- School of Chemistry - Research Publications
School of Chemistry - Research Publications
Permanent URI for this collection
2 results
Filters
Reset filtersSettings
Statistics
Citations
Search Results
Now showing
1 - 2 of 2
-
ItemCompetitive Triplet Formation and Recombination in Crystalline Films of Perylenediimide Derivatives: Implications for Singlet FissionMasoomi-Godarzi, S ; Hall, CR ; Zhang, B ; Gregory, MA ; White, JM ; Wong, WWH ; Ghiggino, KP ; Smith, TA ; Jones, DJ (AMER CHEMICAL SOC, 2020-05-28)Developing photostable compounds that undergo quantitative singlet fission (SF) is a key challenge. As SF necessitates electron transfer between neighboring molecules, the SF rate is highly sensitive to intermolecular coupling in the solid state. We investigate SF in thin films for a series of perylenediimide (PDI) molecules. By adding different substituents at the imide positions, the packing of the molecules in the solid state can be changed. The relationship between SF parameters and the stacked geometry in PDI films is investigated, with two-electron direct coupling found to be the main SF mechanism. Time-resolved emission and transient absorption data show that all of the PDI films undergo SF although with different rates and yields varying from 35 to 200%. The results show that PDI1 and 2, which are stacked PDI pairs twisted out of alignment along the highest occupied molecular orbital to lowest unoccupied molecular orbital transition, exhibit faster and more efficient SF up to 200% yield. We demonstrate that both triplet formation and decay rates are highly sensitive to the ordering of the molecules within a film. The results of this study will assist in the design of optimized structures with a fast SF rate and low recombination rate that are required for useful light harvesting applications.
-
ItemFRET-enhanced photoluminescence of perylene diimides by combining molecular aggregation and insulationZhang, B ; Lyskov, I ; Wilson, LJ ; Sabatini, RP ; Manian, A ; Soleimaninejad, H ; White, JM ; Smith, TA ; Lakhwani, G ; Jones, DJ ; Ghiggino, KP ; Russo, SP ; Wong, WWH (Royal Society of Chemistry, 2020-07-14)The photoluminescence quantum yield (ϕPL) of perylene diimide derivatives (PDIs) is often limited by aggregation caused quenching (ACQ) at high concentration or in the neat solid-state. Energy transfer in high dye concentration systems is also a key factor in determining ϕPL as a result of energy funneling to trap sites in the sample. By tuning the substituents, we present two classes of PDIs with aggregation and insulation of the PDI core. By combining these fluorophores in a polymer film, we demonstrate highly emissive samples (85% ϕPL) at high concentration (140 mM or 20% w/w). Experimental and theoretical studies provide insight into why such a combination is necessary to achieve high ϕPL. While insulated fluorophores maintain respectable ϕPL at high concentration, an improved ϕPL can be achieved in the presence of appropriately oriented fluorophore aggregates as emissive traps. The theoretical calculations show that the relative orientation of aggregated monomers can result in energetic separation of localized states from the charge-transfer and bi-excitonic states thereby enabling high ϕPL.