Stochastic threshold devices using a trap-filling transition (TFT) coupled with molecular dynamics in poly(3-alkylthiophene)s were fabricated as potential key devices for noise-driven bioinspired sensors and information processors. This article deals with variable-temperature direct current conductivity and alternating current impedance measurements for vertical-type device elements of Au/regioregular poly(3-decylthiophene) ((RR−P3DT) , which show multiple conducting states and quasi-stochastic transitions between these states. Noise measurements indicate the -type (if ) and -type (if ) power spectral densities, where and are an applied voltage and the voltage for TFT, respectively. The noise generation is due to the TFT associated with twist dynamics of -conjugated polymers near the order-disorder phase transition (ODT). At 298 K, the quasi-stochastic behavior is more noticeable for RR-P3DT than poly(3-hexylthiophene). The quasi-stochastic property is employed to a stochastic one-directional signal transmitting device using optical-electric conversion. The dynamics of ODT for powder samples were also investigated by differential scanning calorimetry measurements and high-resolution solid-state nuclear magnetic resonance spectroscopy, and the correlation of the molecular structure and dynamics with electric properties was discussed.