for High-Performance Organic Electronics

65 Figure 3.2.2 Absorption profiles for the polymers (a) in dilute chloroform solution and (b) as. c) Cyclic voltammograms of the polymers. 75 Figure 3.2.13 The AFM phase images of the spin-coated 2ClBT-based polymer films at three.

Technical Terms and Abbreviations

Organic Conjugated Materials: History and Electronic Structure

Historical Context of Organic Semiconductors
Electronic Structure of Organic Semiconductors: π-Conjugation
Conjugated Materials in Resonance Forms
Classification of Conjugated Materials

Oxidative polymerization: Oxidative polymerization can again be divided into two categories in terms of oxidation methods: electrochemical oxidative polymerization and chemical oxidative polymerization. Classification of conjugated materials in terms of major charge carriers and electron affinity.

Structural Elements of Conjugated Materials

Conjugated Backbone
Side Chains
Substituents

Alkyl side chains or alkoxy substituents can further increase the electron-donating properties of the system. In addition to hydrocarbon side chains, side chains containing heteroatoms such as oxygen, fluorine, silicon, etc.

Electronic Applications: Architecture and Principle

Organic Field-Effect Transistor
Organic Photovoltaics

The threshold voltage (VT) increases with impurity concentrations in organic semiconductors, which generates interfacial charge traps in OFETs, as mentioned in an earlier subsection (Operating Principle), and also depends on the gate insulator capacitance and the thickness of the organic film. Consistent with practice, this can provide a measure of the amount of recombination in the device.

Research Progress of Conjugated Materials in Electronic Applications

Research Progress in Organic Field-Effect Transistor System
Research Progress in Organic Photovoltaic System

Finally, the FFs in OPVs are generally influenced by the charge mobility of the materials and morphological factors such as mixing of the two materials. Therefore, in terms of material selection for OPVs, a complementary light absorption of materials, a balance between hole and electron mobility, a gap between energy levels for high VOCs and efficient exciton dissociation have been of interest. considerable to achieve high efficiency OPV.

Research Outline: Understanding of the Relationship between the Structural Elements and Molecular Properties of Organic Conjugated Structural Elements and Molecular Properties of Organic Conjugated

Building Blocks for the Molecular Structural Study
Structural Variations to Control the Properties

Second, the molecular interactions can be controlled by strengthening the noncovalent bond between the building blocks (internal) and conjugated chains (intermolecular) or weakening the molecular rigidity. Thus, by adopting a terpolymer system, the processability of rigid conjugated polymer composed of DPP and TVT can be highly improved.

Theoretical studies of electronic structure and charge transport properties in polythiophene-based organic field-effect transistors. Design and efficient synthesis methods for high performance polymer semiconductors in organic field effect transistors.

Motivation of Energy Level Alignment Study for n-Type Materials

Multiple Blocks for Energy Level Alignment: Understanding of Copolymers Containing Pyridine and Selenophene Simultaneously and

Research Background and the Overview

Synthetic routes and chemical structures of the polymers

Results and Discussions
Conclusion
Supporting Information

DFT-calculated dipole moments (top) and charge density isosurfaces (bottom) of the energy-minimized structures of the trimeric units. The 2D-GIXD images and 1D line cuts of the annealed films in Figure 2.2.5a and Figure 2.2.6 exhibited highly ordered structures of lamellar and π–π stacking with the well-defined multiple lamellar (h00) Bragg peaks from the outside. -of-plane (qz) direction and strong (010) π–π stacking peaks in the in-plane (qxy) direction showing the edge-on dominantly oriented conjugated backbone relative to the substrate. The diffraction peaks became more prominent with stronger intensities as a function of annealing temperature, and the lamellar d-spacings Å) of P1 films were shorter than those of the corresponding P2 films Å) as listed in Table 2.2.9, which is further supported by XRD -the data in figure 2.2.13 and table 2.2.8 (supporting information).

