Licheng Tan

A Facile approach to NiCoO2 intimately standing on nitrogen doped graphene sheets by one-step hydrothermal synthesis for supercapacitors

Novel composites based on cubic binary nickel cobaltite oxide intimately standing on nitrogen doped reduced graphene sheets (NRGO–NiCoO2) were prepared by a simple one step hydrothermal synthesis. The results showed that the highly crystalline NiCoO2 nanoparticles with a uniform size were homogeneously distributed on nitrogen-doped reduced graphene sheets (NRGO). The homogeneous composites combined NiCoO2, which has high specific capacitance, and NRGO, which has efficient electronic conductivity, to consequently yield low resistance conduction between metal oxides and graphene due to a barrier-free contact. The synergistic effect of NRGO substrates and NiCoO2 nanoparticles promoted the electrochemical performance of the composites. The electrochemical properties of NRGO–NiCoO2 can be easily tuned by altering the amount of nitrogen-composed reducer. The NRGO–NiCoO2 composites exhibited a remarkable specific capacitance of 508 F g−1 at 0.5 A g−1, an excellent rate performance in cyclic voltammetry test (from 5 to 90 mV s−1) and good galvanostatic charge–discharge measurements (from 0.5 to 20 A g−1). The capacitance was maintained at 93% of the original value even after 2000 cycles. The flexible devices were assembled, which possessed a specific capacitance of 58 F g−1 at 0.5 A g−1. This facile one-step strategy is an effective method for developing excellent supercapacitor electrodes.

Triple Dipole Effect from Self‐Assembled Small‐Molecules for High Performance Organic Photovoltaics

A novel triple dipole effect has been observed for Cl-assisted self-assembled small-molecules on ITO substrate, and a highest polymer solar cell performance of 9.2% is obtained.

A novel thermal and pH responsive drug delivery system based on ZnO@PNIPAM hybrid nanoparticles

A smart ZnO@PNIPAM hybrid was prepared by grafting thermal responsive poly(N-isopropylacrylamide) (PNIPAM) on zinc oxide (ZnO) nanoparticles via surface-initiated atom transfer radical polymerization (ATRP). The thermal gravimetric analysis (TGA) shows that the grafting amount of PNIPAM was about 38%, and the SEM images show that the PNIPAM chains can prevent the aggregation of ZnO nanoparticles. The responsive properties of ZnO@PNIPAM were measured by photoluminescence spectra, and the results demonstrate that the PNIPAM chains grafted on ZnO surfaces can realize reversible thermal responsive and photoluminescence properties. An anticancer drug, doxorubicin (Dox), was used as a model drug and loaded into the hybrid nanoparticles, and an in vitro drug release test implied that ZnO@PNIPAM could work as a thermal responsive drug delivery system. Furthermore, pH sensitive drug releases were carried out in acetate buffer at pH 5.0 and pH 6.0 and in water at pH7.0, and the results showed evident pH dependency, showing its pH responsive properties.

In situ polymerization of ethylenedioxythiophene from sulfonated carbon nanotube templates: toward high efficiency ITO-free solar cells

Sulfonated carbon nanotubes (SCNTs) act as secondary polymerization templates for in situ preparation of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). It essentially reduces the content of insulating PSS, instead of pre- or post-solvent processing, for a highly conductive PEDOT:PSS:SCNT composite electrode. The PEDOT:PSS:SCNT was characterized with regard to its composition, conformation, stability, morphology, optoelectronic devices, and work function behavior. The PEDOT:PSS:SCNT films with a low work function (4.4 eV) and remarkable optoelectronic properties (over 3500 S cm−1, ∼83% transmittance at a 70 nm thickness film) were suitably integrated as a cathode in organic solar cells (OSCs) with a power conversion efficiency (PCE) of 9.91% and perovskite solar cells (PSCs) with a PCE of 13.31%.

