Thermal transport in organic semiconducting polymers

Abstract

We report on the thermal conductivities of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate), [6,6]-phenyl C 61-butyric acid methyl ester (PCBM), poly(3-hexylthiophene-2,5-diyl) (P3HT), and P3HT:PCBM blend thin films as measured by time domain thermoreflectance. Thermal conductivities vary from 0:031 6 0:005 to 0:227 6 0:014 W m À1 K À1 near room temperature and exhibit minimal temperature dependence across the range from 319 to 396 K. Thermal conductivities of blend films follow a rule of mixtures, and no percolation threshold is found. Thermal annealing of blend films has a variable effect on thermal conductivity. Finally, the thermal conductivities of P3HT films do not vary with changes in film thickness from 77 to 200 nm. V

Thermal Conductance across Phosphonic Acid Molecules and Interfaces: Ballistic versus Diffusive Vibrational Transport in Molecular Monolayers

“…This is remarkably similar to a number of common polymers measured in the range of 0.1-0.25 W m -1 K -1 . 29,[87][88][89] The sheer mass and number of atoms comprising of the F21PA molecule, as it becomes large enough to accommodate internal scattering, may account for this similarity between the effective thermal conductivity of the molecule and larger polymer species. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Figure 6.…”

“…[20][21][22] Where these structural modifications to the interfaces often rely on some disorder driven by the atomic arrangement, several recent measurements have confirmed an additional, if 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 4 not more effective, avenue to tune the thermal boundary conductance between two solids driven by the chemical bond at the interface. [23][24][25][26][27] With the availability of a wide array of molecules and functional groups, new materials and composite interfaces that utilize interfacial chemistries and bonding have provided a pathway to alter thermal transport at the molecular level, including: functionalized fullerene derivatives that set new extremes to the lowest thermal conductivity for a fully dense solid, [28][29][30] organic and/or inorganic crystalline multilayers with glass like thermal conductivities, [31][32] and functionalized nanocrystalline arrays with nanoparticle-size-tunable thermal transport. [33][34] These aforementioned examples highlight the potential for the use of molecular interfaces to pave a new path forward for tailoring thermal transport in nanosystems.…”

Nanostructured thermosets containing π-conjugated polymer nanophases: Morphology, dielectric and thermal conductive properties

“…It is proposed that the continuous P3HT nanophases such as cylindrical, lamellar and gyroid microdomains will further contribute the improvement of thermal conductance owing to their continuity. Cola et al [42] have shown that pure polythiophene nanofibers can have a thermal conductivity up to ~ 4.4W/mK, which was more than 20 times higher than the bulk polymer value while the polymer still remained amorphous [60,61]. In this case, PCL-b-P3HT-b-PCL triblock copolymer was synthesized via sequential polymerization Epoxy thermosets containing P3HT nanophases were prepared with the copolymer The thermosets displayed enhanced dielectric constant and thermal conductivity…”

Solution-Processable Molecular and Polymer Semiconductors for Thermoelectrics

“…The cross-plane thermal conductivity of thin films of PEDOT:PSS, the current best thermoelectric material, has been reported to be ∼0.25 Wm −1 K −1 by TDTR. 96 Estimates of the anisotropy have been made showing relatively small differences for PEDOT:Tos and PEDOT:PSS even at high electrical conductivity (σ ∼ 1,000 Scm −1 ), e.g., cross-plane values of 0.33 Wm −1 K −1 and in-plane values of 0.37 Wm −1 K −1 . 99,100 However, a systematic study of the thermal conductivity as a function of processing methods and electrical conductivity is still lacking.…”