Mechanism of singlet fission and triplet-pair separation
In plain words
In some organic crystals one absorbed photon can create two energy packets called triplets, which could raise solar-cell efficiency. How the two triplets form and then separate into independent ones is not fully understood.
Precise statement
For acene crystals (tetracene, pentacene) and covalent dimers, determine whether singlet fission proceeds through real charge-transfer intermediates or a coherent superexchange pathway, and identify the rate and mechanism of conversion of the spin-entangled pair 1(TT) into independent triplets (spin mixing to 5(TT) and 3(TT), spatial separation). An answer is an ab initio rate model reproducing measured fission times (about 80 fs in pentacene) and triplet yields.
What would settle it
Nonadiabatic quantum dynamics with ab initio couplings compared with time-resolved spectroscopy and spin-resolved EPR of triplet pairs.