Regensburg 2025 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 15: Poster Session I

CPP 15.43: Poster

Monday, March 17, 2025, 19:00–21:00, P4

Excimer as intermediate in singlet fission process for Polydiketopyrrollopyrole based materials — •Sruthy Asa Rajan, Sergey Bagnich, and Anna Köhler — University of Bayreuth, Bayreuth, Germany

Photovoltaics are essential for renewable energy generation, but the efficiency of conventional solar cells is constrained by the Shockley-Queisser limit, which arises from fundamental and practical losses such as thermalisation loss. Singlet fission (SF), a carrier multiplication process, offers a promising pathway to surpass this efficiency limit. However, a key challenge lies in identifying SF molecules with triplet energy levels that align with the silicon band gap, enabling the efficient formation of correlated triplet pairs, 1(TT) and their subsequent separation into individual triplets.

Polydiketopyrrollopyrole (PDPP) is a molecule with a comparable triplet energy to the silicon bandgap. We investigate the influence of solvent properties on the optical behaviour of N-substituted pyrene-bridged PDPPs. We employ temperature-dependent steady-state and time-resolved photoluminescence studies on N-substituted pyrene-bridged PDPPs in protic polar and aprotic polar solvents to study the evolution of different species. We observe excimer emission at intermediate temperature and 1(TT) emission at lower temperature. This observation supports the notion that excimers are involved in the formation of 1(TT).

Keywords: Singlet fission; Polydiketopyrrollopyrole; Organic solar cells; Excimer