High pressure effects in picosecond & C.W. spectroscopies of conjugated polymers

Abstract We have studied polydiacetylene(PDA) and polythiophene films under hydrostatic pressure up to 60 kbar. In PDA-4BCMU, the excitonic recovery time increases from a 1.5 psec exponential decay at atmospheric pressure, to a nonexponential decay over several decades in time at high pressures. In poly (3-hexylthiophene), (P3HT), the absorption and photoluminescence (PL) bands exhibit similar redshifts that saturate near 40 kbar and the thermochromic effect is completely inhibited at high pressures. We suggest that these effects in both PDA and P3HT polymers are due to the inhibition of out-of-plane rotations by the application of pressure.