Qunliang Song

Graphene quantum-dot-doped polypyrrole counter electrode for high-performance dye-sensitized solar cells.

Herein graphene quantum dot (GQD), a graphene material with lateral dimension less than 100 nm, is explored to dope PPy on F-doped tin oxide glass as an efficient counter electrode for high-performance dye-sensitized solar cells (DSSCs). The GQDs-doped PPy film has a porous structure in comparison to the densely structured plain PPy, and displays higher catalytic current density and lower charge transfer resistance than the latter toward I3(-)/I(-) redox reaction. The highest power conversion efficiency (5.27%) for DSSCs is achieved with PPy doped with10% GQDs, which is comparable to that of Pt counter electrode-based DSSCs. This work provides an inexpensive alternative to replace platinum for DSSCs.

Electrical transport and photovoltaic effects of core–shell CuO/C60 nanowire heterostructure

An organic/inorganic hybrid heterostructure consisting of p-type CuO nanowire core and n-type C(60) shell was fabricated and its electrical transport properties were studied for the first time. It was found that the devices with contacts on shell-shell show an ohmic behavior but the devices with contacts on core-shell forms a single p-n junction and display a rectifying behavior. Logarithmic current-voltage curves at various temperatures show that the tunneling transport plays a critical role in the electrical transport. Photovoltaic effects were observed in the core-shell contacted CuO/C(60) junctions under illumination. This work demonstrates that an inorganic/organic coaxial nanowire can provide potential in nanoelectronic devices and could further stack high density hybrid nanowires array as a renewable power source.

Single-crystalline Bi2S3 nanowire network film and its optical switches

A single-crystalline bismuth sulfide (Bi(2)S(3)) nanowire network film at a centimeter scale is fabricated by the facile hydrothermal method. The Bi(2)S(3) film is easily tape-transferred onto a soft plastic substrate, and is further used to fabricate optical switches by screen-printing an Agxa0electrode array on its top. Our studies demonstrate that the Bi(2)S(3) nanowire network has a pronounced increase in conductance upon exposure to visible light, and possesses a very fast response time of about 2xa0ms. This work provides a simple and economic method to fabricate a high performance optical switch array and could offer great potential for a low cost, mass-manufacturing process.

Electrochemically polymerized nanostructured poly(3.4-ethylenedioxythiophene)-poly(styrenesulfonate) buffer layer for a high performance polymer solar cell

An electrochemically polymerized uniform column-like poly(3.4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:Pss) nanostructure synthesized on indium tin oxide substrate has been used as the buffer layer to construct a polymer bulk heterojunction solar cell, demonstrating 50% higher power conversion efficiency (from 2.56 to 3.86%) than that of using the spin-coated PEDOT:Pss as the buffer layer. The enhanced device performance is ascribed to the improved carrier transport from the highly dense, uniform column-like PEDOT: Pss nanostructure, which penetrates into the polymer blend film to improve the connection of the active layer with the anode while providing a large conducting area for charge transport. This approach is compatible with the state-of-the-art bulk heterojunction solar cells, thus offering a high throughput, low cost manufacturing process for a high performance device.

Investigation of the behaviour of electronic resistive switching memory based on MoSe2-doped ultralong Se microwires

MoSe2-doped ultralong Se microwires of length/diameter ratio in the order of ∼240 are synthesized by hydrothermal method. An electronic resistive switching memory (ERSM) device using a single MoSe2-doped ultralong Se microwire is attained. The ERSM exhibits stable resistance ratio of ∼102 for 5000u2009s, highly stable performance during 500 stressing cycles, and excellent immunity to the frequency of the driving voltage. By investigating the dynamic processes of trap filling, de-trapping, and free-charge migration, trap-controlled space-charge-limited current mechanism is found to dominate the observed ERSM behaviour.

