Organic photovoltaic (OPV) efficiencies continue to rise, raising their prospects for solar energy conversion. However, researchers have long considered how to suppress the loss of free carriers by recombination-poor diffusion and significant Coulombic attraction can cause electrons and holes to encounter each other at interfaces close to where they were photogenerated. Using femtosecond transient spectroscopies, we report the nanosecond grow-in of a large transient Stark effect, caused by nanoscale electric fields of ∼487 kV/cm between photogenerated free carriers in the device active layer. We find that particular morphologies of the active layer lead to an energetic cascade for charge carriers, suppressing pathways to recombination, which is ∼2000 times less than predicted by Langevin theory. This in turn leads to the buildup of electric charge in donor and acceptor domains-away from the interface-resistant to bimolecular recombination. Interestingly, this signal is only experimentally obvious in thick films due to the different scaling of electroabsorption and photoinduced absorption signals in transient absorption spectroscopy. Rather than inhibiting device performance, we show that devices up to 600 nm thick maintain efficiencies of >8% because domains can afford much higher carrier densities. These observations suggest that with particular nanoscale morphologies the bulk heterojunction can go beyond its established role in charge photogeneration and can act as a capacitor, where adjacent free charges are held away from the interface and can be protected from bimolecular recombination.
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http://dx.doi.org/10.1021/jacs.9b12526 | DOI Listing |
Mater Horiz
January 2025
Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Straße 24/25, 14476, Germany.
Two-dimensional transition metal dichalcogenides (2D TMDCs) can be combined with organic semiconductors to form hybrid van der Waals heterostructures. Specially, non-fullerene acceptors (NFAs) stand out due to their excellent absorption and exciton diffusion properties. Here, we couple monolayer tungsten diselenide (ML-WSe) with two well performing NFAs, ITIC, and IT-4F (fluorinated ITIC) to achieve hybrid architectures.
View Article and Find Full Text PDFNano Lett
January 2025
National Key Laboratory of Uranium Resources Exploration-Mining and Nuclear Remote Sensing, East China University of Technology, Nanchang 330013, China.
Efficient sacrificial-agent-free photosynthesis of HO from air and water represents the greenest, lowest-cost, most real-time avenue for HO production but remains a challenging issue. Here, we show a general and effective approach through a structural design on covalent organic frameworks (COFs) with asymmetric dual-function hybrid linkages for boosting the HO photosynthesis of the COFs. Through such design we can equip a COF with not only a catalytic active center but also a special function for isolating the D-A motif, which consequently endows the COF (CI-COF) built on asymmetric dual-function hybrid linkages with a significantly enhanced efficiency in the generation, transmission, and separation of photogenerated carriers, relative to the COF (II-COF and CC-COF) built on symmetric single-function single linkages.
View Article and Find Full Text PDFRSC Chem Biol
January 2025
Department of Chemical and Biological Engineering, University of Wisconsin - Madison Madison Wisconsin 53706 USA
Cyanobacteria are widespread, photosynthetic, gram-negative bacteria that generate numerous bioactive secondary metabolites complex biosynthetic enzymatic machinery. The model cyanobacterium sp. strain PCC 7002, hereafter referred to as PCC 7002, contains a type I polyketide synthase (PKS), termed olefin synthase (OlsWT), that synthesizes 1-nonadecene and 1,14-nonadecadiene: α-olefins that are important for growth at low temperatures.
View Article and Find Full Text PDFACS Appl Mater Interfaces
January 2025
Institute of New Energy Technology, College of Physics & Optoelectronic Engineering, Jinan University, Guangzhou 510632, China.
CsSbBr, as a sort of novel lead-free perovskite single crystal, has the merits of high carrier mobility and a long diffusion length. However, the large-sized and high-crystallized CsSbBr single crystals are not easily obtained. Herein, we apply the vertical Bridgman method to grow centimeter-sized CsSbBr single crystal.
View Article and Find Full Text PDFNat Nanotechnol
January 2025
Key Laboratory of Bio-inspired Materials and Interfacial Science, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, China.
The miniaturization of light-emitting diodes (LEDs) is pivotal in ultrahigh-resolution displays. Metal-halide perovskites promise efficient light emission, long-range carrier transport and scalable manufacturing for bright microscale LED (micro-LED) displays. However, thin-film perovskites with inhomogeneous spatial distribution of light emission and unstable surface under lithography are incompatible with the micro-LED devices.
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