Cyclic Thiourea/Urea Functionalized Triphenylamine-Based Dyes for High-Performance Dye-Sensitized Solar Cells

Six cyclic thiourea/urea functionalized triphenylamine-based dyes (<b>AZ1</b>–<b>AZ6</b>) containing 2-cyanoacrylic acid as an acceptor and various linkers (phenyl, biphenyl, and bithiophene) were synthesized. They exhibited high photovoltaic performance owing to an improved short-circuit photocurrent density (<i>J</i>_sc) and open-circuit voltage (<i>V</i>_oc). Among them, <b>AZ6</b> bearing a cyclic thiourea group and bithiophene linker showed the highest power conversion efficiency (PCE) up to 7.29%, which was comparable to that of <b>N719</b> (PCE = 7.36%)

Lateral substituent effects on UV stability of high-birefringence liquid crystals with the diaryl-diacetylene core: DFT/TD-DFT study

<p>To study the effect of the lateral substituents on the UV stability of high birefringence liquid crystals (LCs), computational chemistry was used to examine a series of high birefringence LCs based on a diphenyl-diacetylene (DPDA) central core, thiophene segments as elongated π-conjugated units and four electron-withdrawing groups (-F, -CF₃, -OCF₃, -CN) as lateral substituents. In the present study, geometry optimisations have been performed using the DFT/B3LYP/6-311G (d, p) method. Out of a series of functional and basis sets examined, the functional ωB97X-D and basis set 6-31G (d, p) are most successful in predicting charge transfer absorption. The theoretical study indicates that the enhancement of UV stability is related with the types, numbers and positions of the lateral substituents. The calculated results indicate that the electron-withdrawing groups can shorten triple bond length, decrease energy gap value and increase the absorption maxima of the high-Δ<i>n</i> LCs, which is beneficial for good UV stability. With the introduction of increasing lateral electron-withdrawing substituent numbers, the DPDA derivatives would further improve UV stability. This work may provide an effective solution for the obstacle existed in the high-Δ<i>n</i> LCs with DPDA structures and pave a way for their applications in LC photonics.</p

Data File 1: Improving UV stability of tolane-liquid crystals in photonic applications by the ortho fluorine substitution

Phase transition temperatures (T/ oC) and associated transition enthalpy values (kJ mol-1) in parentheses for compounds 3Fn and 4Fn. Originally published in Optical Materials Express on 01 January 2016 (ome-6-1-97

Nematic mesophase enhanced via lateral monofluorine substitution on benzoxazole-liquid crystals

<p>Fluorine is widely used as a lateral substituent to modify the physical properties of liquid crystals. Here, laterally monofluorinated compounds, 2-(4ʹ-alkoxy-2-fluorobiphenyl-4-yl)-benzoxazole derivatives (nPPF(2)Bx) bearing different substituents (H, CH₃, NO₂, coded as nPPF(2)BH, nPPF(2)BM and nPPF(2)BN, respectively) at 5-position, were synthesised and characterised. It is interesting to note that these only display enantiotropic nematic mesophases with mesophase ranges of 12–28°C and 13–45°C on heating and cooling for nPPF(2)BH, 46–97°C and 62–120°C for nPPF(2)BM and 82–108°C and 87–113°C for nPPF(2)BN, which are very different from the corresponding monofluorine-substituted analogue (compounds I) with enantiotropic smectic or smectic/nematic mesophases. The enhanced nematic mesophase is attributed to the reduced π–π interaction/conjugation resulting from the twisted structure of the molecule caused by the introduction of a fluorine atom into the inter-ring of the biphenyl unit. These results suggest that modification of the monofluorine substituent position is an effective method to improve the nematic mesophase in benzoxazole-liquid crystals.</p

Structural Modulation from 1D Chain to 3D Framework: Improved Thermostability, Insensitivity, and Energies of Two Nitrogen-Rich Energetic Coordination Polymers

Two new energetic coordination polymers (CPs) [Pb­(BT)­(H₂O)₃]_<i>n</i> (<b>1</b>) and [Pb₃(DOBT)₃(H₂O)₂]_<i>n</i>·(4H₂O)_<i>n</i> (<b>2</b>) with 1D and 3D structures were synthesized by employing two rational designed ligands, 1H,1′H-5,5′-bitetrazole (H₂BT) and 1H,1′H-[5,5′-bitetrazole]-1,1′-diol ligands (DHBT), respectively. Thermal analyses and sensitivity tests show that the 3D architecture reinforces the network of <b>2</b> which has higher thermal stability and lower sensitivity than that of <b>1</b>. Through oxygen-bomb combustion calorimetry the molar enthalpy of formation of <b>2</b> is derived to be much higher than that of <b>1</b> as well as the reported CPs. Herein, more importantly, the heats of detonation (Δ<i>H</i>_det) were calculated according to the decomposition products of TG-DSC-MS-FTIR simultaneous analyses for the first time. The calculated results show that Δ<i>H</i>_det of <b>2</b> is 23% higher than that of <b>1</b>. This research demonstrates that 3D energetic CP with outstanding energetic properties can be obtained through efficient and reasonable design

