Giant Seebeck Effect of Dibenzo[g,p]chrysene and its Derivatives: Deuteration and Substituent Effects and Relationship with Interlayer Distance

Thermoelectric properties of undoped crystals of dibenzo[g,p]chrysene (DBC), deuterated DBC (DBC‐d16), and 2,10‐dimethyl‐DBC (DBC‐Me2) have been studied to obtain some insights into the relationship between the structural parameters of materials and the giant Seebeck effect. X‐ray crystallography showed one‐dimensional columnar packing with the interlayer distances (d) for DBC‐d16, DBC, and DBC‐Me2 were 3.78 Å, 3.79 Å, and 3.91 Å, respectively. All three compounds formed one‐dimensional carrier transport pathways as suggested by the transfer integral calculations. Their Seebeck coefficients (α) were negative, indicating n‐type behavior. DBC‐d16 exhibited among the highest peak Seebeck coefficient (αmax = −114 mV/K) compared to DBC and DBC‐Me2 (αmax = −31 and −22 mV/K, respectively). The power factors of DBC‐d16 and DBC‐Me2 were higher than that of DBC, due to an increase in Seebeck coefficient and conductivity, respectively. Notably, a positive correlation was found between the peak temperature of the Seebeck coefficient and interlayer distance d, while |αmax| correlated negatively with d. Deuteration significantly enhanced |αmax|, likely due to reduced molecular vibrations, though further investigation should consider the effect of dynamic structural fluctuation due to thermal motion.