Electrical Characterization Of Polymeric Charge Transport Layers (original) (raw)
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Chemical Physics Letters, 2018
Diketopyrrolopyrrole (DPP) and i-Indigo (i-Ind) are two monomers that are widely explored as active materials in organic field effect transistor and solar cells. These two molecules showed impressive charge carrier mobility due to better packing that are facilitated by quadrupoles. We hypothesized that the copolymers of these monomers would also exhibit high charge carrier mobility. However, we envisioned that the dihedral angle at the connecting point between the monomers will play a crucial role in packing as well as charge transport. To understand the impact of dihedral angle on charge transport, we synthesized three copolymers, wherein the DPP was sandwiched between benzenes, thiophenes and furans. The copolymer of i-Indigo and furan comprising DPP showed a band gap of 1.4 eV with a very high dihedra. The polymer was found to pack better and the coherence length was found to be 112 Å. The hole carrier mobility of these polymer was found to be highest among the synthesized polymer i.e. 0.01 cm 2 /Vs. The copolymer comprising benzene did not transport hole and electrons. The dihedral angle at the connecting point between i-Indigo and benzene DPP was 143 Å , which the packing and consequently charge transport properties.
Development of New Nanostructurally Engineered Polymer Semiconductors for Organic Electronics
2014
The research presented in this thesis was focused on organic semiconductors and has resulted in the development of novel printable polymer semiconductors that can be used in organic thin film transistors (OTFTs) and organic photovoltaics (OPVs), or solar cells. Polymers used in OTFT applications must have particular characteristics, such as a highly ordered or crystalline structure, favoured molecular orientation, and appropriate energy levels for either hole transport (p-type semiconductors) or electron transport (n-type semiconductors). Achieving these properties requires control of the design and synthesis of the polymers through the choice of appropriate building blocks and side chain substituents. In contrast, for OPV applications, the band gap, thin film morphology, and balance of the donor's hole mobility and the acceptor's electron mobility must be finely tuned for optimal photovoltaic performance. The specific focus of the research was on a new type of donor-acceptor copolymers that have alternating electronaccepting azo units and common electron donor units (e.g., thiophene). These polymers are expected to have strong intermolecular interactions due to the donor-acceptor effect, which could lead to improved molecular organization for efficient charge carrier transport in OTFT devices. The donor-acceptor effect also creates narrow band gap polymers, which are preferred for optimum light harvesting. The polymer materials developed in this research are evaluated as channel semiconductors in OTFTs and can also be used as donors in polymer solar cells. Zs discovery of which complemented previous work conducted by the same research group. These innovative building blocks would be valuable in numerous applications, including OTFTs and OPVs. Five polymers have been created, three of which show the most promising potential for OTFT and OPV applications: P1-DTA-BTV, P5-DTAE-BT, and P6-DTAE-TT. All of these copolymers have been synthesized via Stille coupling reaction. The first copolymer, P1-DTA-BTV, which exhibits a small band gap of 1.13 eV, with HOMO and LUMO energy levels of-5.21 eV and-4.08 eV, respectively, is suitable for both OTFT devices and OPV applications. P5-DTAE-BT and P6-DTAE-TT, on the other hand, are characterized by broader band gaps of 1.29 eV and 1.32 eV, respectively, and their average HOMO and LUMO energy levels are-5.43 eV,-4.20 eV, and-5.40 eV,-4.00 eV, respectively. It has been experimentally demonstrated that the presence of an ester group in the (E)-1,2-di(thiazol-2-yl)diazene DTA monomer helps lower the LUMO energy level, creating the broad band gap revealed in the (E)-bis(2-octyldodecyl) 2,2'-(diazene-1,2-diyl)bis(thiazole-4-carboxylate) DTAE copolymer results, and making the P5iv DTAE-BT D-A copolymer an n-type semiconductor, which is very useful for the applications mentioned above. The polymers were characterized by Differential Scanning Calorimetry DSC, Thermal Gravimetric Analysis TGA, Ultraviolet-Visible Spectrometry UV-Vis, Cyclic Voltammetry CV, Atomic Force Microscopy AFM, and X-Ray Diffraction XRD. v I would like to thank my supervisor, Professor Yuning Li, for his encouragement, guidance, and invaluable assistance during my studies. I would also like to express my gratitude to Wei Hong, Chang Guo, and Bin Sun for their help with the characterizations and device performance. Many thanks go to Jesse Quinn, who has had great contributions to some parts of this project and provided extensive assistance in the laboratory. I am likewise very appreciative of my review committee, Professor Neil McManus, and Professor Aiping Yu. A own particular gratitude to my parents specially my father, a natural giver, who encouraged me to complete my studies, as well as to my brothers, Majed and Fahad, who stood by me all the way through my study and challenges, endowing me with love, confidence, and unlimited support. I give heartfelt thanks for my family; to whom I owe more gratitude than I can ever put into words. Among my sincere acknowledgements, the financial support I have received from the Saudi Arabian Ministry of Higher Education is highly appreciated.
