Modifications to novel non-fullerene small molecule acceptor in organic thin film

… for solar cells demonstrates improved power conversion efficiency.

Scientists from the Imperial College London, Monash University, CSIRO, and King Abdullah University of Science and Technology have reported an organic thin film for solar cells with a non-fullerene small molecule acceptor that achieved a power conversion efficiency of just over 13 per cent.

By replacing phenylalkyl side chains in indacenodithieno[3,2-b]thiophene-based non-fullerene acceptor (ITIC) with simple linear chains to form C8-ITIC, they improved the photovoltaic performance of the material.

C8-ITIC was blended with a fluorinated analog of the donor polymer PBDB-T to form bulk-heterojunction thin films.

The research was recently published in Advanced Materials.

Dr Xuechen Jiao of McNeill Research Group at Monash University carried out grazing incidence wide angle X-ray scattering (GIWAXS) measurements at the Australian Synchrotron to gain morphological information on pure and blended thin films.

“By changing the chemical structure of the organic compound, a promising boost in efficiency was successfully achieved in an already high-performing organic solar cells” said Jiao.

>Read more on the Australian Synchrotron website


Ubiquitous formation of type-I and type-II bulk Dirac cones

… and topological surface states from a single orbital manifold in transition-metal dichalcogenides

Transition-metal dichalcogenides (TMDs) are renowned for their rich and varied properties. They range from metals and superconductorsto strongly spin-orbit-coupled semiconductors and charge-density-wave systems with their single-layer variants one of the most prominent current examples of two-dimensional materials beyond graphene.Their varied ground states largely depend on the transition metal d-electron-derived electronic states, on which the vast majority of attention has been concentrated to date.

>Read more on the Elettra website.

Image: Chalcogen-derived topological ladder in PdTe2.(a) Orbitally-resolved bulk electronic structure of PdTe2, indicating dominantly chalcogen-derived orbital character for the states in the vicinity of the Fermi level. (b) The measured out-of-plane dispersion together with the calculated band structure. Measured (c) and calculated (d) in-plane dispersion. (e,f) Spin-resolved energy distribution curves along the lines shown in (c).

Maximal Rashba-like spin splitting via kinetic-energy-coupled inversion-symmetry breaking

Research collaboration led by Professor Philip King from University of St. Andrews, and comprising the researchers from Max Planck Institute for Chemical Physics of Solids in Dresden, Institute for Theoretical Physics of the University of Heidelberg and researchers from I05 beamline at Diamond Light Source and APE beamline at Elettra, described a new route to maximise the spin-splitting of surface states.
The electronic properties of surfaces are often different from those of the bulk. In particular, the intrinsically broken symmetries of the surface compared with the bulk of the material allow for appearance of the new electronic surface states. For the systems in which spin-orbit interaction is strong, a non-negligible separation of these states according to their spin takes place. The spin splitting of surface- or interface-localized two-dimensional electron gases is characterized by a locking of the electron spin perpendicular to its momentum.

Read more on the Elettra website.

(a) Bulk and surface Fermi surfaces of PtCoO2 measured by ARPES; (b) Expected spin texture of the surface states; (c) Spin-resolved ARPES measurements of an in-plane spin polarization (〈Sy〉) of the Fermi surface for the cut along kx.

Highly Crystalline C8-BTBT Thin-Film Transistors by Lateral Homo-Epitaxial Growth on Printed Templates

The latest generation of organic semiconductors display excellent characteristics, with charge mobilities surpassing those of amorphous silicon thin film transistors (TFTs) that are commonly used in today’s flat panel displays. The integration of organic TFTs (OTFTs) into real applications requires high performance and low spread of the electrical characteristics. As transport properties are greatly influenced by the microstructure of the organic layer, single crystalline films offer the greatest potential for high-performance OTFTs.

Read more on the PSI website.

Image: Schematic illustration of lateral homo-epitaxial growth in which well-ordered zone-cast material provides a template for further deposited molecules.