Liquid-crystalline ionic liquids modified conductive polymers as a transparent electrode for indium-free polymer solar cells

Ordered microstructure and high conductivity of poly(3,4-ethylenedioxythiophene):poly-(styrene sulfonate) (PEDOT:PSS, commercial product PH1000) films for a transparent anode were obtained by liquid-crystalline ionic liquids modification. By spin-coating 1-hexadecyl-3-methylimidazolium hexafluorophosphate ([C16MIm]PF6) or 1-hexadecyl-3-methylimidazolium tetrafluoroborate ([C16MIm]BF4) on the PH1000 film, half of the insulating PSS on the top surface of PH1000 could be successfully removed and the PEDOT formed an ordered and continuous molecular packing. The conductivity of PH1000 dramatically increased from 0.4 S cm−1 to 1457.7 S cm−1 for PH1000/[C16MIm]PF6 and 1243.8 S cm−1 for PH1000/[C16MIm]BF4. At the same time, spontaneous orientation of the liquid-crystalline ionic liquids with liquid-crystallinity further promoted the ordered packing arrangement of both PH1000 and the active layer. The power conversion efficiency based on PH1000/[C16MIm]PF6 and PH1000/[C16MIm]BF4 as the anode is comparable to that obtained from the device with indium tin oxide (ITO) as the anode. In addition, liquid-crystalline ionic liquids modification is also good for the energy alignment, facilitating charge injection and transport, without any extra hole transport layer. Furthermore, these novel liquid-crystalline ionic liquids modification PH1000 anodes have potential applications in the fabrication of ITO-free large-area flexible printed polymer solar cells.

Recent Progress on the Long‐Term Stability of Perovskite Solar Cells

Abstract As rapid progress has been achieved in emerging thin film solar cell technology, organic–inorganic hybrid perovskite solar cells (PVSCs) have aroused many concerns with several desired properties for photovoltaic applications, including large absorption coefficients, excellent carrier mobility, long charge carrier diffusion lengths, low‐cost, and unbelievable progress. Power conversion efficiencies increased from 3.8% in 2009 up to the current world record of 22.1%. However, poor long‐term stability of PVSCs limits the future commercial application. Here, the degradation mechanisms for unstable perovskite materials and their corresponding solar cells are discussed. The strategies for enhancing the stability of perovskite materials and PVSCs are also summarized. This review is expected to provide helpful insights for further enhancing the stability of perovskite materials and PVSCs in this exciting field.

Versatile MoS2 Nanosheets in ITO-Free and Semi-transparent Polymer Power-generating Glass

Chemical exfoliated ultra-thin MoS2 nanosheets (NSs) with well 2D structure were demonstrated for interfacial layers and Ag nanowires composite transparent electrode in polymer solar cells (PSCs). The smooth and uniform n-type and p-type (after the plasma treatment) MoS2 NSs could improve fill factor of devices and light absorption in active layer. The optimized Ag nanowires–MoS2 NSs (AgNW-MoS2 NSs) transparent electrode presented a low sheet resistance of 9.8 Ω sq−1, and the corresponding transmittance also exhibited a high value of 93.1% at 550 nm. As a result, ITO-free PSCs based on AgNW-MoS2 NSs/n-MoS2 NSs cathode and p-MoS2 NSs/Ag anode achieved a highest PCE of 8.72%. Furthermore, a high efficiency (6.55%), large area and low cost semi-transparent power-generating glass was obtained, after reducing the thickness of top Ag electrode from 100 nm to 30 nm. To our best knowledge, it is the highest performance for semi-transparent PSCs devices reported up to now. The novel semi-transparent power-generating glass showed good performance and color purity for commercial applications in the near future.

