFT. TFT structure: Sub = G = n++-Si; Ins = SiO2 (100 nm) + β–PTS-SAM, Ci = 34.5 nF cm−2; S/D = Au (40 nm). L = 188 μm, W = 216 μm. RH, relative humidity. (C) Schematic summarizing the experimental process. (D) Transfer curves (VD = 50 V) and (E) μe and ∆Vth values normalized relative to those after annealing at 100°C (μ100 and Vth,100, respectively) as a function of annealing temperature (Tanneal). Inset in (D) shows a top-view polarized optical micrography image of the TFT. TFT structure: Sub = polycarbonate (120 μm); G = Au (40 nm); Ins = AL-X601 (260 nm), Ci = 10.2 nF cm−2; S/D = Au (40 nm). L = 98 μm, W = 210 μm. (F) Schematic diagram of the CMOS device. Detailed information about the device structure is given in the Supplementary Materials. (G) Voltage transfer curves obtained from a CMOS inverter. (H) Gate-bias stress values obtained in air for the PhC2−BQQDI TFT having the structure shown in (F).

Supplementary Materials

  • Supplementary Materials

    Robust, high-performance n-type organic semiconductors

    Toshihiro Okamoto, Shohei Kumagai, Eiji Fukuzaki, Hiroyuki Ishii, Go Watanabe, Naoyuki Niitsu, Tatsuro Annaka, Masakazu Yamagishi, Yukio Tani, Hiroki Sugiura, Tetsuya Watanabe, Shun Watanabe, Jun Takeya

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    The PDF file includes:

    • Sections S1 to S9
    • Figs. S1 to S31
    • Tables S1 to S6
    • Legends for movies S1 to S4
    • References

    Other Supplementary Material for this manuscript includes the following:

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