Improving Air-Stability and Performance of Bulk Heterojunction Polymer Solar Cells Using Solvent Engineered Hole Selective Interlayer.

In bulk heterojunction polymer solar cells (BHJ-PSCs), poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS) is the most commonly used hole selective interlayer (HSIL). However, its acidity, hygroscopic nature, and the use of indium tin oxide (ITO) etching can degrade the overall photovoltaic performance and the air-stability of BHJ-PSCs. Solvent engineering is considered as a facile approach to overcome these issues. In this work, we engineered the HSIL using ethanol (ET) treated PEDOT:PSS to simultaneously enhance the photovoltaic performance properties and air-stability of the fabricated devices. We systematically investigated the influence of ET on the microstructural, morphological, interfacial characteristics of modified HSIL and photovoltaic characteristics of BHJ-PSCs. Compared with the BHJ-PSC with pristine PEDOT:PSS, a significant enhancement of power conversion efficiency (~17%) was witnessed for the BHJ-PSC with PEDOT:PSS-ET (v/v, 1:0.5). Consequently, the BHJ-PSC with PEDOT:PSS-ET (v/v, 1:0.5) as HSIL exhibited remarkably improved air-stability.

Improving Photovoltaic Properties of P3HT:IC60BA through the Incorporation of Small Molecules.

We investigated the role of a functional solid additive, 2,3-dihydroxypyridine (DHP), in influencing the optoelectronic, morphological, structural and photovoltaic properties of bulk-heterojunction-based polymer solar cells (BHJ PSCs) fabricated using poly(3-hexylthiophene): indene-C60 bisadduct (P3HT:IC60BA) photoactive medium. A dramatic increase in the power conversion efficiency (~20%) was witnessed for the BHJ PSCs treated with DHP compared to the pristine devices. A plausible explanation describing the alignment of pyridine moieties of DHP with the indene side groups of IC60BA is presented with a view to improving the performance of the BHJ PSCs via improved crystalline order and hydrophobicity changes.

Direct electrochemistry of cytochrome c immobilized on titanium nitride/multi-walled carbon nanotube composite for amperometric nitrite biosensor.

In this report, titanium nitride (TiN) nanoparticles decorated multi-walled carbon nanotube (MWCNTs) nanocomposite is fabricated via a two-step process. These two steps involve the decoration of titanium dioxide nanoparticles onto the MWCNTs surface and a subsequent thermal nitridation. Transmission electron microscopy shows that TiN nanoparticles with a mean diameter of ≤ 20 nm are homogeneously dispersed onto the MWCNTs surface. Direct electrochemistry and electrocatalysis of cytochrome c immobilized on the MWCNTs-TiN composite modified on a glassy carbon electrode for nitrite sensing are investigated. Under optimum conditions, the current response is linear to its concentration from 1 µM to 2000 µM with a sensitivity of 121.5 µA µM(-1)cm(-2) and a low detection limit of 0.0014 µM. The proposed electrode shows good reproducibility and long-term stability. The applicability of the as-prepared biosensor is validated by the successful detection of nitrite in tap and sea water samples.

Incorporation of Gold Nanodots Into Poly(3,4-ethylenedioxythiophene):Poly(styrene sulfonate) for an Efficient Anode Interfacial Layer for Improved Plasmonic Organic Photovoltaics.

In this paper, we demonstrate a simple strategy for the incorporation of gold nanodots (GNDs) into poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) ( PEDOT: PSS) films, towards fabrication of an efficient anode interfacial layer in order to improve the performance of bulk heterojunction (BHJ) solar cells that use a blend of poly(3-hexyl thiophene) and [6,6]-phenyl-C71 butyric acid methyl ester as the organic active layer. We synthesized citrate-stabilized GNDs, with sizes in the range of -20-30 nm, by initially blending them into PEDOT: PSS by aqueous dispersion. The influence of GNDs in the PEDOT: PSS layer on the photovoltaic characteristics of BHJ solar cells was investigated. Our results show that the improved performance is due to the enhanced conductivity and increased interfacial contact area between the PEDOT: PSS and organic active layer, owing to the inclusion of GNDs into the PEDOT: PSS. The BHJ solar cell included with GNDs (0.02 wt%) into PEDOT: PSS exhibited a power conversion efficiency (PCE) of 2.92% with an open circuit voltage of 0.61 V, fill factor of 50%, and a short-circuit current density of 9.51 mA/cm2, whereas the pristine device exhibited a PCE of 2.52%.

Enhanced Performance of Light-Emitting Diodes by Surface Ligand Modification on Quantum Dots.

