Improved thermoelectric performance of organic thin-film elements utilizing a bilayer structure of pentacene and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ)

Abstract

We demonstrate an improved thermoelectric performance of small molecular thin films fabricated by thermal deposition of pentacene as a $p$ -type conduction layer. To enhance the performance, a bilayer structure composed of an intrinsic pentacene layer and an acceptor 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane layer is utilized as the prototype thermoelectric element. With the bilayer structure, the electrical conductivity reaches 0.43 S/cm, exhibiting a positive Seebeck coefficient of about $200\mu \text{V}/\text{K}$ . We thus obtain a high power factor of $2.0\mu \text{W}/{\text{mK}}^2$ with an optimized layer thickness.