Morphological and micro-structural interface characterization in multilayer inverted polymer-fullerene bulk heterojunction solar cells

Inverted polymer solar cells based on P3HT/PCBM bulk heterojunction were prepared on flexible polyethylene naphthalate (PEN) substrate. The effect of annealing of the PEN/ITO/ZnO multilayer and ZnO/P3HT:PCBM on the structural, morphological, photophysical and photovoltaic properties was investigated and scrutinized directly on the OPV devices using atom probe tomography (APT), scanning electron microscopy (SEM) and microfocus X-ray techniques. We carried out a 3D reconstruction of the interfaces of the multilayer containing PEN/ITO, ZnO/ITO and P3HT:PCBM/ZnO to address the interface micro-structure and its influence on the morphology of the photoactive film. The analyses show that the morphology of the interfaces is affected by the structure of each layer of the BHJ devices causing orientation of P3HT crystals with PCBM aggregates and ZnO, which in turn leads to a significant change of the charge transport across each layer and therefore photovoltaic performances

Investigation at the atomic scale of the Co spatial distribution in Zn(Co)O magnetic semiconductor oxide

International audienceA sputtered Zn 0.95 Co 0.05 O layer was chemically analyzed at the atomic scale in order to provide an accurate image of the distribution of Co atoms in the ZnO matrix. The investigation of the magnetic properties shows that the as-deposited Zn 0.95 Co 0.05 O is ferromagnetic at room temperature. Atom probe tomography reveals a homogeneous distribution of all chemical species in the layer and the absence of any Co clustering. This result proves that the ferromagnetic properties of this magnetic semiconductor cannot be attributed to a secondary phase or to metallic Co precipitates within the layer

Investigation at the atomic scale of the Co spatial distribution in Zn(Co)O magnetic semiconductor oxide

International audienceA sputtered Zn 0.95 Co 0.05 O layer was chemically analyzed at the atomic scale in order to provide an accurate image of the distribution of Co atoms in the ZnO matrix. The investigation of the magnetic properties shows that the as-deposited Zn 0.95 Co 0.05 O is ferromagnetic at room temperature. Atom probe tomography reveals a homogeneous distribution of all chemical species in the layer and the absence of any Co clustering. This result proves that the ferromagnetic properties of this magnetic semiconductor cannot be attributed to a secondary phase or to metallic Co precipitates within the layer

Boron distribution in the core of Si nanowire grown by chemical vapor deposition

The boron dopant distribution in Si nanowires grown by the Au-catalyzed chemical vapor deposition is characterized by laser-assisted atom probe tomography. A convenient and an effective method for performing the atom probe tomography of an individual nanowire is developed. Using this technique, we demonstrate that when Si nanowires are doped with boron at high silane partial pressure, the radial distribution of boron atoms is rather inhomogeneous. Much more boron atoms incorporate at the periphery than in the center, with the concentration increasing by an order of magnitude as the distance from the nanowire axis increases from zero to only 15 nm. A theoretical model is presented that is capable of describing the observed spatial inhomogeneity of boron dopant. We also consider different kinetic pathways of boron incorporation and discuss the values of diffusion length and diffusion coefficients obtained by fitting the experimental dat

Boron distribution in the core of Si nanowire grown by chemical vapor deposition

The boron dopant distribution in Si nanowires grown by the Au-catalyzed chemical vapor deposition is characterized by laser-assisted atom probe tomography. A convenient and an effective method for performing the atom probe tomography of an individual nanowire is developed. Using this technique, we demonstrate that when Si nanowires are doped with boron at high silane partial pressure, the radial distribution of boron atoms is rather inhomogeneous. Much more boron atoms incorporate at the periphery than in the center, with the concentration increasing by an order of magnitude as the distance from the nanowire axis increases from zero to only 15 nm. A theoretical model is presented that is capable of describing the observed spatial inhomogeneity of boron dopant. We also consider different kinetic pathways of boron incorporation and discuss the values of diffusion length and diffusion coefficients obtained by fitting the experimental dat