Jan D'Haen

Perovskite‐Based Hybrid Solar Cells Exceeding 10% Efficiency with High Reproducibility Using a Thin Film Sandwich Approach

Organometal halide perovskites have tremendous potential as light absorbers for photovoltaic applications. In this work we demonstrate hybrid solar cells based on the mixed perovskite CH3 NH3 PbI2 Cl in a thin film sandwich structure, with unprecedented reproducibility and generating efficiencies up to 10.8%. The successfulness of our approach is corroborated by the experimental electronic structure determination of this perovskite.

Copper sorption and accumulation by the extraradical mycelium of different Glomus spp. (arbuscular mycorrhizal fungi) isolated from the same polluted soil

The form and localisation of Cu accumulation in the extraradical mycelium (ERM) of three arbuscular mycorrhizal fungi (AMF), isolated from the same polluted soil contaminated with the Cu and Arsenate, was studied. There were differences in the capacity of the ERM of the three AMF to sorb and accumulate Cu. Glomus caledonium BEG133 had a significantly lower Cu-sorption capacity than Glomus mosseae BEG132 and Glomus claroideum BEG134 isolated from the polluted soil as well as an isolate of G. mosseae BEG25 from a non-polluted soil. This was directly related to the cation exchange capacity (CEC) of the ERM of these fungi. Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) linked to an energy dispersive X-ray spectrometer (EDAX) gave more detailed information, showing that the ERM of AMF from the polluted soil was able to accumulate Cu in the mucilaginous outer hyphal wall zone, cell wall and inside the hyphal cytoplasm. The EDAX spectra showed that the accumulated Cu was mainly associated with Fe in the mucilaginous outer hyphal wall zone and in the cell wall. Cu was associated with traces of arsenate inside the cytoplasm of the ERM of Glomus mosseae BEG132 but this was not visible inside the ERM of Glomus caledonium BEG133 or Glomus claroideum BEG134. This work suggests that the ERM of AMF is able to sorb and accumulate Cu, but different tolerance mechanisms exist between the three AMF isolated from the same polluted soil providing further evidence for functional diversity within populations of AMF in soils.

PEDOT/PSS: synthesis, characterization, properties and applications

AGFA Gevaert NV, R&D Mat, B-2640 Mortsel, Belgium. IMOMEC, B-3590 Diepenbeek, Belgium.Louwet, F, AGFA Gevaert NV, R&D Mat, Septestr 27, B-2640 Mortsel, Belgium.

A quantitative model for the evolution from random orientation to a unique texture in PVD thin film growth

Abstract The continuous evolution from a random crystalline orientation (near the substrate) towards a definite texture (near the outer surface), established in the previous paper for PVD TiN coatings, was modelled quantitatively. The tendency for the smallest possible surface energy was considered as the driving force for the texture evolution. The experimental trends observed in the texture evolution could be reproduced, using realistic parameters. From an analytical treatment simple expressions for crucial characteristics of the texture evolution could be obtained, as for instance for the typical time (or thickness) at which the system will switch from a random to a peaked distribution, and for the time dependence of the spread of the orientational distribution of the crystallites in the growing film.

Towards Efficient Hybrid Solar Cells Based on Fully Polymer Infiltrated ZnO Nanorod Arrays

L.B. and B.C. contributed equally to this work. The authors thank R. Rieke from Rieke Metals for useful suggestions. This work was financially supported by BOF, UHasselt, the Flemish Odysseus program, and the Interreg project Organext. A. H. is a postdoctoral research fellow of the Research Foundation-Flanders (FWO Vlaanderen).

