Related Experiment Video
Updated: Jun 27, 2026
06:16
Monitoring the Effects of Illumination on the Structure of Conjugated Polymer Gels Using Neutron Scattering
Published on: December 21, 2017
Electronic structure of disordered conjugated polymers: polythiophenes
Nenad Vukmirović1, Lin-Wang Wang
1Computational Research Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA. NVukmirovic@lbl.gov
The Journal of Physical Chemistry. B
|December 23, 2008
Summary
Disordered semiconducting polymers like P3HT and PT show electronic structure variations. Disorder in P3HT arises from chain conformation, while PT also involves interchain electronic coupling.
Area of Science:
- Materials Science
- Computational Chemistry
- Solid State Physics
Background:
- Semiconducting conjugated polymers are crucial for organic electronics.
- Understanding their electronic structure is key to device performance.
- Disorder significantly impacts charge transport properties.
Purpose of the Study:
- Investigate the origin of electronic disorder in poly(3-hexylthiophene) (P3HT) and polythiophene (PT).
- Determine the degree of carrier localization and the role of chain interactions.
- Elucidate the impact of conformational disorder and interchain coupling on electronic structure.
Main Methods:
- Classical molecular dynamics simulations for atomic structure.
- Charge patching method for electronic structure calculations.
- Analysis of density of states and wave functions.
Main Results:
- Disorder in P3HT electronic structure stems from conformational disorder within chains.
- Polythiophene exhibits additional disorder from interchain electronic coupling.
- Wave functions in P3HT localize on single chains, primarily due to ring torsions.
- PT wave functions are more complex, influenced by interchain coupling.
Conclusions:
- Conformational disorder is the primary source of electronic heterogeneity in alkyl-substituted polythiophenes.
- Interchain coupling significantly affects electronic structure in polythiophene.
- Ring torsions play a dominant role in carrier localization in P3HT.
Related Concept Videos
01:16Structure of Conjugated Dienes
Introduction
Conjugated dienes are compounds characterized by the presence of alternating double and single bonds. In a conjugated system like 1,3-butadiene, the unhybridized 2p orbital on each carbon overlaps continuously, allowing the π electrons to be delocalized across the entire molecule. In contrast, this type of overlap does not occur in cumulated and isolated dienes, such as 2,3-pentadiene and 1,4-pentadiene, respectively. Instead, the π electrons remain localized between the double...
Conjugated dienes are compounds characterized by the presence of alternating double and single bonds. In a conjugated system like 1,3-butadiene, the unhybridized 2p orbital on each carbon overlaps continuously, allowing the π electrons to be delocalized across the entire molecule. In contrast, this type of overlap does not occur in cumulated and isolated dienes, such as 2,3-pentadiene and 1,4-pentadiene, respectively. Instead, the π electrons remain localized between the double...
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
01:21Polymer Classification: Crystallinity
Unlike ionic or small covalent molecules, polymers do not form crystalline solids due to the diffusion limitations of their long-chain structures. However, polymers contain microscopic crystalline domains separated by amorphous domains.
Crystalline domains are the regions where polymer chains are aligned in an orderly manner and held together in proximity by intermolecular forces. For example, chains in the crystalline domains of polyethylene and nylon are bound together by van der Waals...
Crystalline domains are the regions where polymer chains are aligned in an orderly manner and held together in proximity by intermolecular forces. For example, chains in the crystalline domains of polyethylene and nylon are bound together by van der Waals...
01:26Photochemical Electrocyclic Reactions: Stereochemistry
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
01:17Thermal Electrocyclic Reactions: Stereochemistry
The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
01:18Aromatic Hydrocarbon Cations: Structural Overview
Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group with both...
Removing one hydrogen from the intervening CH2 group with both...