Singlet Fission in Combinatorial Diketopyrrolopyrrole–Rylene Supramolecular Films

Abstract

Two diketopyrrolopyrroles (DPPs) and three rylenes (NDI, dPyr PDI, and dEO PDI) were combined to form six hierarchical superstructures that assemble as a result of orthogonal H-bonding and π•••π stacking. The individual components and the DPP−NDI as well as DPP−PDI pairs were cast into films, and their superstructures were interrogated by electron microscopy and advanced spectroscopy. All six superstructures feature different geometries, causing subtle changes in the solid-state packing of the DPPs. Changes in inter-DPP stacking that are scaffolded by the adjacent rylenes have a subtle impact on both the excited-state dynamics and on activating new pathways such as singlet fission (SF). Our studies demonstrate the unique benefits of combinatorial supramolecular assembly in exploring the impact of structure on advanced light management in the form of SF to afford triplet quantum yields, which are as high as 65% for a correlated pair of triplets and 15% for an uncorrelated pair of triplets.

Understanding the Bound Triplet-Pair State in Singlet Fission

“…Spin states cannot always be inferred from optical spectroscopy alone, and such assumptions can lead to confusion in the literature. 69,70 Photoluminescence measurements can also be used to provide powerful insights into the nature of m (T 1 T 1 ). For example, photoluminescence spectroscopy can yield information about m (T 1 T 1 ) in cases where singlet and m (T 1 T 1 ) exist in equilibrium.…”

3D Electron Diffraction Structure Determination of Terrylene, a Promising Candidate for Intermolecular Singlet Fission

“…In particular, terrylene is a very capable fluorophore, suitable for single molecule spectroscopy [40,41] . Recently, there has been increasing interest in oligorylenes as singlet fission (SF) chromophores [42–48] . SF is the conversion of one photo‐generated singlet exciton into two triplet excitons, [49–53] which may significantly enhance the efficiency of solar cells by harvesting two charge carriers from one high‐energy photon, whose excess energy would otherwise be lost to heat [54] .…”

“…[ 40 , 41 ] Recently, there has been increasing interest in oligorylenes as singlet fission (SF) chromophores. [ 42 , 43 , 44 , 45 , 46 , 47 , 48 ] SF is the conversion of one photo‐generated singlet exciton into two triplet excitons,[ 49 , 50 , 51 , 52 , 53 ] which may significantly enhance the efficiency of solar cells by harvesting two charge carriers from one high‐energy photon, whose excess energy would otherwise be lost to heat. [54] It has been suggested that terrylene may undergo SF, based on time‐dependent density functional theory (TDDFT) calculations of an isolated molecule.…”

Recent Progress in Hydrogen-Bonded π-Conjugated Systems Displaying J-Type Aggregates

“…By making combinations of complementary H-bonded DPPs and PBIs/NDIs, the authors observed differences in the molecular packing of the aggregates and could identify the best combination to achieve triplet quantum yields as high as 65% for a correlated pair of triplets and 15% for uncorrelated pair of triplets. 88…”