Chin-Kuen Tai

Electronic and photophysical properties of the bend D–T–A–T–D derivatives for small-molecule organic photovoltaic (SM-OPV) solar cells: a DFT and TD-DFT investigation

A series of D–T–A–T–D derivatives (D, electron-donating moiety; T, π-conjugated linker; A, electron-acceptor moiety) with seven electron donor moieties and various electron abilities are designed to investigate the influence of the donor on photophysical properties for small-molecule organic photovoltaic solar cells. The 4,8-dimethoxybenzodithiophene (D1), triphenyldsramine (D2), 4-methoxy-N-(4-methoxyphenyl)-N-phenylaniline (D3), 9,9-dimethyl-9H-fluorene (D4), 9-methyl-9H-carbazole (D5), 4-methyl-4H-dithieno-pyrrole (D6), and 4,4-dimethyl-4H-cyclopenta-dithiophene (D7) are adopted as the electron donor moiety. The BDTC (buta-1,3-diene-1,1,4,4-tetracarbonitrile) is used for the A moiety, and the thiophene (T) is used for the π-conjugated linker. The optimized structure of D–T–A–T–D derivatives exhibits the bend molecular conformation due to the steric effect within the A moiety. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies of these derivatives are dependent on the electron donating ability of D, which influences the open-circuit voltage and driving force. Reorganization energy suggests that these derivatives are good hole-transporting type materials. Projected density of state analysis demonstrates that in the HOMO, the electron density distribution is delocalized on the terminal D and T moieties, while in the LUMO, the electron density distribution is localized mainly on the A moiety. The maximum absorption peak, which has relatively high light harvesting efficiency, is due to the π to π* transition and can be tuned by the electron-donating ability and the resonance energy of the D moiety. The bend D6–T–A–T–D6/D7–T–A–T–D7 derivatives with D moiety of 4-methyl-4H-dithieno-pyrrole (D6) and 4,4-dimethyl-4H-cyclopenta-dithiophene (D7) are good candidates as electron donor materials for SM-OPV.

Synthesis and stability study of isocyano aryl boronate esters and their synthetic applications

A facile synthesis of isocyano arylboronate esters is reported. Although tri-coordinate boron functional groups are commonly recognized as vulnerable to nucleophilic attack, the newly reported tri-coordinate isocyano arylboronate esters were found to be stable, albeit owing to the presence of an isocyano group. Theoretical calculations, using the DFT/B3LYP/6-31G(d,p) method, revealed that the electron delocalization between the aryl group and the boron atom might contribute to this stability. UV-vis spectroscopic investigations on 2-(4-isocyanophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2a) were in agreement with the theoretical studies, showing a red-shifted absorption compared with that of phenylisonitrile. The reported strategy allows boronate ester substrates to survive throughout two-step operations. Two of the compounds synthesized were successfully exploited in Ugi and Passerini multicomponent reactions to afford corresponding products. In addition, two boron-containing tetrazoles were also prepared under environmentally benign conditions. These results demonstrated that functionalized isocyanides are stable and can be used as strategically as synthetic building blocks.

Theoretical study of 5,10-diphenylindeno[2,1-a]indene (DPI) dyes for dye sensitized solar cells (DSSC)

Six D-DPI-A (D-π-A) dyes combining various arylamine electron donors (diphenylamine and triphenylamine moieties) with a fixed π-linker (DPI) and a fixed electron acceptor (cyanoacrylic acid) were designed to determine their electronic, photophysical and photovoltaic properties. It was found that electron-donating ability correlates positively with the energy of the highest occupied molecular orbital (EHOMO) of the electron donor moiety. Optimized structures and electronic properties (highest occupied molecular orbital energy (EHOMO), lowest unoccupied molecular orbital (ELUMO), and energy difference (Eg) between HOMO and LUMO) were calculated by the density functional theory (DFT/B3LYP/6-31G(d)) method. Photovoltaic properties [electron injection driving force (ΔGinj)] and photophysical properties [oscillator strengths (f), selected absorption wavelengths (

DFT and TD-DFT investigations of metal-free dye sensitizers for solar cells: Effects of electron donors and π-conjugated linker

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Conformational analysis of a seven-membered ring azasugar, (3R,4R,6S)-trihydroxyazepane: Comparison of GIAO calculation and experimental NMR spectra on 13C chemical shifts

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Effects of substituent and solvent on the structure and spectral properties of maleimide derivatives

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