Fig. 7

Dynamics of the triplet and quintet states. a Tr-EPR of the 10% pentacene in p-terphenyl 1 μm film. The innermost peaks from the centre-field belong to strongly coupled triplets from parallel dimers, ⁵(TT)_||, with the next pair of peaks originating from strongly coupled triplets with a herringbone geometry, ⁵(TT)_//. The penultimate and strongest pair of peaks belong to dissociated parallel triplets and isolated ISC crossing triplets, (T). The outermost peaks are the dissociated triplets from the herringbone quintet. Timescales for the formation and dissociation of spin species are labelled 1–4 on the right-hand side. b Schematic of the triplet and quintet kinetics: (i) formation of ⁵(TT)_||, (ii) formation of ISC (T) and of the ⁵(TT)_/\, (iii) dissociation of the quintets into triplets, (iv) equilibrium state between \(({\mathrm{TT}})_{/\backslash } \rightleftharpoons {\mathrm{T}} + {\mathrm{T}}\), forming a trap-state, whilst (TT)_||→T+T forms long-lived triplets. c, d Show the experimental (circles) and modelled (line) time traces of the parallel and herringbone geometries, respectively. Experimental traces in emission have been inverted for clarity