Time-resolved photoluminescence measurement on polythiophene derivative

We measured the time-resolved photoluminescence (PL) on a film of a polythiophene derivative to investigate the formation and relaxation processes of a self-trapped exciton (STE). On the highand low-energy sides of the PL spectrum, we observed an ultrafast decay component emitted during the STE formation. We also found that PL of the derivative originates from two STE states with opposite symmetries. The coexistence of the two components with different lifetimes and different spectra results in a spectral change and biexponential decay. The π conjugated polymer shows such complex PL dynamics because electron-electron and electron-phonon interactions are essential in its relaxation process.