The electrical characteristics of quantum dots (QDs) can vary depending on the surface modulation, which can change the luminance and efficiency of electroluminescent devices. Thus, understanding surface ligand is essential in improving the performance of QDs-based light-emitting diodes (LEDs). We analyzed the performance of QDs-based LEDs with respect to the QD surface volume. On the QD surfaces, the 1.1 nm-long tryoctylphosphine oxide (TOPO) ligand with three neck-type structure was replaced with a 1.7 nm-long oleic acid (OA) ligand with a one neck-type structure to evaluate the dependence of the LED properties on the ligand length. With all other conditions being identical, the luminance and efficiency of the QDs-based LEDs with an OA ligand were approximately 1,000 cd/m2 greater and 1.5 times higher, respectively, than those of the QDs-based LEDs with a TOPO ligand. These results show that if the physical length of the surface ligand is relatively long, decreasing the surface area would result in increased injection of electrons and holes into the QDs, increasing the luminance and efficiency.

Solution Processable CdSe/ZnS Quantum Dots Light-Emitting Diodes Using ZnO Nanocrystal as Electron Transport Layer.

In this paper, we propose interface engineering between cadmium selenide/zinc sulfide (CdSe/ZnS) quantum dots (QDs) as the emissive layer (EML) and ZnO nanocrystals (NCs) as the electron transport layer (ETL) for reducing the potential barrier in QDs based light-emitting diode (QLED). The n-type ZnO NCs were effective in confining charge to the QDs EML because of their wide band gap. The ZnO NCs were synthesized using a modified sol-gel process and were applied as the ETL in QLED. For comparison, a standard QLED with Tris(8-hydroxyquinolinato)aluminium as the ETL was also fabricated. The standard QLED was shown to have a luminance of 11,240 cd/m2 and current efficiency of 2.3 cd/A. However, QLED with ZnO NCs showed a higher luminance of 28,760 cd/m2 and current efficiency of 4.9 cd/A than the reference structure, and so has more efficient charge transport. Thus, QLED with ZnO NCs not only simplified the process, but also enhanced the luminance and current efficiency by factor of two.

New Heterojunction Titanium Dioxide Nanowire as Photocatalyst.

Graphene and metal nanoparticles were incorporated into titanium dioxide nanowires. The heterojunction generated in the titanium dioxide nanowires was beneficially utilized for photocatalytic degradation of Rhodamine-B.

Efficient visible-light-driven photocatalytic degradation of nitrophenol by using graphene-encapsulated TiO2 nanowires.

In this work, a new hybrid nanocatalyst, namely titanium dioxide (TiO2) composite nanowires, encapsulated with graphene (G) and palladium nanoparticles (Pd NPs) (designated as G-Pd@TiO2-CNWs), was prepared. In preparing the nanowires, a combination of electrospinning and hydrothermal approaches was employed. The visible-light-driven photocatalytic performance of G-Pd@TiO2-CNWs was investigated using the reduction of 4-nitrophenol (4-NP) as a model reaction. The results showed that G-Pd@TiO2-CNWs converted nearly 100% of 4-NP under visible light irradiation. The reaction kinetics of the photocatalytic reduction of 4-NP was studied by UV-vis spectrophotometry and the apparent rate constant was determined and compared with those for other supported TiO2 catalysts. Furthermore, the spent G-Pd@TiO2-CNWs could be recovered by simple centrifugation and reused. The work is expected to shed new light on the development of G-incorporated hybrid nanostructures for harvesting light energy and on the development of new photocatalysts for the removal of environmental pollutants.

Facile electrodeposition of flower like gold nanostructures on a conducting polymer support.

Herein, we report an attractive, simple and templateless synthetic method for the formation of anisotropic gold nanostructures. Gold 'mesoflowers' consisting of arrays of nanoplatelets were synthesized by electrochemical gold deposition on/off conditions onto a conducting poly(diphenylamine) (PDPA) support matrix. A possible forming mechanism of anisotropic gold nanostructures is presented. The electronic and electrochemical properties of gold nanoflower decorated PDPA in an assembled diode configuration were evaluated.

Nanodiamond based sponges with entrapped enzyme: a novel electrochemical probe for hydrogen peroxide.

A "modular approach" has been demonstrated for the preparation of nanodiamond (ND) based sponges (NS) with entrapped enzyme (horseradish peroxidase, HRP) (ND-NS(HRP)) and utilization as an electrochemical probe for detection of hydrogen peroxide (H2O2). ND-NS comprises ND, porous poly(aniline)-poly(2-acrylamido 2-methyl propane sulfonic acid) (PANI-PAMPSA) network and entrapped HRP. Field emission scanning electron microscope image of ND-NS(HRP) reveals sponge like suprastructure comprising interconnected nanospheres with numerous openings/pinholes/cavities. The entrapped HRP in ND-NS exhibits effective direct electron transfer with an electron transfer rate constant of 1.85 s(-1). ND-NS(HRP) exhibited excellent bioelectrocatalytic reduction of hydrogen peroxide (H2O2) with a wide linear concentration range (1-45 mM), quick response (5s), high sensitivity (129.6 µAM(-1)) and low detection limit 59 µM (S/N=3).