TY - JOUR

T1 - Radical enhancement of molecular thermoelectric efficiency

AU - Sangtarash, S.

AU - Sadeghi, H.

PY - 2020/3/1

Y1 - 2020/3/1

N2 - There is a worldwide race to find materials with high thermoelectric efficiency to convert waste heat to useful energy in consumer electronics and server farms. Here, we propose a radically new method to enhance simultaneously the electrical conductance and thermopower and suppress heat transport through ultra-thin materials formed by single radical molecules. This leads to a significant enhancement of room temperature thermoelectric efficiency. The proposed strategy utilises the formation of transport resonances due to singly occupied spin orbitals in radical molecules. This enhances the electrical conductance by a couple of orders of magnitude in molecular junctions formed by nitroxide radicals compared to the non-radical counterpart. It also increases the Seebeck coefficient to high values of 200 μV K-1. Consequently, the power factor increases by more than two orders of magnitude. In addition, the asymmetry and destructive phonon interference that was induced by the stable organic radical side group significantly decreases the phonon thermal conductance. The enhanced power factor and suppressed thermal conductance in the nitroxide radical lead to the significant enhancement of room temperature ZT to values ca. 0.8. Our result confirms the great potential of stable organic radicals to form ultra-thin film thermoelectric materials with unprecedented thermoelectric efficiency.

AB - There is a worldwide race to find materials with high thermoelectric efficiency to convert waste heat to useful energy in consumer electronics and server farms. Here, we propose a radically new method to enhance simultaneously the electrical conductance and thermopower and suppress heat transport through ultra-thin materials formed by single radical molecules. This leads to a significant enhancement of room temperature thermoelectric efficiency. The proposed strategy utilises the formation of transport resonances due to singly occupied spin orbitals in radical molecules. This enhances the electrical conductance by a couple of orders of magnitude in molecular junctions formed by nitroxide radicals compared to the non-radical counterpart. It also increases the Seebeck coefficient to high values of 200 μV K-1. Consequently, the power factor increases by more than two orders of magnitude. In addition, the asymmetry and destructive phonon interference that was induced by the stable organic radical side group significantly decreases the phonon thermal conductance. The enhanced power factor and suppressed thermal conductance in the nitroxide radical lead to the significant enhancement of room temperature ZT to values ca. 0.8. Our result confirms the great potential of stable organic radicals to form ultra-thin film thermoelectric materials with unprecedented thermoelectric efficiency.

KW - Electric conductance

KW - Electric power factor

KW - Phonons

KW - Thermal conductivity

KW - Thermoelectricity

KW - Ultrathin films

KW - Waste heat

KW - Electrical conductance

KW - Molecular junction

KW - Nitroxide radicals

KW - Orders of magnitude

KW - Stable organic radicals

KW - Thermal conductance

KW - Thermo-Electric materials

KW - Thermoelectric efficiency

KW - Molecules

U2 - 10.1039/c9na00649d

DO - 10.1039/c9na00649d

M3 - Journal article

VL - 2

SP - 1031

EP - 1035

JO - Nanoscale Advances

JF - Nanoscale Advances

SN - 2516-0230

IS - 3

ER -