Photovoltaic Performance Improvement of D–A Copolymers Containing Bithiazole Acceptor Unit by Using Bithiophene Bridges

Two bithiophene-bridged D–A copolymers, PDTSBTBTz and PBDTBTBTz, based on bithiazole acceptor unit and dithienosiole (DTS) or benzodithiophene (BDT) donor unit, were synthesized by the Pd-catalyzed Stille-coupling reaction. The two copolymers exhibit good thermal stability, strong absorption in the visible region, and relatively lower HOMO energy level at ca. −5.10 eV. The hole mobilities of PDTSBTBTz and PBDTBTBTz measured by SCLC method are 1.85 × 10^–3 and 1.77 × 10^–3 cm²/(V s), respectively. Power conversion efficiency (PCE) of the polymer solar cell (PSC) based on PDTSBTBTz: PC₇₀BM (1:1, w/w) was 3.82% with <i>J</i>_sc = 8.68 mA/cm², <i>V</i>_oc = 0.72 V, and FF = 0.611, under the illumination of AM1.5, 100 mW/cm². In contrast, the PCE of the PSC based on PBDTBTBTz:PC₇₀BM (1:1, w/w) reached 4.46% with <i>J</i>_sc = 9.01 mA/cm², <i>V</i>_oc = 0.82 V, and FF = 0.603. These results indicate that bithiophene-bridged D–A copolymers are promising photovoltaic donor materials for the application in PSCs

Conjugated Side-Chain-Isolated D–A Copolymers Based on Benzo[1,2‑<i>b</i>:4,5‑<i>b</i>′]dithiophene-<i>alt</i>-dithienylbenzotriazole: Synthesis and Photovoltaic Properties

Conjugated side-chain-isolated D–A copolymers, based on the donor unit of benzodithiophene (BDT) with a thiophene-conjugated side chain, thiophene π bridge, and the acceptor unit of benzotriazole (BTA) with or without fluorine substitution (PBDT-FBTA and PBDT-HBTA), were designed and synthesized for elucidating their structure–property relationships. The copolymer films demonstrated well-defined absorption peaks with steep absorption edges, consistent with their rigid and ordered structures in the solid films. The substitution of a thiophene-conjugated side chain on the BDT unit in the copolymers aroused 15-nm red-shifted absorption in comparison with its polymer analogues with alkoxy side chains on the BDT unit. Compared to PBDT-HBTA, PBDT-FBTA with two-fluorine-atom substitution on the BTA unit demonstrated a lower highest occupied molecular orbital energy level, higher hole mobility, and significantly better photovoltaic performance. A polymer solar cell (PSC) based on PBDT-FBTA/PC₇₀BM (1:2, w/w) with a 5% 1,8-diiodooctane additive displayed a power conversion efficiency (PCE) of 6.0% with a <i>J</i>_sc of 11.9 mA cm^–2, a <i>V</i>_OC of 0.75 V, and a fill factor of 67.2%, under the illumination of AM1.5G, 100 mW cm^–2. Even at a thicker active layer of 400 nm, the PSC still demonstrated a higher PCE of 4.74%. The results indicate that PBDT-FBTA is a promising polymer donor material for future application of large-area PSCs

A Novel n-Type Conjugated Polymer DOCN-PPV: Synthesis, Optical, and Electrochemical Properties

A Novel n-Type Conjugated Polymer DOCN-PPV:  Synthesis, Optical, and Electrochemical Propertie

Solution-Processable Gradient Red-Emitting π-Conjugated Dendrimers Based on Benzothiadiazole as Core: Synthesis, Characterization, and Device Performances

