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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.
“GIWAXS gave us information about how the donor and acceptor molecules crystallised and aggregated within the thin films, as well as the orientation of the crystallites with respect to the substrates” said Jiao.
The technique is highly useful in investigating crystal structures of a range of soft matter thin films of conductive polymers, such as organic solar cells and organic transistors.
“The intensity of beam a the Australian Synchrotron provides a super high flux, that means information can be acquired in about three seconds compared with conventional XRD which takes about an hour,” said Jiao.
“Changes in colour in two-dimensional GIWAX patterns represent changes in diffraction intensity which allow you to see how the unit cell changes.”
In an experiment to examine crystalisation and aggregation behaviour, GIWAXS was implemented on single component thin films, ITC, C8-ITC, PBDB-T and PFDB-T with and without thermal annealing at 160 C .
Blends of C8-ITIC with donor polymer PFBDB-T demonstrated the best power conversion efficiency.
The results suggested C8-CTIC molecules have a higher tendency to crystallise into ordered 3D structures.
Improved molecular packing in C8-ITIC compared to CTIC was thought to contribute to superior charge carrier transporting behaviors, thus improved performance.
The paper authors, led by Prof Martin Heeney at the Imperial College London, also reported a new technique to synthesise the non-fullerene acceptor.
Other techniques used in the investigation included UV-absorption spectroscopy, cyclic voltammetry. atomic force microscopy electroluminescence and theoretical calculations.
There is a great deal of interest in non-fullerene acceptors because of their extended light absorption and tunable energy levels.
A group from the Chinese Academy of Sciences led by Wenchao Zhou recently reported in the Journal of the American Chemical Society last year that a molecular optimisation of 13 per cent in a non-fullerene thin film, of PBDB-T-SF and IT-4F.
DOI: 10.1002/adma.201705209
Technique provides insights into historic maritime artefact linked to early exploration of Australia
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Recently an advanced X-ray imaging technique was used on a historic pewter plate linked to the early exploration of Australia by the Dutch in the 17th century.
X-ray fluorescence (XRF) has proven to be a highly useful analytical tool for the study of cultural objects, such as works of art and artefacts.
“The non-destructive analysis can provide information about how the objects were made, their composition and insight for conservation strategies,” said XRF beamline scientist Dr Daryl Howard.
“The fast detector on the instrument and its high sensitivity allows us to keep the exposure to radiation to a minimum, which is important for rare and valuable objects. “
In December last year, a small group from the Rijksmuseum in Amsterdam and the Queen Victoria Museum and Art Gallery (QVMAG) in Tasmania brought the Hartog Plate to the Synchrotron for scanning.
Metals conservator Tamar Davidowitz (above left) from the Rijksmuseum and conservator David Thurrowgood (above right)from QVMAG wanted more detailed information about the condition of the plate in order to best preserve it into the future.
“It is a highly fragile object made up of many different fragments with a complex history of attempted restoration,” explained Howard.
“The technique provides a distribution of the metals in the plate, which might be useful in understanding its history and the corrosion that occurred when it was exposed to the elements on an island in Shark Bay over 80 years.”
Thurrowgood used XRF at the Synchrotron on the de Vlamingh plate (held by the Western Australian Museum) which provided clues as to its origin. (See text at bottom)
A special support was designed to hold the plate in place for transport and scanning.
One of the unexpected findings from the Hartog scans was the discovery of the missing letter ‘p’ from the Dutch word for ship ‘schip’ on the pewter plate.
“There was a great deal of excitement about this finding this character as there was some consternation as to why the letter was missing,” said Howard.
Using XRF the investigators were able to capture the distribution of individual elements on the surface.
“There was a lot of lead which was probably due to the environmental exposure,” said Howard.
“We also found copper, bismuth, and germanium and among many elements in the pewter plate,” said Howard.
The Dutch seafarers used pewter dinner plates hammered flat and engraved with text to leave a record of their voyages.
The first section of the text on the Hartog plate was deeply engraved but the rest was only lightly scratched in double lines on the surface. Most of the lightly scratched text has largely disappeared.
However, the faded inscription is clearly visible in XRF.
“As nails were used to affix the plate to the post, we can determine what the nails were made of at the time,” said Howard.
Ms Davidovitz said that although the plate is not beautiful, it is an important historical artefact , that captures an amazing story.
The Hartog plate is held in the collection of the Rijksmuseum but was exhibited in Australia last year to coincide with the 400th anniversary of Hartog’s expedition.
Dutch expedition leader Dirk Hartog was aboard the Eendracht when it reached Shark Bay (Western Australia) in 1616. He nailed an inscribed ship’s plate to an oak post to commemorate their landing.
Almost a century in 1697 later the plate was recovered by another Dutch expedition led by Willem de Vlamingh. He also left his own plate with of a record of his voyage and copied the inscription from Hartog.
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Read how a team from the University of Wollongong School of Physics used the Imaging and Medical beamline to investigate a new technique that is a potential treatment for brain tumours. Elette Engels (pictured above), winner of the Australian institute of Physics Postgraduate Excellence medal is featured in an article that appeared on the University of Wollongong website. The team of researchers involved in the MRT research program on the AS IMBL beamline includes Prof. Michael Lerch, Dr Moeava Tehei, Dr Susanna Guatelli, Dr Marco Petasecca and Dist. Prof. Anatoly Rozenfeld from the Centre for Medical Radiation Physics, University of Wollongong as well as Dr Stephanie Corde, Deputy Director of Radiation Oncology Medical Physics at Prince of Wales Hospital, Sydney. Read more: http://stand.uow.edu.au/shining-light-brain-cancer/