Fig. 1

Molecular structures and Jablonski diagram with timescale. a Molecular structure of pentacene with corresponding ZFS axes. b Molecular structure of p-terphenyl. c As a result of photoexcitation, pentacene generates triplets via two distinct mechanisms. Coupled pentacene molecules undergo fast (fs–ps) SF leading to two strongly coupled ¹(TT) states which can then populate the quintet state (teal). These can recombine or ultimately dissociate into free triplets. Alternatively, individual pentacene molecules can transition to triplet states via ISC (orange), which is energetically less favourable due the required spin-flip and therefore occurs on slower timescales (ns)