Schematic diagram of experimental setup and Seebeck coefficient measurement. (A) Molecular structures of DPP derivatives studied in this work. (B) Schematic of the experimental setup. Closely packed molecules enhance the Seebeck coefficient due to stronger intermolecular coupling. (C) Typical measured individual thermovoltage traces and histograms for single F-DPP molecule with 1 mmol/L immersion concentration at a series of ΔT (0, 5, 10, and 15 K). (D) Histograms of single F-DPP molecule thermoelectric voltage measurements with different immersion concentrations (0.01, 0.1, 1 mmol/L). Gaussian fits were plotted in a black dash curve. The horizontal black dash line indicates the baseline of thermoelectric voltage at ΔV_th=0. The Seebeck coefficients were obtained from the thermovoltage as a function of ΔT. Solid lines are linear fitting.