The nanoscale interpenetrating electron donor–acceptor network in organic bulk heterojunction (BHJ) solar cells results in efficient charge photogeneration but creates complex 3D pathways for charge transport. At present, little is known about the extent to which out‐of‐plane charge flow relies on lateral electrical connectivity. In this work, a procedure, based on conductive atomic force microscopy, is introduced to quantify lateral current spreading during out‐of‐plane charge transport. Using the developed approach, the dependence of lateral spreading on BHJ phase separation, composition, and molecule type (small molecule vs polymer) is studied. In the small‐molecule BHJ, 7,7′‐(4,4‐bis(2‐ethylhexyl)‐4
The crystal structures of the charge‐transfer (CT) cocrystals formed by the π‐electron acceptor 1,3,4,5,7,8‐hexafluoro‐11,11,12,12‐tetracyanonaphtho‐2,6‐quinodimethane (F6TNAP) with the planar π‐electron‐donor molecules triphenylene (TP), benzo[
- NSF-PAR ID:
- 10459801
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Functional Materials
- Volume:
- 29
- Issue:
- 49
- ISSN:
- 1616-301X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract The synthesis and characterization of new semiconducting materials is essential for developing high‐efficiency organic solar cells. Here, the synthesis, physiochemical properties, thin film morphology, and photovoltaic response of ITN‐F4 and ITzN‐F4, the first indacenodithienothiophene nonfullerene acceptors that combine π‐extension and fluorination, are reported. The neat acceptors and bulk‐heterojunction blend films with fluorinated donor polymer poly{[4,8‐bis[5‐(2‐ethylhexyl)‐4‐fluoro‐2‐thienyl]benzo[1,2‐b:4,5‐
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null (Ed.)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
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