Donor-acceptor polymer-fullerene-based bulk heterojunction (BHJ) photovoltaic cells have many advantages; specifi cally, they can be fabricated in large-areas with simple solution methods involving a low-cost roll-to-roll manufacturing process. [1][2][3][4][5][6][7] The active layer in BHJ solar cells provides charge generation, separation, transport, and collection. During these steps, sweep-out of photo-generated carriers competes with charge recombination within the BHJ due to low carrier mobility. [8][9][10] Blocking the recombination is a key method of increasing device efficiency. [ 11 ] Therefore, we need to decrease the thickness of the active layer of BHJ fi lm and maximize its absorption capability to reduce the likelihood of recombination and thereby improve the effi ciency of the device.Metallic silver (Ag) nanoparticles (NPs) can be effective in thin fi lm solar cells because of their localized surface plasmon resonance, which can increase the light absorption capability of an active layer within a range of wavelengths. Thus, the addition of metal NPs into a BHJ active layer can potentially enhance the absorption and increase the photo-generation of mobile carriers. Several groups have recently reported that, when combined, polymer and metal NPs improve light absorption and cell effi ciency. [12][13][14][15] To ensure that metal NPs have positive effects in organic photovoltaic devices (OPVs), we must diminish the possibility of transferring nonradiative energy, which quenches excitons in the BHJ active layer. [ 12 , 15 ] Because of this concern, most researchers add metal NPs to the interface of the indium tin oxide (ITO) anode and the BHJ active layer; alternatively, they embed the metal NPs in a poly(3,4-ethylene dioxythiophene:poly(styrene sulfonate) (PEDOT:PSS) hole transporting interlayer to induce plasmon excitation within the thin BHJ fi lm. [ 12 , 16 , 17 ] However, Kim and Carroll directly added Ag or Au NPs to a BHJ polymer and confi rmed that the cell effi ciency was enhanced by the improved electrical conductivity. [ 13 ] The simple method of directly mixing metal NPs in an active layer is attractive because it enhances the overall performance of the cell. Specifi cally, this method can reduce the device resistance; [ 13 ] furthermore, the incident light can be refl ected and scattered by the embedded metal NPs while passing through the active layer, thereby increasing the optical path length of the incident light.Our study demonstrates several positive effects that arise from the addition of Ag NPs with controlled diameter size in BHJ photovoltaic cells fabricated with poly[N-9"-hepta-decanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole) (PCDTBT)/ [6,6]-phenyl C 70 butyric acid methyl-ester (PC 70 BM). Using effective, easily processable solution chemistry of a polyol process, we can synthesize Ag particles with wellcontrolled sizes and well-defi ned shapes. Specifi cally, we produced particles with diameters of 30 nm, 40 nm, and 60 nm. These Ag NPs have differe...

Graphene electronic circuits are prepared on paper substrates by using graphene nanoplates and applied to foldable paper-based electronics. The graphene circuits show a small change in conductance under various folding angles and maintain an electronic path on paper substrates after repetition of folding and unfolding. Foldable paper-based applications with graphene circuits exhibit excellent folding stability.

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The photocatalytic splitting of water into hydrogen and oxygen using solar light is a potentially clean and renewable source for hydrogen fuel. Titanium oxide nanotubes coated with tungsten oxide were prepared to harvest more solar light for the first time and characterized their water splitting efficiency. The tungsten trioxide coatings significantly enhanced the visible spectrum absorption of the titanium dioxide nanotube array, as well as their solar-spectrum induced photocurrents. For the sample, upon white light illumination at 150mW∕cm2, hydrogen gas generated at the overall conversion efficiency of 0.87%.

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Graphene-based carbon nanostructures with nanometer dimensions have been of great interest due to the existence of a bandgap. So far, well-ordered edge structure and uniformly synthesized graphene quantum dots (GQDs) with a hexagonal single-crystalline structure have not been directly observed owing to the limited precision of current synthesis approaches. Herein, we report on a novel approach not just for the synthesis of the size-controlled single-crystalline GQDs with hexagonal shape but also for a new discovery on constructing 2D and 3D graphene single crystal structures from d-glucose via catalytic solution chemistry. With size-controlled single-crystalline GQDs, we elucidated the crucial role of edge states on luminescence from the correlation between their crystalline size and exciton lifetime. Furthermore, blue-emissive single-crystalline GQDs were used as an emitter on light-emitting diodes and exhibit stable deep-blue emission regardless of the voltage and doping level.

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