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Title: Charge-transfer biexciton annihilation in a donor–acceptor co-crystal yields high-energy long-lived charge carriers
Organic donor–acceptor (D–A) co-crystals have attracted much interest due to their important optical and electronic properties. Co-crystals having ⋯DADA⋯ π-stacked morphologies are especially interesting because photoexcitation produces a charge-transfer (CT) exciton, D˙ + –A˙ − , between adjacent D–A molecules. Although several studies have reported on the steady-state optical properties of this type of CT exciton, very few have measured the dynamics of its formation and decay in a single D–A co-crystal. We have co-crystallized a peri -xanthenoxanthene ( PXX ) donor with a N , N -bis(3-pentyl)-2,5,8,11-tetraphenylperylene-3,4:9,10-bis(dicarboximide) ( Ph4PDI ) acceptor to give an orthorhombic PXX – Ph4PDI ⋯DADA⋯ π-stacked co-crystal with a CT transition dipole moment that is perpendicular to the transition moments for S n ← S 0 excitation of PXX and Ph4PDI . Using polarized, broadband, femtosecond pump–probe microscopy, we have determined that selective photoexcitation of Ph4PDI in the single co-crystal results in CT exciton formation within the 300 fs instrument response time. At early times (0.3 ≤ t ≤ 500 ps), the CT excitons decay with a t −1/2 dependence, which is attributed to CT biexciton annihilation within the one-dimensional ⋯DADA⋯ π-stacks producing high-energy, long-lived (>8 ns) electron–hole pairs in the crystal. These energetic charge carriers may prove useful in applications ranging from photovoltaics and opto-electronics to photocatalysis.  more » « less
Award ID(s):
2003739
PAR ID:
10229729
Author(s) / Creator(s):
; ; ; ; ; ; ;
Date Published:
Journal Name:
Chemical Science
Volume:
11
Issue:
35
ISSN:
2041-6520
Page Range / eLocation ID:
9532 to 9541
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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