Anisotropic Polaron Delocalization in Conjugated Homopolymers and Donor–Acceptor Copolymers

Ghosh, Raja; Luscombe, Christine K.; Hambsch, Mike; Mannsfeld, Stefan C. B.; Salleo, Alberto; Spano, Frank C.

doi:10.1021/acs.chemmater.9b01704

Cited by 52 publications

(157 citation statements)

References 76 publications

Supporting

Mentioning

147

Contrasting

Order By: Relevance

“…Electronic absorption spectroscopy is widely utilized for the characterization of doped polymeric semiconductors owing to the facile investigation of the subgap optical absorptions from the polaronic species. Polaronic species generated after doping of conjugated polymers were reported to be delocalized in 1D (intrachain) or 2D (interchain) depending on the molecular order present in the system under investigation 3,51,52 . Therefore, polarized absorption spectroscopy conducted on oriented polymeric films and their subsequent doping are expected to provide significant information regarding the nature of the delocalized polaron in such systems.…”

Section: Resultsmentioning

confidence: 99%

Ordered arrangement of F4TCNQ anions in three-dimensionally oriented P3HT thin films

Nagamatsu

Pandey

2020

Sci Rep

View full text Add to dashboard Cite

An ordered arrangement of electron-accepting molecular dopant, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), in three-dimensionally (3D) oriented poly(3-hexylthiophene) (P3HT) film was clarified. The 3D oriented P3HT thin films prepared by the friction-transfer technique were doped with F4TCNQ by dipping into an acetonitrile solution. The presence of F4TCNQ anions in the 3D oriented P3HT thin films was investigated by polarized ultraviolet/visible/near-infrared absorption spectroscopy, grazing incidence X-ray diffractometry, polarized Fourier transform infrared spectroscopy (FT-IR), and infrared p-polarized multiple-angle incidence resolution spectroscopy (pMAIRS). The F4TCNQ-doped 3D oriented P3HT films showed anisotropic properties in all characterizations. In particular, the anisotropic molecular vibrations from polarized FT-IR and pMAIRS have clearly revealed orientations of polymeric chains and molecular dopant molecules. Considering the results from several independent techniques indicated that F4TCNQ anions in the 3D oriented P3HT were orderly arranged in a 3D manner with respect to the 3D oriented P3HT such that their molecular long-axis parallel to the P3HT backbone, with in-plane molecular orientation. Additionally, the direction of the optical transition moment of the F4TCNQ anion was found to be parallel to the molecular short-axis.

show abstract

Section: Resultsmentioning

confidence: 99%

Ordered arrangement of F4TCNQ anions in three-dimensionally oriented P3HT thin films

Nagamatsu

Pandey

2020

Sci Rep

View full text Add to dashboard Cite

show abstract

“…It is now well established that the position and shape of the P1 absorption band reflects the degree of delocalization of the polarons, with redder absorption corresponding to more delocalization/less Coulomb binding and vice-versa for bluer P1 absorption. [5][6][7][8][9]26,[59][60][61] In previous work, we used ultrafast spectroscopy to show that for P3HT doped with F 4 TCNQ, the growth of the blue shoulder at higher doping concentrations was indicative of a population of trapped carriers that appears only after the polymer crystallites are full. [45] We will argue below that this picture also holds true for the DDB dopants, and that dopants in conjugated polymers preferentially occupy the lamellar regions of their crystallites, when possible.…”

Section: Optical and Electrical Properties Of Ddb-doped P3ht Filmsmentioning

confidence: 99%

“…[5][6][7][8][9]26,27,46,[59][60][61] In particular, the more delocalized the polaron, the more red-shifted the main P1 absorption band (0.3-0.6 eV) and the higher the relative intensities of the so-called "IRAV" band near 0.15 eV. [5,6,8,9] In previous work from our group investigating the use of DDB-F 72 as a dopant, we observed a red-shifted P1 absorption and higher IRAV absorption intensity, indicating this anion was positioned to be greater than 1 nm from the polaron, something that is never seen with small-molecule dopants like F 4 TCNQ. [6] Indeed, a recent theoretical analysis by Ghosh et al suggests that the DDB-F 72 dopant produces some of the most delocalized polarons ever observed on chemically doped P3HT.…”

Section: Degree Of Polaron Localization Following Doping Of P3ht Withmentioning

confidence: 99%

Tunable Dopants with Intrinsic Counterion Separation Reveal the Effects of Electron Affinity on Dopant Intercalation and Free Carrier Production in Sequentially Doped Conjugated Polymer Films

