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Reichmanis,
Elsa
Reichmanis,
Elsa
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ItemUtilizing Thiazole and Thioalkyl Side Chains in DPP-based Donor-Acceptor Copolymers for Organic Electronics(Georgia Institute of Technology, 2020-01) Scholz, Audrey ; Khau, Brian ; Buckley, Carolyn ; Reichmanis, ElsaOrganic semiconducting polymers are a popular topic of research for their use in electronics, such as organic field effect transistors (OFETs) and solar cells. Relative to inorganic semiconductors, organic semiconductors have the advantage of higher affordability, improved sustainability, and easier large-scale fabrication. Current research is aimed at developing new donor-acceptor (D-A) polymers with increased stability, charge carrier mobilities, and effective π-π interactions, while limiting the size of bandgaps to optimize the number of excited electrons that can be collected. Previously, we have shown that replacing thiophene with thiazole in diketopyrrolopyrrole (DPP)-based polymers resulted in decreased electron density along the polymer backbone, lowering the HOMO and LUMO levels. This resulted in an increased charge carrier mobility, leading to the design of new DPP-based D-A polymers. To decrease strain and increase stability, the benzodithiophene (BDT) moiety is copolymerized with the DPP unit to form several BDT-DPP donor-acceptor polymers. Specifically, the focus is on substitution of flanking DPP groups to improve planarity across the polymer backbone, which leads to higher effective conjugation and charge carrier mobilities. Furthermore, the incorporation of thioalkyl side chains on the BDT unit could further stabilize the band gap. Initial results show high stability with ionization potentials (Ip) and electron affinities (EA) at approximately 5.91eV and 3.87eV. Intriguingly, these polymers were designed to function as donor materials in solar cells, yet they have demonstrated varying degrees of ambipolarity. With this new development, solar cells will be constructed to ascertain how successfully they function as donors and acceptors.
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ItemSoft, Responsive and Semiconducting Gels(Georgia Institute of Technology, 2018-04-20) Rosu, Cornelia ; Russo, Paul S. ; Reichmanis, ElsaInteraction of biopolymers with organic electronic materials provides an appealing opportunity to design electroactive materials for use in many applications especially bioelectronics. Because of their biocompatibility, polypeptides do not act just as simple bio- components; rather they effectively influence the organization of π-conjugated polymers into highly crystalline structures that allow charge transport. The talk will focus on poly(γ-benzyl-L-glutamate), PBLG, a synthetic polypeptide that forms thermoreversible tree-dimensional networks. Blends with poly(3-hexylthiophene), P3HT, resulted in gel materials able to switch reversibly on and off their photo-physical properties. This behavior was observed during two cycles of heating-cooling-aging. Enhanced alignment of P3HT chains into J-aggregate structures, ideal for effective electronic performance, was attributed to interactions between the PBLG benzyl side chains and P3HT hexyl arms.
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ItemStructure – Process - Property Relationships Governing Solution Processed Semiconductor Performance(Georgia Institute of Technology, 2016-01-26) Reichmanis, ElsaPolymeric semiconductors are promising materials for the commercialization of large‐area, low‐cost and flexible electronics. Their electrical properties are extremely sensitive to structure at multiple length scales, and process modifications can impact calculated hole mobilities by up to four orders of magnitude. For the readily available semiconducting polymer, poly(3‐hexylthiophene) (P3HT), various microstructural features that correlate well with hole mobility have been identified. These include paracrystalline disorder, exciton bandwidth, polymer molecular weight, orientation of crystalline domains, and inter‐grain connectivity. Here, a set of general, robust analysis algorithms will be presented that can be used to statistically quantify two‐dimensional order in microstructures of P3HT‐based OFET devices. Application of these analytical techniques to a variety of shear‐based processing methods indicate that shear‐driven alignment of P3HT fibers can effect substantial improvements in macroscale mobility.
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ItemBIG IDEAS in Sustainability(Georgia Institute of Technology, 2014-03-10) Bras, Bert ; Brown, Marilyn A. ; Crittenden, John C. ; Gardner, John ; Karas, Bruce ; Leffin, Steve ; Reichmanis, Elsa ; Rivenburgh, DianaA celebration of three newly appointed Brook Byers Professors and a candid and casual discussion with these industry and academic leaders on: BIG IDEAS in Sustainability.
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ItemPolymeric Semiconductors: Molecular Ordering, Charge Transport and Macroscale Mobility(Georgia Institute of Technology, 2014-01-28) Reichmanis, ElsaThe performance of devices fabricated using polymeric semiconductors depends critically upon alignment of the polymer chains at the nano- through macro-scales. Significant structure-process- property relationships that allow for enhancement of long-range order will be described. For instance, a lyotropic liquid crystalline (LC) phase has been observed in poly-(3-hexylthiophene) (P3HT) via solvent-evaporation induced self-assembly. In-situ polarized Raman spectroscopy facilitated investigation of the evolution of structure that eventually was found to undergo a phase transition from an isotropic solution to LC phase. The insights gained through these investigations were applied to the design of an alternative, donor-acceptor (D-A) benzothiadiazole oligothiophene based copolymer material. For one family of copolymers, structural elements were found to provide for a span in hole mobility of approximately 3 orders of magnitude. Samples annealed at moderate temperatures exhibited mobilities in excess of 1 cm²/Vs. The lessons learned through these studies may allow for simple, controllable, and cost-effective methodologies for achieving high-performance plastic electronic devices.
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ItemExciton dissociation and charge trapping at poly(3-hexylthiophene)/phenyl-C61-butyric acid methyl ester bulk heterojunction interfaces: Photo-induced threshold voltage shifts in organic field-effect transistors and solar cells(Georgia Institute of Technology, 2012-04) Park, Byoungnam ; You, Nam-Ho ; Reichmanis, ElsaPhotoinduced charge transfer at an electron donor/acceptor interface is one of the most crucial processes in determining the power conversion efficiency of organic solar cell devices. Here, we address exciton dissociation and charge carrier trapping at poly(3-hexylthiophene) (P3HT)/phenyl-C61-butyric acid methyl ester (PCBM) bulk heterojunction interfaces electrically using a field effect transistor (FET). With a P3HT/PCBM composite film, we elucidated exciton dissociation and charge carrier recombination assisted by localized electronic states at the P3HT/PCBM interface via photoinduced threshold voltage shift measurements with respect to wavelength using FETs in combination with organic solar cell devices. Interestingly, the combination of light coupled with a significant quantity of PCBM within the film was required to observe ambipolar charge transport in P3HT/PCBM FETs. This phenomenon was addressed by filling of electron traps associated with PCBM under illumination and formation of the conducting pathways for both electrons and holes. A high density of carrier traps at the interface suggested by the FET results was confirmed in light intensity dependent short-circuit current (Jsc) and open-circuit voltage (Voc) measurements using solar cell devices.
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ItemThe Evolution Study Of Thin Film Structure During The Film Formation(Georgia Institute of Technology, 2010-01) Park, Min Sang ; Aiyar, Avisheck ; Park, Jung Ok ; Reichmanis, Elsa ; Srinivasarao, Mohan