Accelerating Symmetry-Breaking Charge Separation in an Angular versus Linear Perylenediimide Dimer through the
Aniruddha Mazumder1, Kavya Vinod1, Aivin Chemmarappallil Thomas1
1School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, Maruthamala P.O., Vithura, Thiruvananthapuram, Kerala, India 695551.
Abstract:
Achieving faster charge separation in organic systems capable of mimicking the electron transfer events in natural photosynthesis has been an exciting research topic for several decades. Herein, we demonstrate the orientation-dependent acceleration of symmetry-breaking charge separation (SB-CS) in an angular (A-PDI2) versus linear (L-PDI2) perylenediimide dimer. Femtosecond transient absorption measurements reveal ultrafast SB-CS in A-PDI2 (τ = 6.3 ps) with charge separation ∼20 times faster than in L-PDI2 (τ = 127.9 ps). Nanosecond transient absorption measurements establish the negligible population of triplet excited-states in L-PDI2 (ϕ < 1%), whereas a significant triplet excited-state population (ϕ = 35.9%) is quantified in A-PDI2. The theoretically computed Coulombic coupling strength in A-PDI2 (|J| = 14.9 cm-1) and L-PDI2 (|J| = 438.4 cm-1) is rationalized as the crucial factor modulating the SB-CS rates. The current investigation could be beneficial for designing light harvesting materials capable of faster charge separation for efficient optoelectronic devices.
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