A family of gradient π-conjugated dendrimers, in which the 5,5,10,10,15,15-hexahexyltruxene unit is employed as the node, oligo(thienylethynylene)s (OTEs) are employed as light-harvesting branching units, and a 4,7-diaryl-2,1,3-benzothiadiazole is employed as the core, have been developed through the Sonogashira reaction in good yields. All dendrimers were fully characterized by 1H and 13C NMR, elemental analysis, and MALDI-TOF MS. Investigation of their steady-state and time-resolved photophysical properties revealed that the gradient dendritic scaffold resulted in efficient energy transfer and strong red emission. On the basis of the good solubility and excellent film forming properties, single-layer red-emitting diodes using these dendrimers as the active materials were fabricated by a simple solution spin-coating process. The moderate device performance was achieved; for example, the maximum luminance of 1290 cd/m2 with a maximum luminescence efficiency of 1.07 cd/A was performed from BTDyn

Understanding the Fast-Triggering Unfolding Dynamics of FK-11 upon Photoexcitation of Azobenzene

Photoswitchable molecules can control the activity and functions of biomolecules by triggering conformational changes. However, it is still challenging to fully understand such fast-triggering conformational evolution from nonequilibrium to equilibrium distribution at the molecular level. Herein, we successfully simulated the unfolding of the FK-11 peptide upon the photoinduced trans-to-cis isomerization of azobenzene based on the Markov state model. We found that the ensemble of FK-11 contains five conformational states, constituting two unfolding pathways. More intriguingly, we observed the microsecond-scale conformational propagation of the FK-11 peptide from the fully folded state to the equilibrium populations of the five states. The computed CD spectra match well with the experimental data, validating our simulation method. Overall, our study not only offers a protocol to study the photoisomerization-induced conformational changes of enzymes but also could orientate the rational design of a photoswitchable molecule to manipulate biological functions

Enhancing Photovoltaic Performance of Copolymers Containing Thiophene Unit with D–A Conjugated Side Chain by Rational Molecular Design

Rational molecular design of conjugated polymers and cautious optimization of morphologies of the active layer are critical for developing high performance polymer solar cells (PSCs). In this work, we designed and synthesized a new thiophene monomer TBTF attaching donor–acceptor (D–A) conjugated side chain with fluorinated 4,7-dithien-5-yl-2,1,3-benzodiathiazole (BTF) as acceptor unit, and synthesized two new two-dimension-conjugated (2D-conjugated) copolymers, <b>P­(BDT-TBTF)</b> and <b>P­(BDT-TBTF/DPP)</b>, for the application as donor materials in PSCs. <b>P­(BDT-TBTF)</b> is a new side chain D–A copolymer of benzodithiophene (BDT) and TBTF units, and <b>P­(BDT-TBTF/DPP)</b> is a ternary D–A copolymer of BDT, TBTF and pyrrolo­[3,4-c]­pyrrole-1,4-dione (DPP) units. The introduction of TBTF unit with D–A conjugated side chain and DPP unit forming the ternary copolymer provides the opportunity to tune the optoelectronic properties of the resulting polymers. As expected, the binary copolymer <b>P­(BDT-TBTF)</b> shows an enhanced absorption coefficient and lower-lying HOMO energy level, and the ternary copolymer <b>P­(BDT-TBTF/DPP)</b> possesses a small bandgap and quite broad absorption band matched well with solar spectrum. These features are beneficial to achieving reasonable high short-circuit current (<i>J</i>_sc) and high open-circuit voltage (<i>V</i>_oc). Bulk-heterojunction PSCs based on <b>P­(BDT-TBTF)</b> showed an initial power conversion efficiency (PCE) of 5.66% with a high <i>V</i>_oc of 0.88 V and a <i>J</i>_sc of 11.23 mA cm^–2, whereas <b>P­(BDT-TBTF/DDP)</b> gave a PCE of 3.51% along with a higher <i>J</i>_sc of 13.15 mA cm^–2. The <i>J</i>_sc and PCE of the devices were further improved by a simple methanol treatment, to 13.21 mA cm^–2 and 6.21% for <b>P­(BDT-TBTF)</b> and 14.56 mA cm^–2 and 5% for <b>P­(BDT-TBTF/DPP),</b> respectively. To the best of our knowledge, the PCE of 6.21% is the highest value reported for PSCs based on side chain D–A copolymers to date. This is a good example for a subtle tuning absorption properties, energy levels, charge transport and photovoltaic properties of the polymers by rational molecular design