Preparation and Hydrolytic Degradation of Poly(hexylene Terephthalate-co-Lactide) co-Polyesters From Melting Polycondensation

To obtain a biodegradable polymer material with satisfactory thermal properties, higher elongation and modulus of elasticity, a series of biodegradable aliphatic/aromatic co-polyesters, poly(hexylene terephthalate-co-lactide) (PHTL), was synthesized via melt polycondensation from dimethyl terephthalate (DMT), 1,6-hexanediol (HDO) and oligo(lactic acid) (OLA) in the presence of titanium (IV) butoxide. The resulting co-polyesters were characterized by proton nuclear magnetic resonance (1H-NMR), differential scanning calorimetry, thermogravimetry and wide-angle X-ray scattering, and their melting temperature, melting heat of fusion, glass-transition temperature (T g) and thermal decomposition temperature (T m) (1.5 wt%) were obtained. Only one T g and two T m values were observed for all samples, and were found to decrease gradually with increase of lactide moieties. By using the relative integral areas of the dyad peaks in the 1H-NMR spectrum of co-polyesters PHTL, the sequence lengths of the hexylene terephthalate (n HT) units in the resultant co-polyesters are 3.5. The PHTL co-polyesters exhibited a pronounced hydrolytic degradability, which increase with the content in lactide units. 1H-NMR analysis of the residue left by evaporation of the mother solution after hydrolytic degradation revealed that the degradation products consisted mostly of lactide and hexylene terephthalate blocks.

In Vivo Evaluation of Butylene Terephthalate-ethylene Oxide-DL, Lactide Polymer as Porous Scaffolds for Tissue Engineering

The copolymers of poly(1,4-butylene terephthalate-co-ethylene oxide-co-DL-lactide), obtained by the transesterification reactions of poly(butylenes terephthalate) with poly(ethylene glycol DL-oligo(lactic acid), were fabricated into porous scaffolds by the established solvent-casting and particulate-leaching technique with NaCl as the porogen. The morphology of the porous scaffolds were investigated by the scanning electron microscopy (SEM), and the pores within the scaffold were proven to be interconnective ranging in size from 200 to 400 mm. The human bone marrow mesenchymal stem cells (MSC) seeded on the scaffolds were confirmed to survive and proliferate within the pores of the scaffold with the observation by immunofluorescence microscope and SEM. In vivo implantation of MSC-seeded scaffolds into athymic nude mice showed significant tissue formation in the subcutaneous sites of the immunodeficient mice at 3, 4, 6, and 9 weeks. The results indicate that the scaffolds were biocompatible with MSC and the host tissue in vitro and in vivo.The copolymers of poly(1,4-butylene terephthalate-co-ethylene oxide-co-DL-lactide), obtained by the transesterification reactions of poly(butylenes terephthalate) with poly(ethylene glycol DL-oligo(lactic acid), were fabricated into porous scaffolds by the established solvent-casting and particulate-leaching technique with NaCl as the porogen. The morphology of the porous scaffolds were investigated by the scanning electron microscopy (SEM), and the pores within the scaffold were proven to be interconnective ranging in size from 200 to 400 μm. The human bone marrow mesenchymal stem cells (MSC) seeded on the scaffolds were confirmed to survive and proliferate within the pores of the scaffold with the observation by immunofluorescence microscope and SEM. In vivo implantation of MSC-seeded scaffolds into athymic nude mice showed significant tissue formation in the subcutaneous sites of the immunodeficient mice at 3, 4, 6, and 9 weeks. The results indicate that the scaffolds were biocompatible with MSC and th...

Optimization of perovskite by 3D twisted diketopyrrolopyrrole for efficient perovskite solar cells

A solution-processable, aggregation-induced emission-type three-dimensional molecule TPE-DPP4 was synthesized in a facile way. TPE-DPP4 can function as a light-capturer, grain-boundary filler as well as an electron-donor for perovskite + TPE-DPP4 bulk heterojunction hybrid film. The perovskite solar cells obtained with TPE-DPP4 resulted in enhanced power conversion efficiency of 14.1% with 40% enhancement to the device compared with pristine perovskite.