Magnetoelectroluminescence in tris (8-hydroxyquinolato) aluminum-based organic light-emitting diodes doped with fluorescent dyes

The influences of fluorescent dye doping on the magnetoelectroluminescence in tris (8-hydroxyquinolato) aluminum (Alq3)-based organic light-emitting diodes have been investigated systematically by varying the dopant concentrations and its energy band gap. Our results show that the decrease in electroluminescence intensity at high magnetic field, which survives only at low temperatures for pure Alq3-based devices, persists in dye-doped devices even at room temperature. This is explained here as the result of magnetic field dependent triplet-triplet annihilation process, in which the triplet excitons trapped on the dye molecules play the most important role.

Spark plasma sintering-fabricated one-dimensional nanoscale “crystalline-amorphous” carbon heterojunction

One-dimensional (1D) nanoscale “crystalline-amorphous” carbon heterojunction is fabricated by post-treatment of an amorphous carbon nanofiber in a spark plasma sintering (SPS) system. It is proposed that the unique SPS process is responsible for the heterojunction formation. Studies of the electrical transport property show that the nanoscale heterojunction exhibits a typical rectification behavior. The heterojunctions may have broad potential applications in nanoelectronics and optoelectronics and the SPS technique could be a distinctive approach to construct 1D functional nanomaterials with high throughput.

Positive and negative components of magnetoconductance in hole transport limited organic light-emitting diodes

Two kinds of devices using N,N′-Di(naphthalen-1-yl)-N,N′-diphenyl-benzidine (NPB) and dye-doped NPB as emitting layer were fabricated to study their magnetoconductance (MC) response. The MC of the NPB devices contains a positive low-field (0 40u2002mT) component at low temperatures. Similar MC is presented in the dye-doped NPB devices even at room temperature. Magnetoelectroluminescence results and energy-level diagram indicate that long lifetime triplet excitons and excessive holes are in these devices. All these observations suggest that triplet exciton-hole reaction is responsible for the negative MC while positive MC is assigned to hyperfine mixing of electron-hole pairs.

Efficient perovskite solar cell fabricated in ambient air using one-step spin-coating

One-step spin coating is a simple method which has been widely used in fabricating perovskite solar cells. However, this method was vastly demonstrated in glove box wherein the influence of moisture is negligible. Thus the use of one-step spin-coating in ambient air has not been comprehensively investigated. In this work, we employ one-step spin-coating method to coat perovskite films in ambient air (with humidity above 50%), and then the perovskite films are annealed in vacuum or air. Experimental results show that by using vacuum annealing, a power conversion efficiency of 12.98% is attained, and this is 45% higher than that attained by air annealing method. This improvement is mainly attributed to the fast solvent evaporation process in vacuum during annealing, which induces high supersaturation that leads to higher coverage of perovskite film.

Hydrogen-peroxide-modified egg albumen for transparent and flexible resistive switching memory

Egg albumen is modified by hydrogen peroxide with concentrations of 5%, 10%, 15% and 30% at room temperature. Compared with devices without modification, a memory cell of Ag/10% H2O2-egg albumen/indium tin oxide exhibits obviously enhanced resistive switching memory behavior with a resistance ratio of 104, self-healing switching endurance for 900 cycles and a prolonged retention time for a 104 s @ 200 mV reading voltage after being bent 103 times. The breakage of massive protein chains occurs followed by the recombination of new protein chain networks due to the oxidation of amidogen and the synthesis of disulfide during the hydrogen peroxide modifying egg albumen. Ions such as Fe3+, Na+, K+, which are surrounded by protein chains, are exposed to the outside of protein chains to generate a series of traps during the egg albumen degeneration process. According to the fitting results of the double logarithm I-V curves and the current-sensing atomic force microscopy (CS-AFM) images of the ON and OFF states, the charge transfer from one trap center to its neighboring trap center is responsible for the resistive switching memory phenomena. The results of our work indicate that hydrogen- peroxide-modified egg albumen could open up a new avenue of biomaterial application in nanoelectronic systems.