Magnetic field dependence of singlet fission in solutions of diphenyl tetracene

Abstract

Magnetic field effects provide a convenient and specific probe of singlet exciton fission within optoelectronic devices. Here, we demonstrate that this tool may also be applied to screen potential fission material candidates in solution. We characterize the phenomenon in diphenyl tetracene (DPT), which shows strong fluorescence modulation and the expected field dependence in its transient decay as a function of concentration. Solution measurements may also be used to test for the presence of an intermediate charge transfer state, but we observe no changes to the field dependence of DPT singlet exciton fission in toluene relative to chloroform.

Singlet and Triplet Exciton Dynamics of Violanthrone

“…It is well established that a pool of statistically populated triplets undergo inhibited triplet-triplet annihilation in magnetic fields, the effect usually being of the order of several percent at fields of 3000 G. [38] By the principle of detailed balance, one would therefore also expect the singlet fission process to produce a pool of statistical triplets to be hindered, and thus potentially enhanced photoluminescence would result. This has been observed in solution [39] and in the solid state. [3,40] However, a magnetic field enhancement of PL requires a quasi-equilibrium between the bright singlet state and the weakly-coupled triplet pair ((T...T )).…”

Efficient Singlet Fission and Triplet-Pair Emission in a Family of Zethrene Diradicaloids

“…a can only be rationalized in terms of these markedly higher triplet energies, measured with the most direct method available, and we suggest that the earlier measurements reflected charged species rather than excitonic triplets, as suggested by ESR measurements 47. Most of the molecules studied exhibit moderately high solution photoluminescence quantum efficiency (PLQE, Table1), indicating that there are concentration-dependent conversion of singlets into two triplet excitons, a hallmark of diffusive SF25,26,48,49 (Supplementary Figures2 and 4−8). The only exception is PF-M, which has an extremely short excited-state lifetime pointing to efficient nonradiative decay (Table1, Supplementary Figure3).…”

Quintet multiexciton dynamics in singlet fission

“…[18] Crucially, it is possible to measure and characterize the quintet character of a triplet pair state 5 (TT) using magnetic resonance techniques. While the magnetic properties of triplet pairs produced by singlet fission have been observed as variations in the optical and transport properties of SF materials in the presence of an applied external field, [18,[36][37][38][39][40][41][42] quintet states have never been directly and unambiguously identified. Once generated, the (TT) state can either dissociate into a lower energy state comprising two isolated triplets (via, for instance, local molecular conformational changes or triplet hopping through a crystal lattice), (Figure 1b,c, Step 3), or decay directly to the ground state, S 0 ( Figure 1b,c Step 4).…”