Triplet excited states are the key products of singlet fission. For organic molecular photovoltaics that incorporate this mechanism, triplet intermediates ultimately generate cations. To characterize and quantify the transient and product species requires a variety of spectroscopic techniques. One that has been under-utilized is resonance Raman spectroscopy, despite inherent advantages of sensitivity and selectivity. We have probed pentacene and bis(triisopropylsilylethynyl, TIPS)-pentacene triplet and cation states with resonance Raman spectroscopy. Experimental spectra are compared with computations to analyze and assign various bands. Frequency shifts of key bands among the triplet, cation, and ground states are compared with expectations based on frontier molecular orbitals of the acenes. These findings may motivate further use of vibronic spectroscopy to probe the singlet fission mechanism.

Triplet excited states and cations of acenes probed with vibronic spectroscopy

ACS Spring Meeting 2021

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