Naphthalene Diimide Polymers Research Articles

Nanoimprint Lithography Facilitated Plasmonic‐Photonic Coupling for Enhanced Photoconductivity and Photocatalysis

AbstractImprint lithography has emerged as a reliable, reproducible, and rapid method for patterning colloidal nanostructures. As a promising alternative to top‐down lithographic approaches, the fabrication of nanodevices has thus become effective and straightforward. In this study, a fusion of interference lithography (IL) and nanosphere imprint lithography on various target substrates ranging from carbon film on transmission electron microscope grid to inorganic and dopable polymer semiconductor is reported. 1D plasmonic photonic crystals are printed with 75% yield on the centimeter scale using colloidal ink and an IL‐produced polydimethylsiloxane stamp. Atomically smooth facet, single‐crystalline, and monodisperse colloidal building blocks of gold (Au) nanoparticles are used to print 1D plasmonic grating on top of a titanium dioxide (TiO2) slab waveguide, producing waveguide‐plasmon polariton modes with superior 10 nm spectral line‐width. Plasmon‐induced hot electrons are confirmed via two‐terminal current measurements with increased photoresponsivity under guiding conditions. The fabricated hybrid structure with Au/TiO2 heterojunction enhances photocatalytic processes like degradation of methyl orange (MO) dye molecules using the generated hot electrons. This simple colloidal printing technique demonstrated on silicon, glass, Au film, and naphthalenediimide polymer thus marks an important milestone for large‐scale implementation in optoelectronic devices.

Comparison of two side-chain design strategies for indacenodithienothiophene–naphthalene diimide polymer photovoltaic acceptors prepared by direct (hetero)arylation polycondensation

Two new indacenodithienothiophene–naphthalene diimide polymer acceptors PIN-1 and PIN-2 are rationally designed by two side-chain design strategies (SE-2 and SE-3) and are synthesized by the direct (hetero)arylation polycondensation (DHAP) method.

Poly(2,2’-(2,5-difluoro-1,4-phenylene)dithiophene-alt-naphthalene diimide) synthesized by direct (hetero)arylation reaction for all-polymer solar cells

The weak donor-strong acceptor polymer acceptors for all-polymer solar cells (all-PSCs) have gained much less attention compared with the typical donor-strong acceptor counterparts. Direct (hetero)arylation polymerization reaction is a rising synthetic method, although most of the naphthalene diimide polymer photovoltaic acceptors have been prepared by classic Stille polymerization. A weak donor-strong acceptor polymer acceptor PNB2F has been successfully designed and synthesized by the two-step direct (hetero)arylation reaction and further applied in all-PSCs. The all-PSC device based on PNB2F and electron-donating polymer PBDB-T gained a PCE of 4.49%. The results demonstrate that direct (hetero)arylation reaction is a promising tool for building efficient polymer acceptors with convenient and low-cost synthesis ideas. • The polymer acceptor PNB2F has been successfully synthesized by a convenient two-step direct (hetero)arylation reaction. • PNB2F is a weak donor-strong acceptor polymer acceptor, which has gained much less attention compared with the typical donor-strong acceptor counterparts. • The PBDB-T: PNB2F based all-PSCs achieves a PCE of 4.49%.

Electron transport in a sequentially doped naphthalene diimide polymer

Sequential doping of PNBS, notably with (N-DMBI)2, is studied using UV-vis.-NIR spectroscopy, GIXRD, and variable-temperature conductivity measurements.

Small Band gap Boron Dipyrromethene-Based Conjugated Polymers for All-Polymer Solar Cells: The Effect of Methyl Units

Naphthalene diimide (NDI)-based conjugated polymers have been widely used as the nonfullerene electron acceptor for all-polymer solar cells (all-PSCs), but their low absorption coefficient in the near-infrared (NIR) region severely limits the light harvesting ability in solar cells and hence lowers their photovoltaic performance. In this work, two narrow band gap donor–acceptor conjugated polymers based on boron dipyrromethene (BODIPY) as the electron-deficient unit were developed as the electron donor to combine with a NDI-polymer acceptor in order to significantly improve the photoresponse in the NIR region. More importantly, we found that methyl substitution on the BODIPY segment played an important role in charge transport in these polymers. When methyl units were attached to the α-position of BODIPY, the polymer PMBBDT exhibited high-lying energy levels, improved crystallinity, and dramatically high hole mobility compared to the polymer PBBDT without methyl substitution. Consequently, the power conversion efficiencies (PCEs) could be enhanced from 0.32% for PBBDT- to 5.8% for PMBBDT-based all-PSCs, and the photoresponse covered from 300 to 900 nm. Our results demonstrate that methyl-substituted BODIPY-based conjugated polymers are promising candidates to solve the NIR absorption issue in NDI polymers and, therefore, can be potentially used to further boost the PCEs of all-PSCs similar with organic solar cells based on NIR-fused ring electron acceptors.

Effect of Backbone Sequence of a Naphthalene Diimide-Based Copolymer on Performance in n-Type Organic Thin-Film Transistors.

