CdSe quantum dots have been encapped with aromatic ligands: a-toluenethiol, thiophenol, and p-hydroxythiophenol to enhance the photoluminescence (PL) quenching and photoelectric properties of the quantum dots. The aromatic ligand capped CdSe quantum dots are prepared through ligand exchange with trioctylphosphine oxide (TOPO) capped CdSe quantum dots. The XPS surface chemistry analysis and elemental analysis has confirmed the success of ligand exchange from TOPO to aromatic ligands. Both XRD and HRTEM-SAED studies indicate the crystalline structure of CdSe quantum dots not only remains but is also improved by the ligand exchange of TOPO with thiol molecules. Time resolved PL decay measurements indicate thiophenol and p-hydroxythiophenol ligands effectively quench the emission and have much shorter PL lifetimes than that of TOPO and that of a-toluenethiol. Thus, both thiophenol and p-hydroxythiophenol can act as an effective acceptor for photogenerated holes through aromatic p-electrons. Thiophenol also exhibits good charge transport behavior showing a 10-fold increase in short circuit current density (I sc ) as compared with TOPO in the photocurrent study of fabricated photovoltaic devices.

Einfach mal blau machen: Die Photolumineszenz in Suspensionen von Graphenoxid (GO) lässt sich von roter zu blauer Emission durchstimmen (siehe Bild), indem man die Anteile von sp2‐ und sp3‐C‐Atomen durch Reduktion der Oxidgruppen auf der Oberfläche schrittweise verändert. Eine Elektron‐Loch‐Rekombination aus zwei Typen angeregter Zustände kann die GO‐Lumineszenz bei unterschiedlichen Reduktionsgraden erklären.

Energy scavenging has become a fundamental part of ubiquitous sensor networks. Of all the scavenging technologies, solar has the highest power density available. However, the energy source is erratic. Integrating energy conversion and storage devices is a viable route to obtain self-powered electronic systems which have long-term maintenance-free operation. In this work, we demonstrate an integrated-power-sheet, consisting of a string of series connected organic photovoltaic cells (OPCs) and graphene supercapacitors on a single substrate, using graphene as a common platform. This results in lighter and more flexible power packs. Graphene is used in different forms and qualities for different functions. Chemical vapor deposition grown high quality graphene is used as a transparent conductor, while solution exfoliated graphene pastes are used as supercapacitor electrodes. Solution-based coating techniques are used to deposit the separate components onto a single substrate, making the process compatible with roll-to-roll manufacture. Eight series connected OPCs based on poly(3-hexylthiophene)(P3HT):phenyl-C61-butyric acid methyl ester (PC60 BM) bulk-heterojunction cells with aluminum electrodes, resulting in a ≈5 V open-circuit voltage, provide the energy harvesting capability. Supercapacitors based on graphene ink with ≈2.5 mF cm(-2) capacitance provide the energy storage capability. The integrated-power-sheet with photovoltaic (PV) energy harvesting and storage functions had a mass of 0.35 g plus the substrate.

Organic (P3HT/PCBM) solar cells are coated with ZnO nanowires as antireflection coatings and show up to 36% enhancement in efficiency. The improvement is ascribed to an effective refractive index which results in Fabry-Perot absorption bands which match the polymer band-gap. The effect is particularly pronounced at high light incidence angles. Simultaneously, the coating is used as a UV-barrier, demonstrating a 50% reduction in the rate of degradation of the polymers under accelerated lifetime testing. The coating also allows the surface of the solar cell to self-clean via two distinct routes. On one hand, photocatalytic degradation of organic material on ZnO is enhanced by the high surface area of the nanowires and quantified by dye degradation measurements. On the other, the surface of the nanowires can be functionalized to tune the water contact angle from superhydrophilic (16°) to superhydrophobic (152°), resulting in self-cleaning via the Lotus effect. The multifunctional ZnO nanowires are grown by a low cost, low temperature hydrothermal method, compatible with process limitations of organic solar cells.

Structural and optical properties of single crystal Zn 1−x Mg x O nanorods ͑0 Յ x Յ 0.17͒ are studied experimentally and theoretically. Structural analyses indicate that the nanorods grown on Si substrates are oriented in the c-axis direction and the nanorods possess the single-crystalline hexagonal structure with the Mg incorporated within the ZnO nanorods by means of substituting Zn. A blueshift of the near-band edge emission in the photoluminescence spectra by increasing Mg content is observed. Two distinct emission bands are found in the photoluminescence spectra; one is mainly attributed to the delocalized exciton recombination and the other is originating from localized excitons due to the incorporation of foreign impurity of Mg. Enhanced exciton localization with increasing Mg content in Zn 1−x Mg x O nanorods is mainly due to large ionic characters of Mg-O bonding. Structural stability, band structures, projected density of states, and charge distribution in various Zn 1−x Mg x O alloy compounds were further investigated by first-principles calculations. A good agreement between experimental and theoretical results is found.