Low Energetic Disorder in Small-Molecule Non-Fullerene Electron Acceptors

The energetic disorder in representative small-molecule non-fullerene electron acceptors (SM-NFAs) exploited in high-efficiency organic solar cells, is quantified via the combination of molecular dynamics simulations and long-range corrected density functional theory calculations. Our results underline that, with respect to the common fullerene acceptor PC71BM, the total energetic disorder related to these SM-NFAs is reduced by as much as one-third. These results help rationalize the origin of the low voltage losses measured in efficient SM-NFA-based organic solar cells

Nature of Highly Efficient Thermally Activated Delayed Fluorescence in Organic Light-Emitting Diode Emitters: Nonadiabatic Effect between Excited States

The discovery and utilization of metal-free organic emitters with thermally activated delayed fluorescence (TADF) is a huge breakthrough toward high-performance and low-cost organic light-emitting diodes. Time-dependent second-order perturbation theory including spin–orbit and nonadiabatic couplings, combined with time-dependent density functional theory, is employed to reveal the nature of highly efficient TADF in pure organic emitters. Our results demonstrate that except energy gaps between the lowest singlet (S₁) and triplet (T₁) excited states the nonadiabatic effect between low-lying excited states should play a key role in the T₁ → S₁ upconversion for TADF emitters, especially donor–acceptor–donor (D–A–D) molecules. We not only clarify the reason why D–A–D molecules with large S₁–T₁ energy gaps show efficient TADF but also explain the experimental observation that D–A–D-type compounds with S₁–T₁ gaps close to those of their D–A-shape counterparts display more efficient T₁ → S₁ upconversion

Theoretical Study on Charge Transport Properties of Intra- and Extra-Ring Substituted Pentacene Derivatives

A series of pentacene derivatives, halogen-substituted and thiophene- and pyridine-substituted, have been studied with a focus on the electronic properties and charge transport properties using density functional theory and classical Marcus charge-transfer theory. The transport properties of holes and electrons have been studied to get insight into the effect of halogenation and heteroatom substitution on transport and injection of charge carriers. The calculation results revealed that fluorination and chlorination can effectively lower the lowest unoccupied molecular orbital (LUMO) level, modulate the hole and electron reorganization energy, improve the stacking mode of the crystal structure, and enhance the ambipolar characteristic. Chlorination gives a better ambipolar characteristic. On the basis of halogen substitution, the substitution of terminal benzene ring of triisopropyl-silylethynyl-pentacene (TIPS-PEN) by a thiophene or pyridine will greatly lower the LUMO level and improve the stacking mode, leading to more suitable ambipolar materials. Hence, both intra- and extra-ring substitution are favorable to enhance the ambipolar transport property of TIPS-PEN

Impact of Organic Spacers on the Carrier Dynamics in 2D Hybrid Lead-Halide Perovskites

We have carried out nonadiabatic molecular dynamics simulations combined with time-dependent density functional theory calculations to compare the properties of the two-dimensional (2D) (BA)2(MA)­Pb2I7 and three-dimensional (3D) MAPbI3 (where MA = methylammonium and BA = butylammonium) materials. We evaluate the different impacts that the 2D-confined spacer layer of butylammonium cations and the 3D-confined methylammonium cations have on the charge carrier dynamics in the two systems. Our results indicate that, while both the MA+ and BA+ cations play important roles in determining the carrier dynamics, the BA+ cations exhibit stronger nonadiabatic couplings with the 2D perovskite framework. The consequence is a faster hot-carrier decay rate in 2D (BA)2(MA)­Pb2I7 than in 3D MAPbI3. Thus, tuning of the functional groups of the organic spacer cations in order to reduce the vibronic couplings between the cations and the Pb–I framework can offer the opportunity to slow down the hot-carrier relaxations and increase the carrier lifetimes in 2D lead-halide perovskites

A Promising Approach to Obtain Excellent <i>n</i>-Type Organic Field-Effect Transistors: Introducing Pyrazine Ring

The effects of the pyrazine ring on the geometrical and electronic structures, molecular stacking motifs, carrier injection, and transport properties as well as electronic band structures for some typical molecules with pyrazines (such as tetracene, pentacene, and π-extended tetrathiafulvalene derivatives) were theoretically investigated by quantum chemical methods. The introduction of pyrazine does not affect the molecular planarity and in the meantime largely decreases the energies of the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals and hence improves their stability in air and ability of electron injection. More important, it is very helpful for prompting the molecular π-stacking. Small electron reorganization energies and large electronic coupling originated from their dense π-stacking give rise to their excellent electron transport properties, which makes them become a class of promising candidates for excellent n-type organic field-effect transistor (OFET) materials. So introducing pyrazine is an effective approach to obtain the excellent n-type OFET materials

Intramolecular Noncovalent Interactions Facilitate Thermally Activated Delayed Fluorescence (TADF)

In the conventional molecular design of thermally activated delayed fluorescence (TADF) organic emitters, simultaneously achieving a fast rate of reverse intersystem crossing (RISC) from the triplet to the singlet manifold and a fast rate of radiative decay is a challenging task. A number of recent experimental data, however, point to TADF emitters with intramolecular π–π interactions as a potential pathway to overcome the issue. Here, we report a comprehensive investigation of TADF emitters with intramolecular π···π or lone-pair···π noncovalent interactions. We uncover the impact of those intramolecular noncovalent interactions on the TADF properties. In particular, we find that folded geometries in TADF molecules can trigger lone-pair···π interactions, introduce a n → π* character of the relevant transitions, enhance the singlet–triplet spin–orbit coupling, and ultimately greatly facilitate the RISC process. This work provides a robust foundation for the molecular design of a novel class of highly efficient TADF emitters in which intramolecular noncovalent interactions play a critical function

