This study focuses Oil the microstructural modifications Of regioregular poly(3-hexyl-thiophene) (rr-P3HT) in the small active channel of thin-film transistors (TFTs) during Operations Polarized absorption and micro-Raman spectroscopy analyses allow us to probe directly the conformation transitions of rr-P3HT chains parallel or pci pendicular to the channel by means of exciton bandwidth, interchain electronic coupling. and effective conjugation length The results of absorption spectra and a joint experimental-theoretical study of Raman spectra show that an external source-to-dram electric field can align rr-P3HT chains parallel to the channel improving electrical performance after long-term operations, especially charge transport properties In comparison. the applied external gate field induced ail increase ill amorphous fraction of the rr-P3HT films. After the analysis, we propose a chain rearrangement model driven by an external electric field to interpret the change,; of the effective conjugation length of rr-P3HT. rather than thermal annealing Our observations provide it thorough explanation for the previously unknown relationships of structure-electronic properties under the extended operations of polymer TFT devices.