Ultra-fast intramolecular singlet fission to persistent multiexcitons by molecular design

Singlet fission in a hexacene dimer: energetics dictate dynamics

“…[10][11][12][13][14][15][16][17][18] Dimers serve as model systems to study singlet ssion. They represent the fundamental smallest number of chromophores required for SF and varying the connectivity between the chromophores can lead to insightful structure-property relationships of the constrained excitons, from the generation, [19][20][21][22] separation, [23][24][25][26] and recombination [27][28][29][30] of triplet states, to the elucidation of the bound triplet pair state. [31][32][33][34] It has been established that molecular vibrations play a key role in mediating singlet ssion in both oligoacene molecular crystals (intermolecular singlet ssion, xSF) and in acene intramolecular singlet ssion (iSF) compounds.…”

Fluctuating exchange interactions enable quintet multiexciton formation in singlet fission

“…Whilst the initial and final states of SF are fairly simple and well understood, the dynamic pathways that allow transitions between them are complex [5][6][7] . Recent experimental results have revealed the presence of quintet excitons involved in the SF process [8][9][10] , an observation which has become even more interesting as these higher spin states are observed in more classes of molecular system which undergo SF [11][12][13] . This has raised questions related to the underlying mechanism which generate quintet states, and motivates the work described below.…”

Application of Intramolecular Singlet Fission in Photovoltaics: Control over Multiexciton Generation and Triplet–Triplet Annihilation

“…However, this causes rapid triplet–triplet annihilation, which adversely affects the performance of SF‐based photovoltaics. There are two recent successful studies focusing on separation of multiexciton generation kinetics and triplet decay dynamics . The first, by Pun et al ., employed the concept of an energy cleft .…”

“…There are two recent successful studies focusing on separation of multiexciton generation kinetics and triplet decay dynamics . The first, by Pun et al ., employed the concept of an energy cleft . They designed bipentacene chromophores connected with a tetracene bridge.…”

“…Relatively low performance in the QOT2/AQ model system can be improved by long‐lived charge‐carrier donor states. The other two recent studies show that this could be achieved by delicate structural modifications of SF materials . Further research to couple these promising SF chromophores with appropriate electron acceptors and to fabricate SF‐based photovoltaic cells is worthy.…”