New semi-crystalline photovoltaic polymers were synthesized and the optimized device exhibited 9.39% efficiency in a ∼300 nm thick single-cell device.

We report a series of benzotriazole-based semicrystalline π-conjugated polymers with noncovalent conformational locks for applications in polymer field-effect transistors. The benzotriazole moiety is a versatile electron-deficient building block that offers two chemically functionalizable sites, 2(N) and 5, 6(C) positions, allowing easy modulation of the solution processability and electronic structures of the resulting polymers. Fluorine or alkoxy substituents were introduced to the benzotriazole unit to enhance the molecular ordering through intra- and intermolecular F···S, F···H–C, C–F···πF, or S···O attractive interactions. The fluorinated polymer (PTBTz-F) showed remarkably enhanced hole mobility (μh = 1.9 cm2/(V·s), on/off ratio = 8 × 107) upon thermal annealing at 305 °C, compared to the unsubstituted one (PTBTz) (μh = 7.0 × 10–3 cm2/(V·s), on/off ratio = 3 × 106). Alkoxy unit substitution (PTBTz-OR) also improved the carrier mobility up to 0.019 cm2/(V·s) with an on/off ratio of 4 × 105. Fluorine or alkoxy substitution induced tight interchain ordering with edge-on orientation, as confirmed by X-ray diffraction measurements. In particular, fluorinated PTBTz-F showed high thermal stability (T d 453 °C) and the remarkable device characteristics with deep frontier orbital levels.

Thiophene- and thienothiophene-based donor–acceptor (D–A) type semicrystalline copolymers with different backbone curvatures, PTBT14 and PTTBT14, were designed and synthesized. Both the polymers exhibit a nearly planar structure via noncovalent S···O and C–H···N attractive interactions, etc., in the polymer chain. PTTBT14 is linear, whereas PTBT14 is curved owing to ∼160° bond angle of the thiophene linkage. PTTBT14 showed the higher degree of interchain ordering with edge-on orientation, resulting in efficient charge transport (0.26 cm2 V–1 s–1 for PTTBT14 compared to 0.02 cm2 V–1 s–1 for PTBT14) in PFETs with remarkable morphological stability and no deterioration in device properties at temperatures up to 250 °C. On the other hand, the curved shape of PTBT14 attributed to its improved photovoltaic properties with a power conversion efficiency of 5.56%. The linear PTTBT14 showed much stronger self-interactions with negligible morphological changes and little miscibility with PC61BM, showing the poor photovoltaic characteristics.

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A series of thienothiophene-benzotriazole-based semicrystalline copolymers, PTTBTz, PTTBTz-F, and PTTBTz-OR, were synthesized by considering chain linearity, planarity and inter-chain packing by virtue of non-covalent attractive interaction. Fluorine and alkoxy substituents were introduced to modulate the intra-and inter-chain coulombic interactions and crystalline ordering. The fluorine and alkoxy-substituted PTTBTz-F and PTTBTz-OR showed pronounced inter-chain packing with edge-on orientation confirmed by UV-vis absorption and X-ray diffraction measurements. The well-resolved diffraction patterns were obtained for PTTBTz-F and PTTBTz-OR, showing (100)∼(500) inter-lamellar scattering peaks (d-spacing, 17∼18 Å) in the out-of-plane direction and a π-π stacking peak (d-spacing, 3.5∼4.1 Å) in the in-plane direction. Organic field effect transistor (OFET) devices were fabricated with a bottom gate and top contact geometry. PTTBTz-F (μ h = 4.49 × 10 -2 cm 2 V -1 s -1 , on/off ratio = 1.13 × 10 7 ) and PTTBTz-OR (μ h = 8.39 × 10 -3 cm 2 V -1 s -1 , on/off ratio = 2.98 × 10 4 ) showed nearly 3 and 2 orders of magnitude higher hole mobility upon annealing at 305 and 260 °C, with compared to the unsubstituted PTTBTz.

A semicrystalline low-bandgap polymer (PDTPBT) based on alternating dithienopyrrole and benzothiadiazole moieties as a pair of the indene-C 60 bisadduct (ICBA) for polymeric solar cells is reported. The lowest unoccupied molecular orbital (LUMO) level of PDTPBT is measured to be −3.47 eV, ensuring suffi cient energy offset for photoinduced charge transfer to ICBA. Photovoltaic cells are fabricated with ICBA and [6,6]-phenyl-C 71 -butyric acid methyl ester (PC 71 BM) as an acceptor. By replacing PC 71 BM with ICBA, the open-circuit voltage is increased by 0.23 V and the resulting power conversion efficiency is improved from 1.17% to 1.71%. To optimize the ICBAbased devices, crystalline low-bandgap structures should be designed carefully as a pair of ICBA by considering the energy-level offset for charge separation and crystalline interchain ordering, for minimizing the intercalated ICBAs inside the polymer domain. [+] These authors contributed equally to this work. studied extensively for applications in organic electronic and optoelectronic devices. [1][2][3][4] Considerable effort has been made to unveil the structure-properties relationships to fi ne-tune the electronic structure of conjugated polymers and optimize the device characteristics. [4][5][6][7] Recently, bulk heterojunction (BHJ) polymeric solar cells (PSCs), consisting of conjugated polymers (as a donor) mixed with C60 or C70 fullerene derivatives (as an acceptor), have shown promising performance with a power conversion efficiency (PCE) of more than ≈8%. [8][9][10][11][12][13][14][15] The structure studied most thoroughly is poly(3-hexylthiophene) (P3HT), which has shown a PCE of 4%-6.5% by optimizing the material structure (i.e., stereoregularity, etc.) and device architecture. [16][17][18][19][20][21] In particular, the incorporation of an indene-C 60 bisadduct (ICBA) has improved the PCE of P3HT-based PSCs substantially. ICBA has a higher lowest unoccupied molecular orbital (LUMO) (ca. −3.7 eV) than [6,6]-phenyl-C 61 (or C 71 )-butyric

A series of oligothiophenes containing thienopyrroledione with rhodanine, dicyanovinyl and octylcyanoacrylate end-capping groups are explored with two alkyl chain topologies.

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