Light-induced absorption increase in poly(3,4-ethylenedioxythiophenes) over one-octave optical frequency
Phys. Rev. B 113, 155150 – Published 27 April, 2026
DOI: https://doi.org/10.1103/yhnc-59bb
Abstract
Light-induced absorption change of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) was investigated using femtosecond transient absorption spectroscopy in the visible and near-infrared regions from 0.94 to 2.85 eV. It was found that the photoexcitation of chemical polarons with the near-infrared pulse (photon energy of 1.55 eV) results in a broad absorption increase over these spectral regions at the time origin. This absorption increase was explained by the ultrafast formation of bipolarons in the PEDOTs. The exciton formation with the near-ultraviolet pulse (photon energy of 3.10 eV) induced an absorption increase from 0.95 to 1.48 eV and an absorption decrease from 1.57 to 2.85 eV. This spectral behavior was explained by the sequential bipolaron formation caused by the exciton relaxation via excitation of a neighboring chemical polaron. This study revealed the relaxation processes of excited chemical polarons and excitons in doped conjugated polymers.