Structural Modulation from 1D Chain to 3D Framework: Improved Thermostability, Insensitivity, and Energies of Two Nitrogen-Rich Energetic Coordination Polymers

Two new energetic coordination polymers (CPs) [Pb­(BT)­(H₂O)₃]_<i>n</i> (<b>1</b>) and [Pb₃(DOBT)₃(H₂O)₂]_<i>n</i>·(4H₂O)_<i>n</i> (<b>2</b>) with 1D and 3D structures were synthesized by employing two rational designed ligands, 1H,1′H-5,5′-bitetrazole (H₂BT) and 1H,1′H-[5,5′-bitetrazole]-1,1′-diol ligands (DHBT), respectively. Thermal analyses and sensitivity tests show that the 3D architecture reinforces the network of <b>2</b> which has higher thermal stability and lower sensitivity than that of <b>1</b>. Through oxygen-bomb combustion calorimetry the molar enthalpy of formation of <b>2</b> is derived to be much higher than that of <b>1</b> as well as the reported CPs. Herein, more importantly, the heats of detonation (Δ<i>H</i>_det) were calculated according to the decomposition products of TG-DSC-MS-FTIR simultaneous analyses for the first time. The calculated results show that Δ<i>H</i>_det of <b>2</b> is 23% higher than that of <b>1</b>. This research demonstrates that 3D energetic CP with outstanding energetic properties can be obtained through efficient and reasonable design

Structural Modulation from 1D Chain to 3D Framework: Improved Thermostability, Insensitivity, and Energies of Two Nitrogen-Rich Energetic Coordination Polymers

Two new energetic coordination polymers (CPs) [Pb­(BT)­(H₂O)₃]_<i>n</i> (<b>1</b>) and [Pb₃(DOBT)₃(H₂O)₂]_<i>n</i>·(4H₂O)_<i>n</i> (<b>2</b>) with 1D and 3D structures were synthesized by employing two rational designed ligands, 1H,1′H-5,5′-bitetrazole (H₂BT) and 1H,1′H-[5,5′-bitetrazole]-1,1′-diol ligands (DHBT), respectively. Thermal analyses and sensitivity tests show that the 3D architecture reinforces the network of <b>2</b> which has higher thermal stability and lower sensitivity than that of <b>1</b>. Through oxygen-bomb combustion calorimetry the molar enthalpy of formation of <b>2</b> is derived to be much higher than that of <b>1</b> as well as the reported CPs. Herein, more importantly, the heats of detonation (Δ<i>H</i>_det) were calculated according to the decomposition products of TG-DSC-MS-FTIR simultaneous analyses for the first time. The calculated results show that Δ<i>H</i>_det of <b>2</b> is 23% higher than that of <b>1</b>. This research demonstrates that 3D energetic CP with outstanding energetic properties can be obtained through efficient and reasonable design

Highly Efficient Solar Cells Based on the Copolymer of Benzodithiophene and Thienopyrroledione with Solvent Annealing

Highly efficient PBDTTPD-based photovoltaic devices with the configuration of ITO/poly­(3,4-ethylenedioxythiophene)-poly­(styrenesulfonate) (PEDOT:PSS)/PBDTTPD: methanofullerene (6,6)-phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) (weight ratio being from 1:1 to 1:4)/LiF (5 Å)/Al (100 nm), were realized with ortho-dichlorobenzene (DCB) solvent annealing treatment. It was revealed that the best photovoltaic device was obtained when the blend ratio of PBDTTPD:PC₆₁BM was modulated to be 1:2 and processed with DCB solvent annealing for 12 h. The short-circuit current density (<i>J</i>_sc) and power conversion efficiency (PCE) values were measured to be 10.52 mA/cm² and 4.99% respectively, which were both higher than the counterparts treated with chlorobenzene (CB) solvent annealing or the thermal annealing. Atomic force microscopy measurements of the active layer after solvent annealing treatment were also carried out. The phase separation length scale of the PBDTTPD:PC₆₁BM­(1:2) layer was comparable to the exciton diffusion length when the active layer was treated under DCB solvent annealing, which facilitated effective exciton dissociation and carrier diffusion in the active layer. Therefore, highly efficient PBDTTPD-based photovoltaic devices could be achieved with DCB solvent annealing, which indicated that solvent annealing with proper solvent might be an easily processed, low-cost, and room-temperature alternative to thermal annealing for polymer solar cells