Scientific Reports, 2020
In this study, we report an effective approach to tune the crystallization, microstructure and charge transport of solution-processed organic semiconductors by blending with a conjugated polymer additive poly(3-hexylthiophene) (P3HT). When 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) was used as a model semiconductor material to mix with different amount of P3HT, their intermolecular interactions led to distinctive TIPS pentacene film morphologies, including randomly-oriented crystal ribbons, elongated needles with enhanced long-range order, and grass-like curved microwires with interlinkages. Each type of morphology was found to further correlate to considerably different charge transport and device performance. As compared to pristine TIPS pentacene devices, bottom-gate, top-contact OTFTs with 2% in weight P3HT additive showed a 2-fold and 5-fold improvement of average field-effect mobility and performance consistency (defined as the ratio of average mobility to t...
Journal of Physical Organic Chemistry, 2017
New poly-phenylenevinylenes PPVs containing 1,3,4-thiadiazole as candidates for organic semiconductors have been theoretically studied at density functional theory (DFT) and time-dependent DFT levels. This study has been conducted in order to investigate the geometrical and electronic properties as well as the conductivity of a series of PPV-thiophene-1,3,4-thiadiazole-thiophene (H-PhTAT-H) containing-CHO,-CH 2-P(=O)(OCH 3) 2 , and phenyl-CHO (PhCHO) terminal groups. The impact of terminal groups on the optical bandgaps, electron affinity, LUMO energy, and intramolecular reorganization energy was studied for different oligomers and for a limit polymer. The incorporation of terminal groups did not affect the chain length evolution and the vertical transition energy E vert value for a polymer limit compared with the unsubstituted oligomer (H-PhTAT-H). All studied properties showed that CHO-PhTAT-PhCHO and H-PhTAT-H oligomers can be considered as n-type semiconductors.
Molecular Weight Dependent Charge Carrier Mobility in Poly(3,3‘ ‘-dioctyl-2,2‘:5‘,2‘ ‘-terthiophene)
The Journal of Physical Chemistry B, 2006
Poly(3,3′′-dioctyl-2,2′:5′,2′′-terthiophene), a polymer recently used for the fabrication of organic field effect transistors, has been fractionated into five fractions distinctly differing in their molecular weights (M n ), with the goal of determining the influence of the degree of polymerization (DP n ) on its principal physicochemical parameters. It has been demonstrated that within the M n range studied (from 1.5 kDa to 10.5 kDa by SEC), corresponding to DP n from 10 to 38, the polymer band gap steadily decreases with growing molecular weight, which is clearly manifested by an increasing bathochromic shift of the band originating from the π-π* transition. The same trend is observed for the HOMO level, determined from the onset of the p-doping in cyclic voltammetry, which shifts from -5.10 eV to -4.90 eV for the lowest and the highest molecular weight fractions, respectively. The most pronounced influence of DP n has been found for the charge carriers' mobilitys one of the most important parameters of field effect transistors (FETs) fabricated from this polymer. A fourfold increase in DP n results in an increase of the carriers' mobility by more than 3 orders of magnitude. Comparison of these results with those obtained for fractionated regioregular poly(3-hexylthiophene) shows a strikingly similar behavior of both polymers with respect to the molecular weight.
Applied Physics Letters, 2006
This work presents an organic thin film transistor using double polymer layers, polymer electrolyte/ conjugated polymer, i.e., poly͑diallyldimethylammonium chloride͒ ͑PDDA͒/poly͑diphenylamine͒ ͑PDPA͒ structure. The single mobile anions ͑Cl − ͒ pending on the PDDA are stuffed into the conjugated polymer to dope the nitrogen atoms ͑imine͒ by applying the gate bias, resulting a higher drain current under the same source-drain voltage. The PDDA/PDPA polymer structure working in the enhancement mode which operates under atmospheric conditions as a typical p-channel transistor is demonstrated.