Determination of the Polaron Density in Chemically Doped Conjugated Polymers
Doctoral thesis, 2024
devices such as computers, mobile phones, and solar cells. While inorganic semiconductors, such as
silicon, currently dominates the industry, organic semiconductors offer promising alternatives. One of
the most widely studied classes of organic semiconductors is conjugated polymers. Chemical doping is
a critical tool that allows to tune their electrical conductivity through the introduction of positive or
negative charge carriers, i.e. polarons, by the addition of dopants. The ability to adjust the polaron
density is essential, as devices that employ conjugated polymers operate within distinct ranges of
charge-carrier concentration. Therefore, accurately measuring and quantifying the number of polarons
is paramount for both material development and device engineering.
This thesis explores methods for measuring the polaron density in the high doping regime. The results
suggest that optical methods can be used to effectively estimate the polaron density in chemically
doped conjugated polymers. The methodology is then used to demonstrate that chemical doping
significantly effects the mechanical and rheological properties of conjugated polymers. Furthermore,
it is found that the concept of double doping, which involves the transfer of two electrons between
the polymer and the dopant molecule, is a generic concept that extends beyond quinodimethane-type
dopants. The concepts elucidated in this thesis aid the development of an in-depth understanding of
structure-property relationships relevant for doped conjugated polymers. Through addressing
fundamental questions and establishing a foundation for future inquiry, this thesis contributes to the
ongoing advancement of the dynamic field of organic electronics.
organic semiconductors
chemical doping
spectroscopy
molecular dopants polaron density
conjugated polymers
double doping
Author
Emmy Järsvall
Chalmers, Chemistry and Chemical Engineering, Applied Chemistry
Double Doping of a Low-Ionization-Energy Polythiophene with a Molybdenum Dithiolene Complex
Chemistry of Materials,;Vol. 34(2022)p. 5673-5679
Journal article
Delocalization Enhances Conductivity at High Doping Concentrations
Advanced Functional Materials,;Vol. In Press(2022)
Journal article
Tuning of the elastic modulus of a soft polythiophene through molecular doping
Materials Horizons,;Vol. 9(2022)p. 433-443
Journal article
Impact of oxidation-induced ordering on the electrical and mechanical properties of a polythiophene co-processed with bistriflimidic acid
Journal of Materials Chemistry C,;Vol. In Press(2022)
Journal article
Visualisation of individual dopants in a conjugated polymer: sub-nanometre 3D spatial distribution and correlation with electrical properties
Nanoscale,;Vol. In Press(2022)
Journal article
Chemical Doping of Conjugated Polymers with the Strong Oxidant Magic Blue
Advanced Electronic Materials,;Vol. 6(2020)
Journal article
En av de mest undersökta klasserna av organiska halvledare är konjugerade polymerer, som kan liknas vid halvledande plaster med förmåga att leda elektrisk ström tack vare sin kemiska struktur. För att integreras i modern teknik krävs det att dessa material har tillräckligt hög ledningsförmåga, vilket kan uppnås genom kemisk dopning. Via tillsats av dopningsmolekyler kan kemisk dopning justera den elektriska ledningsförmågan hos konjugerade polymerer genom att introducera positiva eller negativa laddningsbärare, så kallade polaroner. Eftersom enheter som använder konjugerade polymerer arbetar inom specifika områden av polaronkoncentration, så är det avgörande att kunna mäta antalet polaroner i materialet för att förstå och optimera enheternas prestanda. Det huvudsakliga syftet med denna doktorsavhandling är att utforska metoder som gör det möjligt att mäta höga polaronkoncentrationer i kemiskt dopade konjugerade polymerer. Av resultaten framgår det att optiska tekniker effektivt kan påvisa polarontätheten i dessa material. Dessutom belyser denna avhandling betydande effekter av kemisk doping på mekaniska och reologiska egenskaper, vilket understryker de mångfacetterade effekterna av kemisk dopning på konjugerade polymerer. Genom att adressera grundläggande frågor och lägga grunden för framtida forskning bidrar denna avhandling till att främja vår förståelse av organisk elektronik.
Roots
Basic sciences
Subject Categories
Materials Chemistry
Areas of Advance
Materials Science
ISBN
978-91-8103-018-1
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5476
Publisher
Chalmers
KC-salen, Kemigården 4
Opponent: Bob Schroeder, University College London, United Kingdom