Benzothienobenzothiophene-Based Organic Charge Transfer Complex and Carbon Nanotube Composites for p-Type and n-Type Thermoelectric Materials and Generators

Organic charge transfer complexes (CTCs) or electron donor-acceptor complexes have been intensively studied as organic semiconductors or organic conductors in organic electronics. Herein, the composite of CTCs and single-walled carbon nanotubes (SWCNTs) is studied as both p-type and n-type thermoelectric materials for flexible thermoelectric generators. CTCs are formed by [1]benzothieno[3,2-b][1]benzothiophene (BTBT) derivatives with different side chains as electron donors and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F(4)TCNQ) as electron acceptors. The thermoelectric properties of the composites as well as the effect of side chains in BTBT derivatives are investigated. It is found that the PhBTBT-F(4)TCNQ/SWCNT composite film shows the highest p-type power factor of 244.3 mu W m(-1) K-2; while the C8BTBT-F(4)TCNQ/SWCNT composite film exhibits the highest n-type power factor of 105.1 mu W m(-1) K-2. The thermoelectric module based on five p-n junctions of C8BTBT-F(4)TCNQ/SWCNT exhibits the highest output voltage of 13.1 mV and output power of 340 nW under a 38 K temperature gradient. This device performance is mainly generated from the moderate carrier concentrations and low film defects in the n-type C8BTBT-F(4)TCNQ/SWCNT composite film.

Automated summary

The study focuses on the composite of organic charge transfer complexes (CTCs) and single-walled carbon nanotubes (SWCNTs) as thermoelectric materials for flexible thermoelectric generators, where different side chains of BTBT derivatives and F(4)TCNQ are component of the CTCs. The highest p-type power factor is observed in PhBTBT-F(4)TCNQ/SWCNT composite film, while the highest n-type power factor is found in C8BTBT-F(4)TCNQ/SWCNT composite film.