Indene−C₆₀ Bisadduct: A New Acceptor for High-Performance Polymer Solar Cells

Polymer solar cells (PSCs) are commonly composed of a blend film of a conjugated polymer donor and a soluble C60 derivative acceptor sandwiched between an ITO anode and a low-workfunction metal cathode. Poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) are the most widely used donor and acceptor materials, respectively. However, the low LUMO energy level of PCBM limits the open circuit voltage (Voc) of the P3HT-based PSCs to ca. 0.6 V. Here we synthesized a new soluble C60 derivative, indene−C60 bisadduct (ICBA), with a LUMO energy level 0.17 eV higher than that of PCBM. The PSC based on P3HT with ICBA as acceptor shows a higher Voc of 0.84 V and higher power conversion efficiency (PCE) of 5.44% under the illumination of AM1.5, 100 mW/cm2, while the PSC based on P3HT/PCBM displays a Voc of 0.58 V and PCE of 3.88% under the same experimental conditions. The results indicate that ICBA is an alternative high-performance acceptor and could be widely used in high-performance PSCs

Supplemental_Material – Supplemental material for MicroRNA-373 promotes the development of esophageal squamous cell carcinoma by targeting <i>LATS2</i> and <i>OXR1</i>

Supplemental material, Supplemental_Material for MicroRNA-373 promotes the development of esophageal squamous cell carcinoma by targeting LATS2 and OXR1 by Li Wang, Lifeng Wang, Weidong Chang, Yongfang Li and Linsong Wang in The International Journal of Biological Markers</p

Understanding the Fast-Triggering Unfolding Dynamics of FK-11 upon Photoexcitation of Azobenzene

Photoswitchable molecules can control the activity and functions of biomolecules by triggering conformational changes. However, it is still challenging to fully understand such fast-triggering conformational evolution from nonequilibrium to equilibrium distribution at the molecular level. Herein, we successfully simulated the unfolding of the FK-11 peptide upon the photoinduced trans-to-cis isomerization of azobenzene based on the Markov state model. We found that the ensemble of FK-11 contains five conformational states, constituting two unfolding pathways. More intriguingly, we observed the microsecond-scale conformational propagation of the FK-11 peptide from the fully folded state to the equilibrium populations of the five states. The computed CD spectra match well with the experimental data, validating our simulation method. Overall, our study not only offers a protocol to study the photoisomerization-induced conformational changes of enzymes but also could orientate the rational design of a photoswitchable molecule to manipulate biological functions

Liquid Crystal Helps ZnO Nanoparticles Self-Assemble for Performance Improvement of Hybrid Solar Cells

We offer a novel approach to improve the performance of poly 3-hexylthiophene (P3HT)/ZnO hybrid photovoltaic devices by binding the 4,7-diphenyl-2,1,3-benzothiadiazole-based liquid crystal (LC) with a monothiol end group onto the surface of ZnO nanoparticles (LC-ZnO). The attachment of LC onto ZnO nanoparticles’ surfaces can improve the dispersion of ZnO nanoparticles and can endow the ZnO nanoparticles self-assembled behavior upon annealing at LC state temperature (160 °C). By use of the LC-ZnO as electron acceptors in hybrid solar cells enhances the order and crystallinity of P3HT chains and evolves the microstructure of P3HT/LC-ZnO blend, enabling short-circuit current density (<i>J</i>_sc) to be increased. More interestingly, the order of the P3HT/LC-ZnO blend morphology is significantly enhanced after thermal treatment at 160 °C, indicating that the spontaneous assembly of the LC-ZnO pushes P3HT chains to form oriented nanodispersing structure with highly oriented channel layers upon only heating at LC states, leading to the improved power conversion efficiency by 1.8 fold compared with the device based on P3HT/ZnO, demonstrating that the described self-assembled LC-ZnO hybrids represent a promising strategy toward nanoscale controlled bulk heterojunction solar cells