Efficient formation, isolation and characterization of poly(3-alkylthiophene) nanofibres: probing order as a function of side-chain length

Efficient fibre formation for all regioregular poly(3-alkylthiophene)s (P3ATs) with alkyl chain lengths (A) between 3 and 9 carbon atoms has been accomplished in several solvents. It was observed that for the aliphatic and (chlorinated) aromatic hydrocarbon solvents used, the solvent refractive index offers some rationale to predict the feasibility of a solvent for fibre formation. The fibres were separated from remaining non-organised polymer by centrifugation. This enabled the characterisation of the isolated fibres in function of alkyl chain length (A) with TEM, AFM, XRD and UV-Vis spectroscopy. The fibres are 20 ± 5 nm wide and 0.5 to >4 µm long and mainly crystallize in the common type I crystal phase. The order within the fibres was probed with XRD, SAED, and UV-Vis and was found to strongly improve with increasing alkyl chain length in going from P33T to P35T, resulting in a longer conjugation length. For P35T to P39T the improvement in order is only marginal. Fibres from P37T were found to mainly crystallize in a crystal phase slightly different from type I that we refer to as type I′. This new crystal structure has a lattice constant a that is marginally shorter than that of phase I and a slightly longer lattice constant b of 4.0 A and thus in XRD can hardly be distinguished from phase I. It is furthermore characterized by a blue-shifted absorption band in UV-Vis spectroscopy. The type I′ fibres were converted into normal type I fibres in the solid state at 70 °C and in solution around 50 °C.

Modeling the temperature induced degradation kinetics of the short circuit current in organic bulk heterojunction solar cells

We acknowledge the institute for the promotion of science and technology in Flanders (IWT Vlaanderen) for funding via the IWT-SBO project Polyspec, the Fund for Scientific Research, Flanders (Belgium) (F.W.O.) in the framework of project G.0252.04 and the Special Research Fund (B.O.F.).

Separation of intra- and intergranular magnetotransport properties in nanocrystalline diamond films on the metallic side of the metal-insulator transition

A systematic study on the morphology and electronic properties of thin heavily boron-doped nanocrystalline diamond (NCD)films is presented. The films have nominally the same thickness ( 150nm) and are grown with a fixed B/C ratio (5000ppm) but with different C/H ratios (0.5-5%) in the gas phase. The morphology of the films is investigated by x-ray diffraction and atomic force microscopy measurements, which confirm that lower C/H ratios lead to a larger average grain size. Magnetotransport measurements reveal a decrease in resistivity and a large increase in mobility, approaching the values obtained for single-crystal diamond as the average grain size of the films increases. In all films, the temperature dependence of resistivity decreases with larger grains and the charge carrier density and mobility are thermally activated. It is possible

Aqueous Chemical Solution Deposition of Ferroelectric Thin Films

Thin films of various ferroelectric multimetal oxides such as (Bi 1 m x La x ) 4 Ti 3 O 12 (BLT), SrBi 2 Ta 2 O 9 (SBT) and PbZr 1 m x Ti x O 3 (PZT) have been prepared by an entirely aqueous chemical solution deposition (CSD) route. Two critical issues related with aqueous CSD have hereby been worked out: in spite of the high degree of hydrolysis of tetra- and pentavalent metal ions (Ti 4+ , Zr 4+ , Ta 5+ , ) we managed to prepare stable aqueous precursor solutions by chemical modification of these individual metals, avoiding phase segregation. Another problem related with aqueous CSD is the wetting of the substrate (both metallic and metal oxide) by the aqueous solution. The hydrophilicity of the substrates is optimized by a chemical treatment of the substrate surface. In this manner, the addition of wetting agents, hence possibly disturbing the gelation reactions, is avoided. In order to study the gelation, decomposition, crystalization and the morphology of the thin films, various characterization techniques ((cryo-)TEM, SEM, EDX, TGA-MS/FTIR, HT-DRIFT, HT-XRD, ) are used.

Convenient synthesis of ordered mesoporous silica at room temperature and quasi-neutral pH

A new synthesis procedure is presented to prepare P6m ordered mesoporous silica at room temperature and quasi-neutral pH in a buffered medium using a cheap silicon source.