As shown in Figure 2.2.8, P1 devices revealed higher μ over μh regardless of annealing temperature, but P2 devices showed lower μ than μh at 100 °C and 200 °C annealing conditions and improved significantly after annealing at 300 °C. showing the properties of the dominant n-type ambipolar transistor. Electrical Characteristics of P1 OFET Devices without and with NaHCO3 and MoO3 Doping at 200 °C-Annealed Condition. The transfer curves of the modified device and the data are presented in Figure 2.2.9 and Table 2.2.4.

The charge carrier transports of PyDPP-containing and Se-containing polymers in OFET devices

Summary and Conclusion
References
Motivation of Intermolecular Interaction Studies

Highly soluble small molecule organic semiconductor with trihexylsilyloxy side chain for high performance organic field effect transistors with mobility up to 3.10 cm2 V−1 s−1. Importance of solubilizing group and backbone planarity in low band gap polymers for high performance ambipolar field effect transistors. Diketopyrrolopyrrole-based conjugated polymers synthesized via direct arylation polycondensation for high-mobility pure n-channel organic field-effect transistors.

Asymmetric thiophene/pyridine flanked diketopyrrolopyrrole polymers for high performance polymeric ambipolar field effect transistors and solar cells. Effect of Selenophene in DPP Copolymer Incorporating Vinyl Group for High Performance Organic Field Effect Transistors. New n-type polymeric semiconductors based on naphthalene diimide and selenophene derivatives for organic field-effect transistors.

The synthesis procedures of 2ClBT-based polymers

Conclusion
Terpolymer System to Reduce a Backbone Rigidity: Bioderived and Eco-Friendly Solvent-Processed High-Mobility Ambipolar Plastic

Conclusion

Summary and Conclusion
References
Motivation of Resioisomer Studies

Conclusion

Details on the synthesis and molecular characterization of intermediates and polymers can be found in Chapter 7 (Experimental part). Absorption profiles of polymers (a) in dilute chloroform solution and (b) as thin films. c) Cyclic voltammograms of polymers. Transmission (a, b) and output (c, d) curves of optimized polymer OFET devices based on 2ClBT under annealing conditions at 200 °C.

The solubility of the copolymers in CB and MeTHF at room temperature was significantly different by varying the Se content in the backbone, as shown in Figure 3.3.19. Calibration plots of the concentration of CB solutions as a function of absorbance at λmax. Calibration plots of the concentration of MeTHF solutions as a function of the absorbance at the λmax.

Higher charge transport mobility was obtained on the order of the conjugation length of a donor block. The HOMO/LUMO energy levels and orbital distributions on the optimized geometries of the dimers estimated by DFT calculation.

Synthesis routes for preparing intermediates and chemical structures of the polymers

Conclusion

Absorption profiles of the polymers (a) in dilute chloroform solution and (b) as thin films. c) DFT-calculated dipole moments of the dimeric units viewed from above and (d) the HOMO/LUMO distributions. To quantify the crystallite population ratio for edge-on and face-on orientation of the annealed films, we established a pole figure for the (010) reflection peaks, as shown in Figure 4.3.3d. The transfer and output curves for the devices in Figure 4.3.4 and Figure 4.3.14–16 show typical p-type transistor behavior.

The OFET performance trend is similar in the as-cast and annealed film devices, but the properties were improved with thermal treatment of the films at 200 °C for 5 min for all the devices. A more population of the face-on oriented crystallite in P2 may be disadvantageous for the major charge flow direction in OFET devices. Calculated dipole moments and energy levels for the dimeric units of the polymers by DFT.

Summary and Conclusion

To summarize, regioisomeric polymers with hexyl side chains and fluorine withdrawing group were prepared to investigate the difference in intramolecular charge transfer and morphological/microstructural properties by regiochemistry of alkyl chains and substituents with respect to the structure and the optical, electrochemical, morphological and electrical properties in this chapter . In both cases, different regiosymmetric arrangements of the side chains play a critical role in controlling the intrinsic properties of the polymers. Hexyl side chains were attached to a polymer backbone and caused steric hindrance at the adjacent positions, resulting in a distortion of the backbone.

