Xingang Zhao

Significant progress has been achieved in the preparation of semiconducting polymers over the past two decades, and successful commercial devices based on them are slowly beginning to enter the market. However, most of the conjugated polymers are hole transporting, or p-type, semiconductors that have seen a dramatic rise in performance over the last decade. Much less attention has been devoted to electron transporting, or n-type, materials that have lagged behind their p-type counterparts. Organic electron transporting materials are essential for the fabrication of organic p-n junctions, organic photovoltaic cells (OPVs), n-channel organic field-effect transistors (OFETs), organic light-emitting diodes (OLEDs) and complementary logic circuits. In this critical review we focus upon recent developments in several classes of electron transporting semiconducting polymers used in OLEDs, OFETs and OPVs, and survey and analyze what is currently known concerning electron transporting semiconductor architecture, electronic structure, and device performance relationships (87 references).

Binary additives synergistically boost the power conversion efficiency of all-polymer solar cells up to 3.45%. The nonvolatile additive PDI-2DTT suppresses aggregation of the acceptor PPDIDTT and enhances donor/acceptor mixing, while the additive DIO facilitates aggregation and crystallization of the donor PBDTTT-C-T as well as improves phase separation. Combination of DIO and PDI-2DTT leads to suitable phase separation and improved and balanced charge transport, which is beneficial to efficiency enhancement.

Severe acute respiratory syndrome (SARS) is an acute infectious disease with significant mortality. A typical clinical feature associated with SARS is pulmonary fibrosis and the associated lung failure. However, the underlying mechanism remains elusive. In this study, we demonstrate that SARS-associated coronavirus (SARS-CoV) nucleocapsid (N) protein potentiates transforming growth factor-beta (TGF-beta)-induced expression of plasminogen activator inhibitor-1 but attenuates Smad3/Smad4-mediated apoptosis of human peripheral lung epithelial HPL1 cells. The promoting effect of N protein on the transcriptional responses of TGF-beta is Smad3-specific. N protein associates with Smad3 and promotes Smad3-p300 complex formation while it interferes with the complex formation between Smad3 and Smad4. These findings provide evidence of a novel mechanism whereby N protein modulates TGF-beta signaling to block apoptosis of SARS-CoV-infected host cells and meanwhile promote tissue fibrosis. Our results reveal a novel mode of Smad3 action in a Smad4-independent manner and may lead to successful strategies for SARS treatment by targeting the TGF-beta signaling molecules.

Air‐stable and soluble tetrabutylammonium fluoride (TBAF) is demonstrated as an efficient n‐type dopant for the conjugated polymer ClBDPPV. Electron transfer from F − anions to the π‐electron‐deficient ClBDPPV through anion–π electronic interactions is strongly corroborated by the combined results of electron spin resonance, UV–vis–NIR, and ultraviolet photoelectron spectroscopy. Doping of ClBDPPV with 25 mol% TBAF boosts electrical conductivity to up to 0.62 S cm −1 , among the highest conductivities that have been reported for solution‐processed n‐type conjugated polymers, with a thermoelectric power factor of 0.63 µW m −1 K −2 in air. Importantly, the Seebeck coefficient agrees with recently published correlations to conductivity. Moreover, the F − ‐doped ClBDPPV shows significant air stability, maintaining the conductivity of over 0.1 S cm −1 in a thick film after exposure to air for one week, to the best of our knowledge the first report of an air‐stable solution‐processable n‐doped conductive polymer with this level of conductivity. The result shows that using solution‐processable small‐anion salts such as TBAF as an n‐dopant of organic conjugated polymers possessing lower LUMO (lowest unoccupied molecular orbital), less than −4.2 eV) can open new opportunities toward high‐performance air‐stable solution‐processable n‐type thermoelectric (TE) conjugated polymers.