Small molecule tandem organic photovoltaic cells incorporating an α-NPD optical spacer layer

We report an improvement in power conversion efficiency in a small molecule tandem organic photovoltaic (OPV) device by the optimisation of current balancing of the sub-cells using an optical spacer layer. A co-deposited layer of N,N’-bis(1-naphthyl)-N,N′-diphenyl-1,1’-biphenyl-4,4’-diamine (α-NPD) and molybdenum oxide was used as the optical spacer layer and provided a highly transparent and conductive layer. Optical simulations showed the addition of the optical spacer in a boron subphthalocyanine (SubPc)/C60 based tandem OPV device increased the SubPc absorption in the front sub-cell and resulted in current balancing through the device. Fabricated tandem OPV devices showed similar trends, with the power conversion efficiency increasing from 2.3% to 4.2% with the addition of an optimised optical spacer thickness. External quantum efficiency and total absorption efficiency measurements back up the optical model data which attribute the increased performance to improved SubPc absorption in the front sub-cell, balancing the photocurrents of the two sub-cells

On the Communication of Scientific Results: The Full-Metadata Format

In this paper, we introduce a scientific format for text-based data files, which facilitates storing and communicating tabular data sets. The so-called Full-Metadata Format builds on the widely used INI-standard and is based on four principles: readable self-documentation, flexible structure, fail-safe compatibility, and searchability. As a consequence, all metadata required to interpret the tabular data are stored in the same file, allowing for the automated generation of publication-ready tables and graphs and the semantic searchability of data file collections. The Full-Metadata Format is introduced on the basis of three comprehensive examples. The complete format and syntax is given in the appendix

Orbital redistribution in molecular nanostructures mediated by metal-organic bonds

Dicyanovinyl-quinquethiophene (DCV5T-Me) is a prototype conjugated oligomer for highly efficient organic solar cells. This class of oligothiophenes are built up by an electron-rich donor (D) backbone and terminal electron-deficient acceptor (A) moieties. Here, we investigated its structural and electronic properties when it is adsorbed on a Au(111) surface using low temperature scanning tunneling microscopy/spectroscopy (STM/STS) and atomic force microscopy (AFM). We find that DCV5T-Me self-assembles in extended chains, stabilized by intercalated Au atoms. The effect of metal-ligand hybridization with Au adatoms causes an energetic downshift of the DCV5T-Me lowest unoccupied molecular orbital (LUMO) with respect to the uncoordinated molecules on the surface. The asymmetric coordination of a gold atom to only one molecular end group leads to an asymmetric localization of the LUMO and LUMO+1 states at opposite sides. Using model density functional theory (DFT) calculations, we explain such orbital reshaping as a consequence of linear combinations of the original LUMO and LUMO+1 orbitals, mixed by the attachment of a bridging Au adatom. Our study shows that the alignment of molecular orbitals and their distribution within individual molecules can be modified by contacting them to metal atoms in specific sites

High Photoelectric Conversion Efficiency of Metal Phthalocyanine/Fullerene Heterojunction Photovoltaic Device

This paper introduces the fundamental physical characteristics of organic photovoltaic (OPV) devices. Photoelectric conversion efficiency is crucial to the evaluation of quality in OPV devices, and enhancing efficiency has been spurring on researchers to seek alternatives to this problem. In this paper, we focus on organic photovoltaic (OPV) devices and review several approaches to enhance the energy conversion efficiency of small molecular heterojunction OPV devices based on an optimal metal-phthalocyanine/fullerene (C60) planar heterojunction thin film structure. For the sake of discussion, these mechanisms have been divided into electrical and optical sections: (1) Electrical: Modification on electrodes or active regions to benefit carrier injection, charge transport and exciton dissociation; (2) Optical: Optional architectures or infilling to promote photon confinement and enhance absorption

The calcium looping cycle for CO2 capture from power generation, cement manufacture and hydrogen production

Calcium looping is a CO2 capture scheme using solid CaO-based sorbents to remove CO2 from flue gases, e.g., from a power plant, producing a concentrated stream of CO2 (∼95%) suitable for storage. The scheme exploits the reversible gas-solid reaction between CO2 and CaO(s) to form CaCO3(s). Calcium looping has a number of advantages compared to closer-to-market capture schemes, including: the use of circulating fluidised bed reactors-a mature technology at large scale; sorbent derived from cheap, abundant and environmentally benign limestone and dolomite precursors; and the relatively small efficiency penalty that it imposes on the power/industrial process (i.e., estimated at 6-8 percentage points, compared to 9.5-12.5 from amine-based post-combustion capture). A further advantage is the synergy with cement manufacture, which potentially allows for decarbonisation of both cement manufacture and power production. In addition, a number of advanced applications offer the potential for significant cost reductions in the production of hydrogen from fossil fuels coupled with CO2 capture. The range of applications of calcium looping are discussed here, including the progress made towards demonstrating this technology as a viable post-combustion capture technology using small-pilot scale rigs, and the early progress towards a 2MW scale demonstrator. © 2010 The Institution of Chemical Engineers

Biochemische Grundlagen der Wechselwirkungen von Barbituraten mit Alkohol Arbeitsbericht

SIGLETechnische Informationsbibliothek Hannover: D.Dt.F./AC 1000 (14,33) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Small-molecule solar cells—status and perspectives

In this paper we focus on the current status of organic solar cells based on small molecules. Since their discovery, much progress has been made, and the main steps are highlighted that led to the current state-of-the-art devices. However, organic solar cells still need to be improved further, and the main strategies for improving the power conversion efficiency, namely raising the open circuit voltage Voc and increasing the short circuit current density Jsc, are discussed. In theory, power conversion efficiencies of around 15% should be possible with a single heterojunction; for higher efficiencies, stacked solar cell concepts have to be employed