Triplet Transfer Mediates Triplet Pair Separation during Singlet Fission in 6,13‐Bis(triisopropylsilylethynyl)‐Pentacene

Abstract

Triplet population dynamics of solution cast films of isolated polymorphs of 6,13‐bis(triisopropylsilylethynyl) pentacene (TIPS‐Pn) provide quantitative experimental evidence that triplet excitation energy transfer is the dominant mechanism for correlated triplet pair (CTP) separation during singlet fission. Variations in CTP separation rates are compared for polymorphs of TIPS‐Pn with their triplet diffusion characteristics that are controlled by their crystal structures. Since triplet energy transfer is a spin‐forbidden process requiring direct wavefunction overlap, simple calculations of electron and hole transfer integrals are used to predict how molecular packing arrangements would influence triplet transfer rates. The transfer integrals reveal how differences in the packing arrangements affect electronic interactions between pairs of TIPS‐Pn molecules, which are correlated with the relative rates of CTP separation in the polymorphs. These findings suggest that relatively simple computations in conjunction with measurements of molecular packing structures may be used as screening tools to predict a priori whether new types of singlet fission sensitizers have the potential to undergo fast separation of CTP states to form multiplied triplets.

Striking the right balance of intermolecular coupling for high-efficiency singlet fission

“…We showed above that the average effective mass density decreases in the amorphous nanoparticles in the order TES-Pn > TIPS-Pn > TSBS-Pn. Thus, our observation that triplet pair separation (and by extension, triplet transfer 5 , 18 – 20 , 75 ) is the slowest in the amorphous TSBS-Pn nanoparticles (and vice versa for the amorphous TES-Pn nanoparticles) is wholly consistent with the aforementioned trend in average effective mass density. The second result pertains to the intermolecular structural relaxation step that follows the formation of short-lived nascent triplet pairs ( i.e.…”

Annihilation Versus Excimer Formation by the Triplet Pair in Triplet–Triplet Annihilation Photon Upconversion

“…Typical annihilators like perylene, pyrene, rubrene, and diphenylanthracene have a large flat conjugated structure, thus having the ability to form favorable π–π and electronic interactions stabilizing the triplet pair. 42 , 43 However, the same molecular properties that stabilize the triplet pair also allow dimers to form on the singlet energy surface. 37 , 44 − 46 The excited dimer, consisting of one molecule in its ground state and one in its excited singlet state, is usually referred to as an excimer.…”

Improved Transistor Performance by Modulating Molecular Packing with Donor and Acceptor Moieties

“…The transfer integrals play critical roles in the charge transport process . We calculated the transfer integrals between the adjacent molecules with the energy splitting method . In the 1D slipped molecules of BDOPV and T‐BDOPV, the transfer integrals are 48 and 28 meV respectively (Figure g,h).…”

“…[42] We calculated the transfer integralsb etween the adjacent molecules with the energy splitting method. [43,44] In the 1D slipped molecules of BDOPV and T-BDOPV,t he transfer integralsa re 48 and 28 meV respectively (Figure 3g,h). In the 2D brick-layerc rystal, T-BDOPV-T packed with two kinds of adjacent molecules (Figure 3i), which exhibit the transfer integralso f4 5a nd 29 meV respectively.T he selected-areae lectron diffraction (SAED) was performed to verify the predicted structure and determinet he preferential growth direction (Figure 3j,k,l).…”