DataSheet1_Multiple resonance type thermally activated delayed fluorescence by dibenzo [1,4] azaborine derivatives.docx

We studied the photophysical and electroluminescent (EL) characteristics of a series of azaborine derivatives having a pair of boron and nitrogen aimed at the multi-resonance (MR) effect. The computational study with the STEOM-DLPNO-CCSD method clarified that the combination of a BN ring-fusion and a terminal carbazole enhanced the MR effect and spin-orbit coupling matrix element (SOCME), simultaneously. Also, we clarified that the second triplet excited state (T2) plays an important role in efficient MR-based thermally activated delayed fluorescence (TADF). Furthermore, we obtained a blue–violet OLED with an external EL quantum efficiency (EQE) of 9.1%, implying the presence of a pronounced nonradiative decay path from the lowest triplet excited state (T1).</p

De Novo Designed Self-Assembling Rhodamine Probe for Real-Time, Long-Term and Quantitative Live-Cell Nanoscopy

Super-resolution imaging provides a powerful approach to image dynamic biomolecule events at nanoscale resolution. An ingenious method involving tuning intramolecular spirocyclization in rhodamine offers an appealing strategy to design cell-permeable fluorogenic probes for super-resolution imaging. Nevertheless, precise control of rhodamine spirocyclization presents a significant challenge. Through detailed study of the structure–activity relationship, we identified that multiple key factors control rhodamime spirocyclization. The findings provide opportunities to create fluorogenic probes with tailored properties. On the basis of our findings, we constructed self-assembling rhodamine probes for no-wash live-cell confocal and super-resolution imaging. The designed self-assembling probe Rho-2CF3 specifically labeled its target proteins and displayed high ring-opening ability, fast labeling kinetics (80 folds), which is very difficult to be realized by the existing methods. Using the probe, we achieved high-contrast super-resolution imaging of nuclei and mitochondria with a spatial resolution of up to 42 nm. The probe also showed excellent photostability and proved ideal for real-time and long-term tracking of mitochondrial fission and fusion events with high spatiotemporal resolution. Furthermore, Rho-2CF3 could resolve the ultrastructure of mitochondrial cristae and quantify their morphological changes under drug treatment at nanoscale. Our strategy thus demonstrates its usefulness in designing self-assembling probes for super-resolution imaging

De Novo Designed Self-Assembling Rhodamine Probe for Real-Time, Long-Term and Quantitative Live-Cell Nanoscopy

Super-resolution imaging provides a powerful approach to image dynamic biomolecule events at nanoscale resolution. An ingenious method involving tuning intramolecular spirocyclization in rhodamine offers an appealing strategy to design cell-permeable fluorogenic probes for super-resolution imaging. Nevertheless, precise control of rhodamine spirocyclization presents a significant challenge. Through detailed study of the structure–activity relationship, we identified that multiple key factors control rhodamime spirocyclization. The findings provide opportunities to create fluorogenic probes with tailored properties. On the basis of our findings, we constructed self-assembling rhodamine probes for no-wash live-cell confocal and super-resolution imaging. The designed self-assembling probe Rho-2CF3 specifically labeled its target proteins and displayed high ring-opening ability, fast labeling kinetics (80 folds), which is very difficult to be realized by the existing methods. Using the probe, we achieved high-contrast super-resolution imaging of nuclei and mitochondria with a spatial resolution of up to 42 nm. The probe also showed excellent photostability and proved ideal for real-time and long-term tracking of mitochondrial fission and fusion events with high spatiotemporal resolution. Furthermore, Rho-2CF3 could resolve the ultrastructure of mitochondrial cristae and quantify their morphological changes under drug treatment at nanoscale. Our strategy thus demonstrates its usefulness in designing self-assembling probes for super-resolution imaging

De Novo Designed Self-Assembling Rhodamine Probe for Real-Time, Long-Term and Quantitative Live-Cell Nanoscopy

Super-resolution imaging provides a powerful approach to image dynamic biomolecule events at nanoscale resolution. An ingenious method involving tuning intramolecular spirocyclization in rhodamine offers an appealing strategy to design cell-permeable fluorogenic probes for super-resolution imaging. Nevertheless, precise control of rhodamine spirocyclization presents a significant challenge. Through detailed study of the structure–activity relationship, we identified that multiple key factors control rhodamime spirocyclization. The findings provide opportunities to create fluorogenic probes with tailored properties. On the basis of our findings, we constructed self-assembling rhodamine probes for no-wash live-cell confocal and super-resolution imaging. The designed self-assembling probe Rho-2CF3 specifically labeled its target proteins and displayed high ring-opening ability, fast labeling kinetics (80 folds), which is very difficult to be realized by the existing methods. Using the probe, we achieved high-contrast super-resolution imaging of nuclei and mitochondria with a spatial resolution of up to 42 nm. The probe also showed excellent photostability and proved ideal for real-time and long-term tracking of mitochondrial fission and fusion events with high spatiotemporal resolution. Furthermore, Rho-2CF3 could resolve the ultrastructure of mitochondrial cristae and quantify their morphological changes under drug treatment at nanoscale. Our strategy thus demonstrates its usefulness in designing self-assembling probes for super-resolution imaging