Incorporation of a Boron-Nitrogen Covalent Bond Improves the Charge-Transport and Charge-Transfer Characteristics of Organoboron Small-Molecule Acceptors for Organic Solar Cells

An organoboron small-molecular acceptor (OSMA) M_B←N containing a boron-nitrogen coordination bond (B←N) exhibits good light absorption in organic solar cells (OSCs). In this work, based on M_B←N, OSMA M_B-N, with the incorporation of a boron-nitrogen covalent bond (B-N), was designed. We have systematically investigated the charge-transport properties and interfacial charge-transfer characteristics of M_B-N, along with M_B←N, using the density functional theory (DFT) and the time-dependent density functional theory (TD-DFT). Theoretical calculations show that M_B-N can simultaneously boost the open-circuit voltage (from 0.78 V to 0.85 V) and the short-circuit current due to its high-lying lowest unoccupied molecular orbital and the reduced energy gap. Moreover, its large dipole shortens stacking and greatly enhances electron mobility by up to 5.91 × 10^-3 cm²·V^-1·s^-1. Notably, the excellent interfacial properties of PTB7-Th/M_B-N, owing to more charge transfer states generated through the direct excitation process and the intermolecular electric field mechanism, are expected to improve OSCs performance. Together with the excellent properties of M_B-N, we demonstrate a new OSMA and develop a new organoboron building block with B-N units. The computations also shed light on the structure-property relationships and provide in-depth theoretical guidance for the application of organoboron photovoltaic materials.

A novel 2-(2′-aminophenyl)benzothiazole derivative displays ESIPT and permits selective detection of Zn2+ ions: experimental and theoretical studies

Synthesis of a novel 2-(2′-aminophenyl)benzothiazole based probe (1) and demonstration of excited state intramolecular proton transfer (ESIPT) with a large Stokes shift (∼246 nm) are presented.

Quantum chemical design of carbazole- and pyridoindole-based ambipolar host materials for blue phosphorescent OLEDs

Structure–property relationship of carbazole- and pyridoindole-type host materials for blue PhOLEDs using quantum chemical calculations.

Identifying efficient blue-phosphorescent polymer light-emitting diode host materials based on carbazole derivatives with C/Si-centered substituents using density functional theory

Two series of carbazole derivatives were designed and studied that could potentially be used in polymer light-emitting diodes (PLEDs) as host molecules. These carbazole-based host molecules incorporated substituents with C or Si at their centers at the 3- and 6-positions on the carbazole moiety. Density functional theory calculations were performed to investigate the influence of the substituent on energy and charge transfer, and to predict whether each molecule could act as an effective host material in PLEDs. The results show that, for the series in which the carbazole moiety is linked to the substituent via the central C/Si atom ("cbz-sub series"), triplet-state electron transitions and triplet excitons arise from the carbazole moiety. Members of the cbz-sub series also exhibited higher triplet energies (ET) than the series in which the carbazole moiety is linked to the C/Si-centered substituent via an extra phenyl group ("cbz-ph-sub series"). Moreover, members of the cbz-sub series presented strong molecular orbital interactions and suitable singlet and triplet energy differences (ΔEST). Further investigations showed that, in each series, the presence of an Si atom was more likely to inhibit charge and exciton delocalization, and inserting a methyl or tert-butyl group at the 2- and 7-position, respectively, of the carbazole moiety in the cbz-ph-sub molecules improved their ET values and led to clear intramolecular charge-transfer character. A comparison of the energies of host and guest molecules showed that all of the molecules designed in this work are suitable for use with blue-light guest materials.

Enhanced electron affinity and charge balance property of a bipolar material: highly efficient solution-processed deep blue electrofluorescent and green electrophosphorescent devices

The slight move in the ratio of the donor and acceptor group can slightly affect the optoelectronic property as a whole, and consequently modulate the electron affinity, charge balance property and exciton recombination efficiency.