Shiyu Yao

Fluorescent Aptasensor Based on Aggregation-Induced Emission Probe and Graphene Oxide

Recently, a great variety of aggregation-induced emission (AIE)-active molecules has been utilized to design bioprobes for label-free fluorescent turn-on aptasensing with high sensitivity. However, due to nonspecific binding interaction between aptamer and AIE probe, these AIE-based aptasensors have nearly no selectivity, thereby significantly limiting the development. In this work, a 9,10-distyrylanthracene with two ammonium groups (DSAI) is synthesized as a novel AIE probe, and the fluorescent aptasensor based on DSAI and graphene oxide (GO) is developed for selective and sensitive sensing of targeted DNA and thrombin protein. Given its AIE property and high selectivity and sensitivity, this aptasensor can be also exploited to detect other targets.

High-Efficiency Aqueous-Solution-Processed Hybrid Solar Cells Based on P3HT Dots and CdTe Nanocrystals

Without using any environmentally hazardous organic solution, we fabricated hybrid solar cells (HSCs) based on the aqueous-solution-processed poly(3-hexylthiophene) (P3HT) dots and CdTe nanocrystals (NCs). As a novel aqueous donor material, the P3HT dots are prepared through a reprecipitation method and present an average diameter of 2.09 nm. When the P3HT dots are mixed with the aqueous CdTe NCs, the dependence of the device performance on the donor-acceptor ratio shows that the optimized ratio is 1:24. Specifically, the dependence of the device performance on the active-layer thermal annealing conditions is investigated. As a result, the optimized annealing temperature is 265 °C, and the incorporation of P3HT dots as donor materials successfully reduced the annealing time from 1 h to 10 min. In addition, the transmission electron microscopy and atomic force microscopy measurements demonstrate that the size of the CdTe NCs increased as the annealing time increased, and the annealing process facilitates the formation of a smoother interpenetrating network in the active layer. Therefore, charge separation and transport in the P3HT dots:CdTe NCs layer are more efficient. Eventually, the P3HT dots:CdTe NCs solar cells achieved 4.32% power conversion efficiency. The polymer dots and CdTe NCs based aqueous-solution-processed HSCs provide an effective way to avoid a long-time thermal annealing process of the P3HT dots:CdTe NCs layer and largely broaden the donor materials for aqueous HSCs.

Influence of a polyelectrolyte based-fluorene interfacial layer on the performance of a polymer solar cell

A new quaternized ammonium polyfluorene polyelectrolyte poly[3,3′-(2-(3-hexyl-5-(7-(4-hexyl-5-methylthiophen-2-yl)benzo[c][1,2,5]thiadiazol-4-yl)thiophen-2-yl)-7-methyl-9H-fluorene-9,9-diyl)bis(N,N-dimethylpropan-1-amine)]dibromide (PFBTBr) is applied as the cathode interfacial layer of a polymer solar cell based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PC61BM). Electrostatic force microscopy (EFM) measurements of PFBTBr layers demonstrate the formation of the interfacial dipole between the active layer and the cathode by inserting a PFBTBr interfacial layer. Atomic force microscopy (AFM) measurements of PFBTBr layers with varied concentrations show that the morphology of the PFBTBr layer plays a direct, important role in the contact quality between the active layer and the PFBTBr interfacial layer, which can strongly affect the performance of devices. X-ray photoelectron spectroscopy measurements (XPS) indicate that PFBTBr may serve as a protective agent for the active layer against Al-induced degradation, since it prevents hot aluminum atoms from diffusing into the active layer. The power conversion efficiency (PCE) of the PSCs with the PFBTBr layer reaches 3.9% under the illumination of AM 1.5G, 100 mW cm−2, which is 1.6 times higher in comparison with that (2.4%) of the device without the PFBTBr layer. The significant increase in efficiency and easy utilization indicate that this interfacial material has promising and practical application prospects.