The regioisomeric polymers distorted at different positions showed different optical and morphological properties due to the different type of aggregation and stacking behavior; PI with a severe internal distortion of the donor building blocks showed a parallel type of intermolecular interactions (H-aggregation) and bimodal polymer crystalline packing orientations of a mixed face-up and edge-up stack, which could be beneficial for 3D charge transport. while PO with inter-monomer distortion showed more head-to-tail type aggregation (J-aggregation) and unimodal edge-on dominant molecular packing motif, leading to a different intermolecular charge transport efficiency and a hole mobility of PI twofold greater than that in the PO. Despite the high regioregularity, the distal-proximal alternating configuration of F atoms showed a higher face-up stacking motif than other two, which is perpendicular to the orientation of charge transport from source to drain in bottom gate/bottom contact OFET devices , and thus comparable hole mobility to P1. This finding demonstrates that it is important to find a specific regio-orientation of the asymmetric units in a polymer backbone than simply adopting a regio-regularity for improving OFET performance, which depends on the polymer nature, bulk morphology and OFET performance. determine

High-mobility air-stable naphthalene diimide-based copolymer containing extended π-conjugation for n-channel organic field-effect transistors. Effects of annealing on the nanomorphology and performance of poly(alkylthiophene):fullerene bulk heterojunction solar cells. New donor-donor type copolymers with rigid and coplanar structures for high-mobility organic field-effect transistors.

Timely synthetic adaptation of biaxially extended thienylenevinylene-like polymers for systematic field-effect transistor research. Two-dimensional organic field-effect transistors and solution-processed solar cells based on benzodithiophene and benzothiadiazole. Simplified microwave-assisted preparation of narrow-bandgap conjugated polymers for high-performance bulk heterojunction solar cells.

Summary of the Research

However, the unfavorable distortion effect must be carefully considered in the molecular design step so as not to interfere with intramolecular charge transfer and intermolecular stacking. The 2D–1A terpolymer system significantly improved the solution processability of the polymer by reducing molecular aggregation. Slightly increased lamellar/p-stacking distances, improved lamellar stacking, and finer film surface morphology resulted in increased charge carrier mobility compared to D−A alternating polymers due to optimized features such as improved intermolecular charge transport, interlayer compatibility, and favorable edge-oriented crystalline.

An internal distortion of the donor building blocks resulted in better charge transport properties than that obtained from an intermonomer distortion due to the H-aggregation, high overall crystallinity and greater molecular interconnection. In another regioisomer study with fluorine substituents and three regioisomeric structures, a regioregular type of polymer with F atoms all oriented to the same side exhibited a higher hole mobility than regiorandom and another regioregular isomers with an order of magnitude difference due to the stronger intermolecular interactions and favorable high-order edge-on molecular stacking orientation for source-to-drain charge transport in bottom gate/bottom contact OFET devices. A distal-proximal alternating configuration of F atoms in this research showed a more face-on stacking motif than other two, which can be perpendicular to the entire charge flow direction, resulting in a similar hole mobility with the regiorandom, suggesting that it is important to choose a specific regio-orientation of the asymmetric units in a polymer backbone instead of simply assigning a regularity to improve OFET performance.

Molecular Design Strategies for High-Performance Organic Electronics

Molecular Design for Other Electronic Applications

Quaterpolymer System for Organic Photovoltaics: Densely Packed Random Quaterpolymers Containing Two Donor and Two Acceptor

Conclusion

Details of the synthesis and characterization of the polymers can be found in the Supporting Information. Light absorption profiles of the polymers (a) in dilute chloroform solution and (b) as thin films. c) Cyclic voltammograms of polymers. This indicates that better charge carrier pathways are developed in the active layer of PSCs fabricated from [3-7] and [1-0].

Optical microscopic images of all the blend films in Figure 6.1.15 revealed a homogeneous nature without any crystals or macroscopic defects. Similarly, the TEM image of the [0-1] blend exhibited a large fibrillar structure, while a finer and featureless morphology was found in the other films (Figure 6.1.5b). GIWAXS images of blend films and π–π crystal correlation length (CCL) for the most efficient OPVs and π–π CCL values.