Short-Range Coulomb Interaction Is a Key to Switch the Utilization of Higher Triplet Excitons in Multiresonance Thermally Activated Delayed Fluorescence Doped Film.

Multiresonance thermally activated delayed fluorescence (MR-TADF) materials have attracted widespread attention due to ultrahigh definition display standards. However, many MR-TADF materials lack TADF properties in both the solution and solid states. Interestingly, the TADF characteristics appear once these MR-TADF compounds are doped in a suitable host film, but the precise mechanism involved in the host-guest interaction remains uncertain.

The Role of Terminal Fluorination on Energy Inversion in Organic Solar Cells.

Suppressing non-radiative energy loss (ΔE) mediated by the triplet charge transfer state is crucial for high-performance organic solar cells (OSCs). Here, we decode the energy inversion through multi-scale theoretical simulations, which inhibit the formation of non-emissive triplet (T) state. However, it is mystified by the system dependence.

A hybridization-induced charge-transfer state energy arrangement reduces nonradiative energy loss in organic solar cells.

Here, we explain why the Energy Gap Law and the energy inversion related to the charge-transfer state have opposite effects on the trend of nonradiative energy loss of organic solar cells. The root is the existing condition of energy inversion. There is indeed a certain probability of energy inversion, but it will eventually be implicit or explicit as determined by the hybridization, which depends on the electron-withdrawing unit of the donor, giving rise to different stacking sites.

Cause Analysis and Preventive Measures for Sand Production in Gas Wells of Sulige Gas Field.

Sand production from gas wells has a significant impact on the production of gas wells. This review aims to reveal the reasons for fracturing sand backflow in Sulige Gas Field gas wells and provide targeted preventive measures to prevent fracturing sand backflow. The critical parameters of sand production in gas wells were calculated through theoretical models, and the reasons and mechanisms of fracturing sand backflow in Sulige gas wells were analyzed from three major aspects: production factors, reservoir factors, and process factors.

Energy differences as descriptors for the correlation between and in nonfullerene organic photovoltaics.

ITIC-series nonfullerene organic photovoltaics (NF OPVs) have realized the simultaneous increases of the short-circuit current density () and open-circuit voltage (), called the positive correlation between and , which could improve the power conversion efficiency (PCE). However, it is complicated to predict the formation of positive correlation in devices through simple calculations of single molecules due to their dimensional differences. Here, a series of symmetrical NF acceptors blended with the PBDB-T donor were chosen to establish an association framework between the molecular modification strategy and positive correlation.

Design of single-porphyrin donors toward high open-circuit voltage for organic solar cells via an energy level gradient-distribution screening strategy of fragments: a theoretical study.

Open-circuit voltage (V) is a key factor for improving the power conversion efficiency (PCE) of bulk heterojunction (BHJ) organic solar cells (OSCs). At present, increasing attention has been devoted towards modifying π bridges in single-porphyrin small molecule donors with an A-π-D-π-A configuration to reduce the highest occupied molecular orbital (HOMO) levels and improve the V of devices. However, how to screen the π bridges is a key issue.

Theoretical characterization on photoelectric properties of benzothiadiazole- and fluorene-based small molecule acceptor materials for the organic photovoltaics.

The upper efficiency of heterojunction organic photovoltaics depends on the increased open-circuit voltage (V ) and short-circuit current (J ). So, a higher lowest unoccupied molecular orbital (LUMO) level is necessary for organic acceptor material to possess higher V and more photons absorbsorption in the solar spectrum is needed for larger J . In this article, we theoretically designed some small molecule acceptors (2∼5) based on fluorene (F), benzothiadiazole, and cyano group (CN) referring to the reported acceptor material 2-[{7-(9,9-di-n-propyl-9H-fluoren-2-yl)benzo[c][1,2,5]thiadiazol-4-yl}methylene]malononitrile (1), the crucial parameters affecting photoelectrical properties of compounds 2∼5 were evaluated by the density functional theory (DFT) and time dependent density functional theory (TDDFT) methods.