Synthesis and photovoltaic properties of D-A copolymers based on alkylthio-thiophene or alkylthio-selenophene-BDT donor unit and DPP acceptor unit

Two new 2D-conjugated D-A copolymers, PBDTT-S-DPP and PBDTSe-S-DPP, based on benzodithiophene (BDT) donor unit with alkylthio-thiophene or alkylthio-selenophene conjugated side chains and 2,5-bis(2-butyloctyl)-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione) (DPP) acceptor unit, were synthesized for the application as donor materials in polymer solar cells (PSCs). The two polymers were characterized by absorption spectroscopy, cyclic voltammetry, thermogravimetric analysis, theoretical calculation with density functional theory, X-ray diffraction and photovoltaic measurements. The results show that the alkylthio-thiophene/selenophene side groups on BDT unit and intramolecular hydrogen bonding interaction in DPP acceptor unit play important roles in affecting the absorption, HOMO energy levels, molecular planarity and the crystallinity of the polymers. The PSCs based on PBDTT-S-DPP or PBDTSe-S-DPP as donor and PC₇₁BM as acceptor demonstrate power conversion efficiency (PCE) of 5.62% and 5.01%, with relatively higher V_oc of 0.79 V and 0.76 V, respectively.     

D-A copolymers based on dithienosilole and phthalimide for photovoltaic materials

Two D-A copolymers containing dithienosilole (DTS) donor unit and phthalimide (Ph) acceptor unit, PDTSPh and PDTSBTPh, were synthesized by the Pd-catalyzed Stille-coupling method. The copolymers have a strong absorption ranging from 350 to 650 nm, exhibit good solubility and thermal stability. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels of the copolymers determined by cyclic voltammetry were about −5.2 and −3.0 eV, respectively. The power conversion efficiency of the polymer solar cells based on PDTSBTPh:PC₇₀BM (1:2, w/w) reached 2.1% with open-circuit voltage of 0.83 V and a short-circuit current of 6.27 mA/cm², under the illumination of AM1.5, 100 mW/cm².     

Symbols of terror: The witch/vampire, the spider, and the shark.

Three symbols of terror are examined as representations of preoedipal conflicts that intrude upon conscious awareness and. interfere with current functioning. To understand each of these symbols and their origins in a state of chronic terror, it is necessary to understand the complete life history of the patient. All three symbols--the witch/vampire, the spider, and the shark--relate to earliest experiences within the parent/infant dyad. We suggest that although all three symbols relate to the dimension of oral aggression, they can be placed conceptually along a continuum of distance from the quality of humanness. Clinical examples are given to illustrate the use of these symbols by patients in treatment and their theoretical implications. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

圆锥曲线仪的计算机辅助设计方法

根据平面机构瞬心线的原理和利用加“双滑块二级组”绘制平面机构定瞬心线的方法，论述了一种圆锥曲线仪的计算机辅助设计方法，文中编制了程序设计框图，并通过实例绘制了圆锥曲线．     

Synthesis and properties of tetrathiafulvalene-porphyrin assemblies

Two donor-σ-acceptor molecular systems incorporating tetrathiafulvalene (TTF) and tetraphenylporphyrin (TPP) units, TTF-TPP (dyad 1) and TTF-TPP-TTF (triad 2), were synthesized. Both dyad 1 and triad 2 and their synthetic intermediates have been characterized by ¹H nuclear magnetic resonance (¹H NMR) and mass spectrography (MS). Their ultraviolet and visible spectroscopy (UV-Vis) and cyclic voltammetry (CV) showed negligible intramolecular charge transfer interaction in their ground states. Their fluorescence intensity was strongly quenched compared with TPP, which implied the photoinduced electron transfer occurred from the TTF unit to the TPP unit in the excited state. On the other hand, their fluorescence intensity could be modulated by sequential oxidation of the TTF unit using chemical methods, which exhibited their potential application in fluorescence molecular switch.     

New m-alkoxy-p-fluorophenyl difluoroquinoxaline based polymers in efficient fullerene solar cells with high fill factor

Two new donor (D) - acceptor (A) copolymers, named m-O-p-F-DFQx-BDT (OFQx-T) and m-EH-p-F-DFQx-BDT (EHFQx-T), which were based on meta-octyloxy-para-fluorophenyl and meta-ethylhexyloxy-para-fluorophenyl difluoroquinoxaline as acceptor units (O-DFQx/EH-DFQx) and alkylthienyl substituted benzodithiophene (BDT) as a donor unit, were designed and synthesized. EHFQx-T had higher absorption coefficient than OFQx-T which contributed to larger short-circuit current density (J_sc). EHFQx-T showed a lower the highest occupied molecular orbital (HOMO) which is beneficial for the voltage open-circuit (V_oc). The polymer solar cells (PSCs) based OFQx-T:PC₇₁BM and EHFQx-T:PC₇₁BM blended film as active layer showed high power conversion efficiency (PCE) of 7.60% and 8.44%, respectively, with 1,8-diiodooctane (DIO) solvent additive treatment. More importantly, OFQx-T:PC₇₁BM and EHFQx-T:PC₇₁BM had good fill factor (FF), especially the FF of OFQx-T:PC₇₁BM was over 70%. The high FF contributed to obtain high PCEs for OFQx-T and EHFQx-T. The more balanced and higher charge mobility, smaller geminate recombination and suitable nanoscale phase separation size of EHFQx-T demonstrate that changing octyl chain to ethylhexyl chain in DFQx acceptor unit is efficient to improve photovoltaic properties in fullerene solar cells.     

Highly sensitive near infrared organic phototransistors based on conjugated polymer nanowire networks

Highly sensitive near-infrared (NIR) organic phototransistors (OPTs) were fabricated using nanowire network based on a narrow bandgap donor-acceptor (D-A) polymer as the photoactive channel. The D-A polymer nanowire network-based NIR-OPTs exhibit high responsivity of ∼246 A/W under an NIR illumination source (850 nm) with a light intensity of ∼0.1 mW/cm². This value is over one order of magnitude higher than that of the structurally identical planar D-A polymer thin film OPTs. The high performance of the nanowire network-based phototransistors is attributed to the excellent hole transport ability, reduced density of the structural defects in the polymer nanowires, and improved contact at the channel layer/electrode interfaces. The high sensitivity and low cost solution-fabrication process render this OPT technology appealing and practically viable for application in large area NIR sensors.     

When training with a partner is inferior to training alone: The importance of dyad type and interaction quality.

Dyad training, where trainees learn in pairs but ultimately perform individually, has been shown to be an effective method for training some skills. The effectiveness of this approach, however, may be tied to the type of task to be trained and the quality of the interaction in the dyad. We report two studies on the effectiveness of dyad training and the role of metacognitive activity for learning a software program. In Study 1, participants completed training alone or with a partner. Performance was assessed individually immediately after training and again after a 1-week nonuse interval. Results of Study 1 suggested that learning retention is superior when people are trained individually. Study 2 examined performance for individuals, task-switching dyads, and interdependent dyads. Results also showed that performance for individuals was superior to dyads and that the type of dyad collaboration did not affect performance. However, partner-prompted metacognitive activity was helpful for interdependent dyads and harmful for task-switching dyads, suggesting that the quality of collaboration varies by dyad type. Our findings suggest that dyad training may not be effective for all types of tasks. Possible boundary conditions for effective dyad training are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)