has been used in commerce.[2] However, inorganic mate rials are expensive, toxic, and require a rather complicated manufacturing process.In general, the thermoelectric efficiency of thermoelec tric materials is represented by the dimensionless figure of merit ZT in Equation 1:where S is the Seebeck coefficient, σ and κ are the elec trical and thermal conductivities, respectively, and T is the absolute temperature. Using current technology, precise data for the thermal conductivity of conjugated polymer films is difficult to obtain. We therefore use the thermoelectric power factor (PF; Equation 2) as an alterna tive parameter to examine the performance of conjugated polymers, where S is the Seebeck coefficient and σ is the electrical conductivity. Various studies showing that the charge transport properties and the electrical conduc tivity in conjugated polymers are influenced by the mole cular structural parameters have already been reported. The molecular structures of conjugated polymers play a Three conjugated polymers with alkyl chains of different lengths are designed and syn thesized, and their structure-property relationship as organic thermoelectric materials is systematically elucidated. All three polymers show similar photophysical properties, thermal properties, and mechanical properties; however, their thermoelectric performance is influ enced by the length of their side chains. The length of the alkyl chain significantly influences the electrical conductivity of the conjugated polymers, and polymers with a short alkyl chain exhibit better conduc tivity than those with a long alkyl chain. The length of the alkyl chain has little effect on the Seebeck coefficient. Only a slight increase in the Seebeck coefficient is observed with the increasing length of the alkyl chain. The purpose of this study is to provide comprehensive insight into finetuning the ther moelectric properties of conjugated polymers as a function of sidechain engineering, thereby providing a novel perspec tive into the design of highperformance thermoelectric con jugated polymers.
