Solvent-dependent thermoelectric performance of PC$_{70}$BM

The investigation of the solvent-dependent thermoelectric properties of [6,6]-Phenyl-C71 butyric acid methyl ester, commonly known as PC$_{70}$BM, is reported. This work shows how using different solvents leads to obtain different values of thermoelectric power factor and figure of merit for PC$_{70}$BM. Samples were prepared from solutions of PC$_{70}$BM in five different solvents: chlorobenzene (CB), 1,2-dichlorobenzene (DCB), 1,2,4-trichlorobenzene (TCB), chloroform (CF), and toluene (TO), and their thermoelectric properties were determined by measuring electrical conductivity, Seebeck coefficient, and mobility. By using polar solvents with high boiling points, such as TCB, the value of mobility increased by a factor of 23, electrical conductivity improved by a factor of 13, and enhancement in the negative Seebeck coefficient value from -405 to -460 $\mu$V/K was observed.