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)

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 V/K. We thus obtain a high power factor of 2.0 mu W/mK(2) with an optimized layer thickness. (C) 2010 American Institute of Physics. [doi:10.1063/1.3456394]