Interplay of Nanostructure and Molecular Doping of Poly(3-hexylthiophene)
Doctoral thesis, 2019
This thesis discusses thermoelectric plastics and in particular the semiconducting polymer poly(3-hexylthiophene) (P3HT). P3HT is a model conjugated polymer that is commercially available and has become an important reference material for the study of optoelectronic processes in organic semiconductors.
At first, I investigated isotropic thin films of P3HT doped with 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). I chose doping from the vapour phase as this allowed me to disentangle the influence of polymer processing and doping. I demonstrate that by improving the degree of solid state order of P3HT it is possible to strongly increase the electrical conductivity, which enhances the thermoelectric power factor from 0.2 to 2.7 μW m-1 K-2.
Secondly, I explored the impact of orientation on the thermoelectric properties of P3HT. I chose to study highly anisotropic thin films of P3HT, aligned using a high temperature rubbing technique. Further, I investigated free-standing bulk tapes that where uniaxially oriented through tensile drawing. Sequential doping from solution with F4TCNQ or a molybdenum dithiolene complex allowed me to preserve the anisotropy of both thin films and stretched tapes. I found that orientation of the polymer allows to further increase the thermoelectric properties in the direction of alignment. As a result, a power factor of 16 μW m-1 K-2 for tensile drawn tapes and ~ 100 μW m-1 K-2 for rubbed thin films is obtained. Furthermore, oriented P3HT tapes show no change in the glass transition temperature of about 20 C upon doping with a molybdenum dithiolene complex, which suggests that tensile drawing can be used to prepare flexible thermoelectric materials.
Thermoelectric plastic
P3HT
semiconducting polymer
Mo(tfd-COCF3)3
F4TCNQ
structure-property relationships
doping
Author
Jonna Hynynen
Chalmers, Chemistry and Chemical Engineering, Applied Chemistry
I denna avhandling undersöker jag den konjugerade polymeren poly(3-hexyltiofen) (P3HT) och hur dess ledningsförmåga kan kontrolleras genom användningen av olika tillsatser och bearbetningsmetoder. Jag visar också hur denna polymer kan, inte bara leda utan också, generera elektricitet genom användning av dess termoelektriska effekt som gör att värme omvandlas till elektrisk energi. I mitt arbete har jag utforskat P3HT på djupet med början i dess nanostruktur, dvs. dess uppbyggnad i skalan miljondels millimeter, vidare har jag provat egenskaperna hos millimeterstora plastfilmer för att avslutningsvis spinna en 50 meter lång elektriskt ledande tråd. Kanske kommer man i framtiden kunna använda liknande trådar till att väva smarta textilier, för att kunna utnyttja en av de vanligaste energikällorna vi har: vår egen kroppsvärme.
Subject Categories
Materials Engineering
Chemical Sciences
Areas of Advance
Energy
Roots
Basic sciences
ISBN
978-91-7905-161-7
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4628
Publisher
Chalmers
KE Kemivägen 4
Opponent: Professor Sabine Ludwigs, University of Stuttgart, Germany