Aubry

Winchell

Salamat

et al. 2020

Adv Funct Materials

View full text Add to dashboard Cite

Carrier mobility in doped conjugated polymers is limited by Coulomb interactions with dopant counterions. This complicates studying the effect of the dopant's oxidation potential on carrier generation because different dopants have different Coulomb interactions with polarons on the polymer backbone. Here, dodecaborane (DDB)-based dopants are used, which electrostatically shield counterions from carriers and have tunable redox potentials at constant size and shape. DDB dopants produce mobile carriers due to spatial separation of the counterion, and those with greater energetic offsets produce more carriers. Neutron reflectometry indicates that dopant infiltration into conjugated polymer films is redox-potential-driven. Remarkably, X-ray scattering shows that despite their large 2-nm size, DDBs intercalate into the crystalline polymer lamellae like small molecules, indicating that this is the preferred location for dopants of any size. These findings elucidate why doping conjugated polymers usually produces integer, rather than partial charge transfer: dopant counterions effectively intercalate into the lamellae, far from the polarons on the polymer backbone. Finally, it is shown that the IR spectrum provides a simple way to determine polaron mobility. Overall, higher oxidation potentials lead to higher doping efficiencies, with values reaching 100% for driving forces sufficient to dope poorly crystalline regions of the film.

show abstract

“…[ 13 ] Recently, this formalism was expanded for doped semiconducting polymers by incorporating a point charge in proximity of the π‐stacked polymer chains. [ 14,15 ] A notable feature from these simulations is an apparent shift in the position and intensity of the infrared absorption spectrum of the polaron as a function of distance between the counter‐ion and polaron on the polymer.…”

Section: Introductionmentioning

confidence: 98%

Effects of Counter‐Ion Size on Delocalization of Carriers and Stability of Doped Semiconducting Polymers

Thomas

Peterson

Balzer

et al. 2020

Adv Elect Materials

View full text Add to dashboard Cite

Molecular charge transfer dopants either oxidize or reduce the polymeric backbone through accepting or donating an electron. In such cases, the neutralizing counter-ion to the charge carrier on the polymer is the dopant molecule. [1] Protonating the polymer backbone with a Brønsted acid provides a similar effect with the proton donor acting as the counter-ion. [2,3] Electrochemical methods can be used to supply, or remove, electrons if the polymer is supported by a conductive substrate with infiltration of a counter-ion from an electrolyte. [4] These methods effectively tune the electrical conductivity in polymeric semiconductors for emerging applications including bioelectronics [5] and thermoelectrics. [6] For all doping mechanisms, the interactions that exist between a conjugated polymer, a charge carrier, and its corresponding counter-ion are difficult to ascertain. Our lack of understanding stems from a multitude of complications that arise from doping polymers. The morphology of thin films can evolve upon infiltration of dopants, which convolutes the effects of morphology and carrier concentration on the resulting electrical properties. [7] The use of dopants of varying molecular sizes simultaneously changes steric interactions and the energetics of charge transfer, along with the additional possibility of the formation of charge transfer complexes. [8-10] These confounding factors make simple relationships, like how the degree of interaction between the dopant counter-ion and charge carrier impacts the electronic mobility, challenging to determine. A recent formalism to elucidate the importance of interactions between charge carriers and their associated counterions in semiconducting polymers was developed through examining their spectroscopic signatures in the infrared region. The optical properties of polaronic charge carriers in semiconducting polymers are affected by factors such as electronic/vibrational coupling between chains, coulombic interactions, and disorder. [11,12] One model, developed by Spano and coworkers, rationalizes the optical transitions of polaronic carriers in poly(3-hexylthiophene) (P3HT) using a Holstein Hamiltonian modified to incorporate disorder that is present in crystallites of polymers. [13] Both the predicted energies of the optical transitions and their intensities were in good agreement with experimental observations of field-induced charge carriers Since doped polymers require a charge-neutralizing counter-ion to maintain charge neutrality, tailored and high degrees of doping in organic semiconductors requires an understanding of the coupling between ionic and electronic carrier motion. A method of counter-ion exchange is utilized using the polymeric semiconductor poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b] thiophene]-C 14 to deconvolute the effects of ionic/polaronic interactions with the electrical properties of doped semiconducting polymers. In particular, exchanging the counter-ions of the dopant nitrosonium hexafluorophosphate enables investigation into the...

show abstract

Anisotropic Polaron Delocalization in Conjugated Homopolymers and Donor–Acceptor Copolymers

Cited by 52 publications

References 76 publications

Ordered arrangement of F4TCNQ anions in three-dimensionally oriented P3HT thin films

Ordered arrangement of F4TCNQ anions in three-dimensionally oriented P3HT thin films

Tunable Dopants with Intrinsic Counterion Separation Reveal the Effects of Electron Affinity on Dopant Intercalation and Free Carrier Production in Sequentially Doped Conjugated Polymer Films

Effects of Counter‐Ion Size on Delocalization of Carriers and Stability of Doped Semiconducting Polymers

Contact Info

Product

Resources

About