We report two newly synthesized naphthalene diimide (NDI)-based conjugated polymers, poly[(E)-2,7-bis(2-decyltetradecyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone-vinylene-thiophene-vinylene] (PNDI-VTV) and poly[(E)-2,7-bis(2-decyltetradecyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone-vinylene-selenophene-vinylene] (PNDI-VSV) with different donor units as electron-transporting organic semiconductors for organic field-effect transistors (OFETs). Furthermore, we study the effect of vinylene position on electron transport in the NDI polymers by using two similar polymers but with thiophene-vinylene-thiophene (PNDI-TVT) instead of vinylene-thiophene-vinylene or selenophene-vinylene-selenophene (PNDI-SVS) instead of vinylene-selenophene-vinylene. By incorporating vinylene between thiophene (or selenophene) units, the resulting NDI-based polymers PNDI-VTV and PNDI-VSV show larger backbone planarity than PNDI-TVT and PNDI-SVS. The polymers with a shorter acceptor monomer unit (PNDI-VTV and PNDI-VSV) show a strong face-on orientation, whereas those with a longer monomer unit (PNDI-TVT and SVS) exhibit a mixed face-on and edge-on orientation by two-dimensional grazing incidence X-ray diffraction. Optimized PNDI-VTV and PNDI-VSV OFETs exhibit electron mobilities of 0.043 and 0.7 cm2/(V·s), which is quite lower than those of PNDI-TVT and PNDI-SVS. In addition, the activation energies for electron transport of PNDI-VTV and PNDI-VSV were larger than those of PNDI-TVT and PNDI-SVS. Overall, this research provides the insight that the molecular alignment on the substrate can be controlled by the sequence of rigid acceptor monomer molecules for improving the electron transport of NDI polymers.

Bandgap Engineering of Dual Acceptor-Containing Naphthalene Diimide Polymers for All-Polymer Solar Cells

Naphthalene diimide (NDI)-based polymers, as nonfullerene acceptors for all-polymer solar cells (all-PSCs), are usually investigated by manipulating electron-donating units, which have a narrow ban...

Drastic Improvement of Air Stability in an n-Type Doped Naphthalene-Diimide Polymer by Thionation.

Organic thermoelectrics are attractive for the fabrication of flexible and cost-effective thermoelectric generators (TEGs) for waste heat recovery, in particular by exploiting large-area printing of polymer conductors. Efficient TEGs require both p- and n-type conductors: so far, the air instability of polymer n-type conductors, which typically lose orders of magnitude in electrical conductivity (σ) even for short exposure time to air, has impeded processing under ambient conditions. Here we tackle this problem in a relevant class of electron transporting, naphthalene-diimide copolymers, by substituting the imide oxygen with sulfur. n-type doping of the thionated copolymer gives rise to a higher σ with respect to the non-thionated one, and most importantly, owing to a reduced energy level of the lowest-unoccupied molecular orbital, σ is substantially stable over 16 h of air exposure. This result highlights the effectiveness of chemical tuning to improve air stability of n-type solution-processable polymer conductors and shows a path toward ambient large-area manufacturing of efficient polymer TEGs.

Anion-induced N-doping of naphthalenediimide polymer semiconductor in organic thin-film transistors

Molecular doping is an important strategy to improve the charge transport properties of organic semiconductors in various electronic devices. Compared to p-type dopants, the development of n-type dopants is especially challenging due to poor dopant stability against atmospheric conditions. In this article, we report the n-doping of the milestone naphthalenediimide-based conjugated polymer P(NDI2OD-T2) in organic thin film transistor devices by soluble anion dopants. The addition of the dopants resulted in the formation of stable radical anions in thin films, as confirmed by EPR spectroscopy. By tuning the dopant concentration via simple solution mixing, the transistor parameters could be readily controlled. Hence the contact resistance between the electrodes and the semiconducting polymer could be significantly reduced, which resulted in the transistor behaviour approaching the desirable gate voltage-independent model. Reduced hysteresis was also observed, thanks to the trap filling by the dopant. Under optimal doping concentrations the channel on-current was increased several fold whilst the on/off ratio was simultaneously increased by around one order of magnitude. Hence doping with soluble organic salts appears to be a promising route to improve the charge transport properties of n-type organic semiconductors.

N-Phenyl naphthalene diimide pendant polymer as a charge storage material with high rate capability and cyclability

Abstract

Rylene diimide and dithienocyanovinylene copolymers for polymer solar cells

Two polymers containing (E-2,3-bis(thiophen-2-yl)acrylonitrile (CNTVT) as a donor unit, perylene diimide (PDI) or naphthalene diimide (NDI) as an acceptor unit, are synthesized by the Stille coupling copolymerization, and used as the electron acceptors in the solution-processed organic solar cells (OSCs). Both polymers exhibit broad absorption in the region of 300–850 nm. The LUMO energy levels of the resulted polymers are ca.–3.93 eV and the HOMO energy levels are–5.97 and–5.83 eV. In the binary blend OSCs with PTB7-Th as a donor, PDI polymer yields the power conversion efficiency (PCE) of up to 1.74%, while NDI polymer yields PCE of up to 3.80%.

