TD-DFT investigation on the low-lying excited states of spiro-bithiophene

In BT intersystem crossing between the S1 singlet state and a triplet (T2) state is expected to be very efficient and in SCPDT is much lower, that explained quantum efficiencies of SCPDT are much higher. Furthermore, in view of their same s-t split energy 0.12 eV, SCPDT and CPDT that is explained that quantum efficiencies corresponding to the isolated branches are preserved.