The Diffusion of Triplet Excitons in Perylenediimide Derivative Crystals

Perylenediimide derivatives are materials that exhibit singlet fission (SF), capable of absorbing a single photon to generate multiple triplet excitons. This exciton multiplication process holds the potential to surpass the Shockley-Queisser limit. To effectively harness the energy of triplet excitons, they must possess sufficient diffusion capability. However, the diffusion of triplet excitons in perylenediimide derivatives has rarely been studied. In this work, we synthesized perylenediimide derivative crystals (C5) and fabricated composites (C5-Pe-QDs) by incorporating surface-ligand-functionalized quantum dots (Pe-QDs) at varying concentrations. The Pe-QDs act as traps within the C5 crystals, capturing triplet excitons when they diffuse into their capture range. The experimental and computational results indicate that the diffusion coefficient of triplet excitons in C5 crystals is approximately 3.58 × 10⁻⁵ cm² s⁻¹, with a diffusion length of about 50.9 nm. Using Monte Carlo simulations, we estimated the triplet exciton capture probability by Pe-QDs under ideal distribution conditions to be around 79.5%. The above findings indicate that, in the C5-Pe-QDs composites, triplet excitons can efficiently diffuse to the quantum dots, providing a novel and viable pathway for the effective utilization of triplet exciton energy in silicon-based photovoltaic systems.