Naphthalenediimide Polymers with Finely Tuned In-Chain π-Conjugation: Electronic Structure, Film Microstructure, and Charge Transport Properties.

Naphthalenediimide-based random copolymers (PNDI-TVTx) with different π-conjugated dithienylvinylene (TVT) versus π-nonconjugated dithienylethane (TET) unit ratios (x = 100→0%) are investigated. The PNDI-TVTx-transistor electron/hole mobilities are affected differently, a result rationalized by molecular orbital topologies and energies, with hole mobility vanishing but electron mobility decreasing only by ≈2.5 times when going from x = 100% to 40%.

Improved electron transport properties of n-type naphthalenediimide polymers through refined molecular ordering and orientation induced by processing solvents.

To determine the role played by the choice of processing solvents in governing the photophysics, microstructure, and charge carrier transport in naphthalenediimide (NDI)-based polymers, we have prepared two new NDI-bithiophene (T2)- and NDI-thienothiophene (TTh)-containing polymers with hybrid siloxane pentyl chains (SiC5) (P(NDI2SiC5-T2) and P(NDI2SiC5-TTh)). Among the various processing solvents studied here, the films prepared using chloroform exhibited far better electron mobilities (0.16 ± 0.1-0.21 ± 0.05 cm(2) V(-1) s(-1)) than the corresponding samples prepared from different solvents, exceeding one order of magnitude higher, indicating the significant influence of the processing solvent on the charge transport. Upon thin-film analysis using atomic force microscopy and grazing incidence X-ray diffraction, we discovered that molecular ordering and orientation are affected by the choice of the processing solvent, which is responsible for the change in the transport characteristics of this class of polymers.

Perylene and naphthalene diimide polymers for all-polymer solar cells: a comparative study of chemical copolymerization and physical blend

Five copolymers, having 4,4,9,9-tetrakis(4-hexylphenyl)-indaceno[1,2-b:5,6-b′]-dithiophene as a donor unit, and perylene diimide (PDI) and/or naphthalene diimide (NDI) as acceptor moieties, were synthesized, and used as electron acceptors in polymer solar cells.

Cyclopentadithiophene–naphthalenediimide polymers; synthesis, characterisation, and n-type semiconducting properties in field-effect transistors and photovoltaic devices

The synthesis, characterisation, and device performance of a series of cyclopentadithiophene (CPDT)-naphthalenediimide (NDI) donor-acceptor-donor (D-A-D) polymers is reported. The monomers with various alkyl chains are synthesised via direct arylation using palladium complex catalyst. The monomers are then polymerised by oxidative polymerisation using FeCl3 to provide high molecular weight polymers (Mn = 21,800–76,000). The polymer films show deep-red absorption including near-infrared region up to 1100 nm to give optical bandgap of approximately 1.16 eV. The polymers exhibit only n-type semiconducting properties giving the highest electron mobility of 9 × 10-3 cm2 V−1 s−1 in organic field-effect transistors (OFETs). Organic photovoltaic (OPV) devices are fabricated from solutions of the polymers as acceptors and poly(3-hexylthiophene) (P3HT) as a donor.

Synthesis and characterization of naphthalene diimide polymers based on donor-acceptor system for polymer solar cells

Three donor-acceptor (D-A) naphthalene diimide copolymers, poly{thieno(3,2-b)thiophene-diyl-alt-N,N!-bis(2- octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)}(P1), poly{4,8-dioctyloxybenzo(1,2-b;3,4-b!)dithiophene-diyl-alt- N,N!-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)}(P2), and poly{4,8-bis(2-ethylhexyloxy)benzo(1,2- b:4,5-b!)dithiophene-diyl-alt-N,N!-bis(2-octyldodecyl) -naphthalene-1,4,5,8-bis(dicarboximide)}(P3), were synthesized by Stille coupling reaction. All copolymers showed good solubility in common organic solvents with broad absorption region and narrow optical band gap. The electrochemical properties of the polymers can be adjusted by changing the donor seg- ment. P1 showed n-type characteristic while P2 and P3 showed p-type characteristic. All-polymer solar cells using P3HT as the donor and P1 as the acceptor were fabricated and the highest power conversion efficiencies (PCEs) of 0.068% were obtained under the preliminary condition. Moreover, p-type naphthalene diimide copolymers (P2 and P3) based on D-A system were used as donors to fabricate bulk heterojunction polymer solar cells (BHJ, PSCs) for the first time, and the max- imum power conversion efficiencies PCEs were about 0.021 and 0.017%, respectively.

Synthesis and Characterization of Thiophene-Containing Naphthalene Diimide n-Type Copolymers for OFET Applications

Naphthalene diimide (NDI) copolymers are attractive n-type materials for use in organic electronic devices. Four highly soluble NDI polymers are presented—each differing only in the thiophene content comprising the material. Electron mobilities as high as 0.076 cm2 V−1 s−1 for the novel material PNDI-3Th are reported. Polymer crystallinity and general macromolecular order are shown to effectively improve by increasing the number of thiophene units within the polymer backbone. The structure−property relationship of NDI−thiophene copolymers is presented and discussed as it pertains to organic field effect transistor (OFET) performance.