A series of tetrafluorine‐substituted small molecules with a D1‐A‐D2‐A‐D1 linear framework based on indacenodithiophene and difluorobenzothiadiazole is designed and synthesized for application as donor materials in solution‐processed small‐molecule organic solar cells. The impacts of thiophene π‐bridge and multiple fluorinated modules on the photophysical properties, the energy levels of the highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO), charge carrier mobility, the morphologies of blend films, and their photovoltaic properties as electron donor material in the photoactive layer are investigated. By incorporating multiple fluorine substituents of benzothiadiazole and inserting two thiophene spacers, the fill factor (FF), open‐circuit voltage, and short‐circuit current density are dramatically improved in comparison with fluorinated‐free materials. With the solvent vapor annealing treatment, further enhancement in charge carrier mobility and power conversion efficiency (PCE) are achieved. Finally, a high PCE of 8.1% with very‐high FF of 0.76 for BIT‐4F‐T/PC71BM is achieved without additional additive, which is among one of the highest reported for small‐molecules‐based solar cells with PCE over 8%. The results reported here clearly indicate that high PCE in solar cells based small molecules can be significantly increased through careful engineering of the molecular structure and optimization on the morphology of blend films by solvent vapor annealing.

The synthesis of a series of tetrafl uorine-substituted, wide-bandgap, small molecules consisting of various π-conjugated spacers (furan, thiophene, selenophene) between indacenodithiophene as the electron-donating core and the electron-defi cient difl uorobenzothiadiazole unit is reported and the effect of the π-conjugated spacers on the photovoltaic properties is investigated. The alteration of the π-conjugated spacer enables fi ne-tuning of the photophysical properties and energy levels of the small molecules, and allows the adjustment of the charge-transport properties, the morphology of the photoactive fi lms, as well as their photovoltaic properties. Moreover, most of these devices exhibit superior device performances after CH 2 Cl 2 solvent annealing than without annealing, with a high fi ll factor (0.70-0.75 for all cases). Notably, the devices based on the new molecule BIT4FTh (with thiophene as the spacer) show an outstanding PCE of 8.7% (with an impressive FF of 0.75), considering its wide-bandgap (1.81 eV), which is among the highest effi ciencies reported so far for small-molecules-based solar cells. The morphologies of the photoactive layers with/without CH 2 Cl 2 solvent annealing are characterized by atomic force microscopy, transmission electron microscopy and two-dimensional grazing incidence X-ray diffraction analysis. The results reported here clearly indicate that highly effi cient small-molecules-based solar cells can be achieved through rational design of their molecular structure and optimization of the phaseseparated morphology via an adapted solvent-vapor annealing process.

Electronic structure calculations using both ab initio MO and DFT methods, in conjunction with the 6-311++G-(d,p), 6-311++G(3df,2p), and aug-cc-pVTZ basis sets, have been applied to investigate the energies and structures of the lowest-lying triplet states of the series of five parent nucleotide RNA and DNA bases including uracil, thymine, cytosine, guanine, and adenine and the halogenated 5X and 6X-substituted uracils (X ) F, Cl, and Br). The singlet-triplet gap ∆E ST of uracil was evaluated using different functionals (B3LYP, B3P86, B3PW91, BP97-1, HCTH). MP2 and CCSD(T) methods were considered for uracil and thymine. For other bases, only B3LYP computations were performed. Computed results agree relatively well with those derived from recent electron impact study (Abouaf et al., Chem. Phys. Lett. 2003, 381, 486). For each base, the vertical triplet state is calculated at 3.5-3.8 eV above the corresponding singlet ground state but about 1 eV below the first excited singlet. Although geometrical relaxation of triplet structures involving out-of-plane distortions of hydrogen atoms leads to a stabilization of 0.7-0.8 eV, the triplet state is of (π* r π) character. The ∆E ST values are evaluated as follows (values in eV and referred to S 0 ): uracil, 3.63 (vertical, exp, 3.65 ( 0.05)/3.00 (adiabatic); thymine, 3.50 (exp, 3.60 ( 0.05)/2.85; cytosine, 3.60/3.09; guanine, 3.84/3.06; adenine, 3.71/3.09. For uracil, halogen substitution at C(5) tends to reduce the ∆E ST value by up to 0.3 eV whereas C(5) methylation and C(6) halogenation induce only small changes. A vibrational analysis pointed out that the frequencies associated with the main normal modes such as CdO and N-H stretching motions are only slightly shifted upon excitation.

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A family of narrow band gap extended πconjugated D 2 -A 2 -D 1 -A 1 -D 1 -A 2 -D 2 type small molecules based on diketopyrrolopyrrole derivatives as the stronger acceptor core (A 1 ) coupled with indacenodithiophene (IDT; D 1 ) and difluorobenzothiadiazole (A 2 ) are synthesized, and their properties as donor materials in solution-processed smallmolecule organic solar cells are investigated. The impacts of replacing the thiophene ring by a more electron-deficient thiazole ring and inserting thiophene spacer between electrondonating (D 1 ) and electron-accepting (A 1 and A 2 ) aromatic moieties on bulk properties, such as the photophysical properties, the HOMO/LUMO energy level, charge carrier mobilities, and the morphologies of blend films, as well as optimization on device performance via solvent vapor annealing are investigated. NDPPFBT shows outstanding efficiencies up to 7.00% after THF vapor annealing for 60 s because of a very high fill factor (FF) of 0.73 and high V oc of 0.89 V. The reported efficiency is among one of the highest values for small-molecules-based organic solar cells from an electronaccepting unit as core and appears as the first diketopyrrolopyrrole-based small-molecule bulk-heterojunction organic solar cells with PCE over 7% with high FF and V oc .

The endoplasmic reticulum (ER) has a central role in the fine-tuning of environmental and internal stimuli. We herein report a ratiometric fluorescent probe, α-Naph, capable of determining basal HO in the ER. The probe specifically responds to HO. The limit of detection of the probe is as low as 38 nM, making it a feasible sensor to image intracellular basal HO. In addition, utilizing its ratiometric property, we are able to measure the concentration of HO in the ER quantitatively, eliminating the error caused by the probe concentration and environment. The intracellular concentration of HO in the ER is calculated to be 0.692 μM under normal conditions and 1.26 μM under the stimulation of phorbol myristate acetate.

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