Correlating charge transport to structure in deconstructed diketopyrrolopyrrole oligomers: A case study of a monomer in field-effect transistors

Copolymers based on diketopyrrolopyrrole (DPP) cores have attracted a lot of attention because of their high p-type as well as n-type carrier mobilities in organic field-effect transistors (FETs) and high power conversion efficiencies in solar cell structures. We report the structural and charge transport properties of n-dialkyl side-chain-substituted thiophene DPP end-capped with a phenyl group (Ph-TDPP-Ph) monomer in FETs which were fabricated by vacuum deposition and solvent coating. Grazing-incidence X-ray diffraction (GIXRD) from bottom-gate, bottom-contact FET architectures was measured with and without biasing. Ph-TDPP-Ph reveals a polymorphic structure with pi-conjugated stacking direction oriented in-plane. The unit cell comprises either one monomer with a = 20.89 angstrom, b = 13.02 angstrom, c = 5.85 angstrom, alpha = 101.4 degrees, beta = 90.6 degrees, and gamma = 94.7 degrees for one phase (TR1) or two monomers with a = 24.92 angstrom, b = 25.59 angstrom, c = 5.42 angstrom, alpha = 80.3 degrees, beta = 83.5 degrees, and gamma = 111.8 degrees for the second phase (TR2). The TR2 phase thus signals a shift from a coplanar to herringbone orientation of the molecules. The device performance is sensitive to the ratio of the two triclinic phases found in the film. Some of the best FET performances with p-type carrier mobilities of 0.1 cm(2)/V s and an on/off ratio of 10(6)are for films that comprise mainly the TR1 phase. GIXRD from in operando FETs demonstrates the crystalline stability of Ph-TDPP-Ph

Human telomeres that carry an integrated copy of human herpesvirus 6 are often short and unstable, facilitating release of the viral genome from the chromosome

Linear chromosomes are stabilized by telomeres, but the presence of short dysfunctional telomeres triggers cellular senescence in human somatic tissues, thus contributing to ageing. Approximately 1% of the population inherits a chromosomally integrated copy of human herpesvirus 6 (CI-HHV-6), but the consequences of integration for the virus and for the telomere with the insertion are unknown. Here we show that the telomere on the distal end of the integrated virus is frequently the shortest measured in somatic cells but not the germline. The telomere carrying the CI-HHV-6 is also prone to truncations that result in the formation of a short telomere at a novel location within the viral genome. We detected extra-chromosomal circular HHV-6 molecules, some surprisingly comprising the entire viral genome with a single fully reconstituted direct repeat region (DR) with both terminal cleavage and packaging elements (PAC1 and PAC2). Truncated CI-HHV-6 and extra-chromosomal circular molecules are likely reciprocal products that arise through excision of a telomere-loop (t-loop) formed within the CI-HHV-6 genome. In summary, we show that the CI-HHV-6 genome disrupts stability of the associated telomere and this facilitates the release of viral sequences as circular molecules, some of which have the potential to become fully functioning viruses

Donor-acceptor copolymers and sol-gel processable zinc oxide for thin film transistors and hybrid photodetectors

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Organic semiconductors have been gaining attention both in research and commercial development for electronic devices due to their low manufacturing and processing costs. Copolymers based on diketopyrrolopyrrole (DPP) cores have attracted a lot of attention due to their high p-type as well as n-type carrier mobilities in organic field-effect transistors (FETs) and high power conversion efficiencies in solar cell structures. Hybrid organic-inorganic photodiode interfaces have also gained significant interest due to the realization of intrinsic p-n junctions as well as their unique physical properties such as mechanical flexibility and high photosensitivity. ZnO is an intrinsic n-type semiconductor which is non-toxic and sol-gel processable, creating avenues for film patterning and fully solution processed devices. In this work, we report the structural and charge transport properties of n-dialkyl side-chain substituted thiophene DPP end-capped with a phenyl group (Ph-TDPP-Ph) monomer in FETs which were fabricated by vacuum deposition and solvent casting. From grazing incidence X-ray diffraction (GIXRD), Ph-TDPP-Ph reveals polymorphic structure with [pi]-conjugated stacking direction oriented in-plane. The unit cell comprises either one monomer for one phase (TR1), or two monomers for the second phase (TR2). The TR2 phase thus signals a shift from a coplanar to herringbone orientation of the molecules. The device performance is sensitive to the ratio of the two triclinic phases found in the film. Some of the best FET performances with p-type carrier mobilities of 0.1 cm2/Vs and on/off ratio of 10[superscript 6] are for films that comprise mainly the TR1 phase.Includes bibliographical reference

