Using Preformed Meisenheimer Complexes as Dopants for n-Type Organic Thermoelectrics with High Seebeck Coefficients and Power Factors

A pre-formed Meisenheimer complex of a naphthalenediimide (NDI) with tetrabutylammonium fluoride (TBAF) is obtained in a simple way by mixing dibrominated 4,9-dibromo-2,7-bis(2-octyldodecyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone and TBAF in solution and used as a dopant for n-type organic thermoelectrics. Two n-type polymers PNDIClTVT and PBDOPVTT are synthesized, n-doped, and characterized as conductive and thermoelectric materials. PNDIClTVT doped with NDI-TBAF presents a high sigma value of 0.20 S cm(-1), a Seebeck coefficient (S) of -1854 mu V K-1, and a power factor (PF) of 67 mu W m(-1) K-2, among the highest reported PF in solution-processed conjugated n-type polymer thermoelectrics. Using 4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)phenyl)dimethylamine and NDI-TBAF as co-dopants, PNDIClTVT has a PF > 35 mu W m(-1) K-2; while for PBDOPVTT sigma = 0.75 S cm(-1) and PF = 58 mu W m(-1) K-2. In this study it is found that an ionic adduct together with a neutral dopant improves the performance of n-type organic thermoelectrics leading to an enhanced power factor, and more generally, the role of such an adduct in polymer doping is also elucidated.

Automated summary

A pre-formed Meisenheimer complex acts as a dopant for n-type organic thermoelectrics, improving their conductivity and thermoelectric properties. The study also demonstrates that the combined effect of an ionic adduct and a neutral dopant can enhance the power factor of the materials.