Lactone Maximization in Rigid Electron-Deficient Semiconducting Polymers Enabling High n-type Organic Thermoelectric Performance
Maryam Alsufyani a, Marc-Antoine Stoeckel b, Xingxing Chen e, Karl Thorely c, Yuttapoom Puttisong f, Xudong Ji d, Bryan Paulsen d, Jonathan Rivnay d, Simone Fabiano b, Iain McCulloch a
a Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Oxford, OX1 3TA
b Laboratory of Organic Electronics, Department of Science and Technology, Linköping University, Norrköping, Sweden
c Department of Chemistry, University of Kentucky, 125 Chemistry/Physics Building, Lexington
d Department of Biomedical Engineering, Northwestern University, 2145 Sheridan Road, Evanston, United States
e Solar center, Physical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
f Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden
Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe Fall Meeting 2021 (NFM21)
#ThermoElect21. New concepts in organic/hybrid thermoelectrics
Online, Spain, 2021 October 18th - 22nd
Organizers: L. Jan Anton Koster and Derya Baran
Contributed talk, Maryam Alsufyani, presentation 072
Publication date: 23rd September 2021

Three lactone-based rigid semiconducting polymers were deliberately designed to tackle one the major limitations in the development of n-type organic thermoelectrics, such as electrical conductivity and air stability. Here, we show that phenyl core maximization along the backbone can play a major role in optimizing the thermoelectric performance. Especially when combined with the rigid locked conformation imposed by aldol condensation. Experimental and theoretical investigations demonstrated that increasing the phenyl acene content from 0% phenyl (P-0), to 50% (P-50), and 75% (P-75) resulted in progressively i) larger electron affinities up to -4.37 eV due to the increased density of electron withdrawing groups, thereby suggesting a more favorable doping process when employing (N-DMBI) as the dopant. ii) Larger polaron delocalization due to the more planarized conformation, which ultimately led to lower hopping energy barrier. As a consequence, the electrical conductivity increased by three orders of magnitude to achieve values of up to 12 S/cm, which is one the scarcely reported n-type polymers with electrical conductivities over 10 S/cm. Thereby, enabling power factors of 13.2 μWm−1 K−2 , and is among the highest reported in literature for n-type polymers. Importantly, the electrical conductivity of the doped P-75 maintained a high value of 1.2 S/cm after 18 days of exposure to air.  These findings further highlight the benefits of phenyl core maximization to the electronic performance of the materials and suggest this approach as an effective design strategy to optimize the thermoelectric performance, thus also presenting new insights into material design guidelines for the future development of air stable n-type organic thermoelectrics.

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