Fab-peptide complexes formed between a 15 residue peptide derived from the HIV-1 gp120 V3 loop and two of its cognate monoclonal antibodies, 5023A and 5025A, were studied using isotope-edited solution nuclear magnetic resonance (NMR) techniques. Since these antibodies neutralize HIV-1 virus with different strain specificities, this study was conducted to better understand the nature of these differences. The amide proton and nitrogen NMR resonances of specific residues were used to monitor the backbone of this peptide in these complexes. Three central residues of this peptide ('RAF') were found to be strongly affected by binding to both antibodies. Several other peptide residues were affected by binding to antibody 5023A but not 5025A. The antibody epitopes mapped by NMR are similar to those obtained previously via PEPSCAN at higher pH. One main difference between the PEPSCAN and NMR determined epitopes for 5023A involved two glycine residues of the peptide. By NMR, one of these glycines was more dramatically affected by antibody binding than predicted by PEPSCAN, while the other was much less so.
Despite the simplified fabrication process and desirable microstructural stability, the limited charge transport properties of block copolymers and double‐cable conjugated polymers hinder the overall performance of single‐component photovoltaic devices. Based on the key distinction in the donor (D)–acceptor (A) bonding patterns between single‐component and bulk heterojunction (BHJ) devices, rationalizing the difference between the transport mechanisms is crucial to understanding the structure–property correlation. Herein, the barrier formed between the D–A covalent bond that hinders electron transport in a series of single‐component photovoltaic devices is investigated. The electron transport in block copolymer‐based devices is strongly dependent on the electric field. However, these devices demonstrate exceptional advantages with respect to the charge transport properties, involving high stability to compositional variations, improved film uniformity, and device reproducibility. This work not only illustrates the specific charge transport behavior in block copolymer‐based devices but also clarifies the enormous commercial viability of large‐area single‐component organic solar cells (SCOSCs).
By employing a femtosecond electric pump pulse, we theoretically investigate the re-excitation dynamics of a “cold” charge transfer (CCT) state at organic donor/acceptor (D/A) interfaces. It is demonstrated that a relaxed CCT state can be pushed to different “hot” CT (HCT) states via experiencing electron (HCT1 state) and/or hole (HCT2 state) higher-energy transitions, where the transition modes and probabilities are primarily determined by the pulse energy. Without the assistance of a charge driving field, both the two HCT states relax to the initial CCT state through different internal conversion processes, whose dynamics are clearly clarified in this work. However, after a driving field is applied, we find that both of the HCT states can be dissociated into free charges before their relaxations. In particular, the HCT2 state is very easily dissociated compared to the HCT1 state, as well as the CCT state, due to the more delocalized hole charge distribution along the donor. In addition, by enhancing the pulse intensity, we can further improve the hole delocalization along the donor so that the pulsed HCT2 state is more favorable to be dissociated. This work underlines the importance of charge delocalization for the interfacial charge dynamics, including both the internal conversion and charge separation, mediated by different intermediate HCT states in organic solar cells.
Ternary bulk heterojunction (BHJ) organic solar cells have energy offsets between multiple donors and acceptors. In such bi-continuous percolating films, electron carriers mainly transport in acceptor materials, and hole carriers typically transport in donor materials. Changing the third component of additional donors or acceptors is a common method to fine-tune the transport properties in ternary BHJs. Experimentally, although there are some empirical guidelines for the mobility evaluation, a clear charge transporting model has still not been fully established in multi-component BHJ films. Herein, we observed a general regularity about charge transport that the charge carriers have higher possibilities to transport in polymeric materials even if only low dosage (<10% in weight) polymeric materials are introduced for both the hole and electron cases. From the extended Su–Schrieffer–Heeger model, a polymer “bridge” assisted charge transport mode in small molecules is proposed after the energy offset exceeds the threshold (ΔEe > 0.15 eV). This work provides a perspective for fine tuning the charge transport property in high-performance ternary organic solar cells.
As electron acceptor materials, organic small molecules with intra-molecular push-pull electronic structure have been widely used in high-efficient organic solar cells (OSCs), usually referred to as non-fullerene acceptor (NFA) molecules....
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