Phosphine-free synthesis of heavy Co2+- and Fe2+-doped Cu2SnSe3 nanocrystals by virtue of alkylthiol-assistant Se powder dissolution

We demonstrate a phosphine-free method to synthesize heavy Co2+- and Fe2+-doped Cu2SnSe3 nanocrystals (NCs) by virtue of alkylthiol-assistant Se powder dissolution in organic solvents. The as-synthesized NCs exhibit a promising increase in photocurrent under AM1.5 illumination. Since the current method is simple and convenient it holds promise for facilitating the progress in photovoltaic devices from Cu-based NCs.

Oxadiazole containing poly(p-phenylenevinylene)s: synthesis and characterization

A series of poly(p-phenylenevinylene) based polymers (MEH-OXD-PPVs) functionalized with Y-shaped double 1,3,4-oxadiazole-containing side chains were synthesized through a modified Gilch reaction. They are all soluble in common organic solvents such as chloroform, tetrahydronfuran and 1,1,2,2-tetrachloroethane. The chemical structures of MEH-OXD-PPVs were determined by 1H NMR, GPC and elemental analysis. Thermogravimetric analysis shows that they have good thermal stability with the decomposition temperature ranging from 312 °C to 326 °C. The absorption and fluorescence emission maxima of the polymers exhibit an appreciable blue-shift with the increase of oxadiazole-containing moieties. Electrochemical investigation shows that the HOMO energy levels of the polymers vary regularly with the change of content of oxadiazole-containing moieties. Additionally, by introducing more OXD-PV unit during copolymerization, the PL quantum efficiencies of the polymers are significantly enhanced compared to that of MEH-PPV. The successful manipulation of optical and electronic properties of the MEH-OXD-PPVs indicates an effective concept for developing PPV-based functional materials with tunable optoelectronic properties by changing the amount of electron-withdrawing oxadiazole-containing moieties.

Synthesis and photovoltaic properties of non-fullerene solution processable small molecule acceptors

Two non-fullerene small molecules, BT-C6 and BT-C12, based on the vinylene-linked benzothiadiazole-thiophene(BT) moiety flanked with 2-(3,5,5-trimethylcyclohex-2-en-1-ylidene)malononitrile have been synthesized and characterized by solution/thin film UV-Vis absorption, photoluminescence(PL), and cyclic voltammetry(CV) measurements. The two molecules show intense absorption bands in a wide range from 300 nm to 700 nm and low optical bandgaps for BT-C6(1.60 eV) and for BT-C12(1.67 eV). The lowest unoccupied molecular orbital(LUMO) levels of both the molecules are relatively higher than that of [6,6]-phenyl C61 butyric acid methyl ester(PCBM), promising high open circuit voltage(Voc) for photovoltaic application. Bulk heterojunction(BHJ) solar cells with poly(3-hexylthiophene) (P3HT) as the electron donor and the two molecules as the acceptors were fabricated. Under 100 mW/cm2 AM 1.5 G illumination, the devices based on P3HT:BT-C6(1:1, mass ratio) show a power conversion efficiency(PCE) of 0.67%, a short-circuit current(Jsc) of 1.63 mA/cm2, an open circuit voltage(Voc) of 0.74 V, and a fill factor(FF) of 0.56.

Chloride treatment for highly efficient aqueous-processed CdTe nanocrystal-based hybrid solar cells

This work presents the influence of chloride treatment on the photovoltaic performance, microstructure, charge carrier dynamics, and surface chemical composition of aqueous-processed CdTe nanocrystal (NC)-based hybrid solar cells (HSCs). By applying CdCl2 treatment on the CdTe films through a spin-coating method, the power conversion efficiency (PCE) of the HSCs is largely improved from 4.49% to 6.01%. We show that the main role of chloride treatment is to promote the grain growth of the CdTe NCs, which leads to an increase in charge carrier lifetime. It is also demonstrated that CdCl2 treatment can prevent the generation of detrimental surface oxides and improve the wettability of the CdTe films.