Hybrid ZnO-organic semiconductor interfaces in photodetectors: A comparison of two near-infrared donor-acceptor copolymers

Hybrid organic-inorganic photodiode interfaces have gained significant interest due to their unique physical properties such as mechanical flexibility and high photosensitivity. Two diketopyrrolopyrrole (DPP)-based donor-acceptor copolymers with different backbone conformations are characterized in an inverted non-fullerene photodiode architecture using ZnO nano-patterned films as the electron transport layer. The DPP copolymer with a thienothiophene unit (PBDT-TIDPP) is more planar and rigid compared to the DPP system with a thiophene unit connecting the donor and acceptor moieties within the monomer (PBDT-TDPP). The hybrid interfaces were optimized by using poly(3-hexylthiophene) (P3HT) as the p-type layer for monitoring the critical thickness and morphology of the ZnO layer. The maximum photoresponsivity from a P3HT:ZnO photodiode was found to be 56 mA/W. The photoresponsivity of PBDT-TTDPP:ZnO photodiodes were found to be more than two orders of magnitude higher than PBDT-TDPP:ZnO photodiodes, which is attributed to an enhanced transport of carriers due to the planar backbone conformation of the PBDT-TTDPP copolymer. Capacitance-voltage measurements from hybrid Schottky barrier interfaces further shed light into the nature of photocarriers and device parameters. First-principles time-dependent density-functional theoretical calculations yield a higher absorptivity for the PBDT-TTDPP dimer compared to PBDT-TDPP. (C) 2017 Elsevier B.V. All rights reserved

Correlating Charge Transport with Structure in Deconstructed Diketopyrrolopyrrole Oligomers: A Case Study of a Monomer in Field-Effect Transistors

Copolymers based on diketopyrrolopyrrole (DPP) cores have attracted a lot of attention because of their high p-type as well as n-type carrier mobilities in organic field-effect transistors (FETs) and high power conversion efficiencies in solar cell structures. We report the structural and charge transport properties of <i>n</i>-dialkyl side-chain-substituted thiophene DPP end-capped with a phenyl group (Ph-TDPP-Ph) monomer in FETs which were fabricated by vacuum deposition and solvent coating. Grazing-incidence X-ray diffraction (GIXRD) from bottom-gate, bottom-contact FET architectures was measured with and without biasing. Ph-TDPP-Ph reveals a polymorphic structure with π-conjugated stacking direction oriented in-plane. The unit cell comprises either one monomer with <i>a</i> = 20.89 Å, <i>b</i> = 13.02 Å, <i>c</i> = 5.85 Å, α = 101.4°, β = 90.6°, and γ = 94.7° for one phase (TR1) or two monomers with <i>a</i> = 24.92 Å, <i>b</i> = 25.59 Å, <i>c</i> = 5.42 Å, α = 80.3°, β = 83.5°, and γ = 111.8° for the second phase (TR2). The TR2 phase thus signals a shift from a coplanar to herringbone orientation of the molecules. The device performance is sensitive to the ratio of the two triclinic phases found in the film. Some of the best FET performances with p-type carrier mobilities of 0.1 cm²/V s and an on/off ratio of 10⁶ are for films that comprise mainly the TR1 phase. GIXRD from in operando FETs demonstrates the crystalline stability of Ph-TDPP-Ph