Towards controlled dislocations

October 20, 2014

Crystallographic defects or irregularities (known as dislocations) are often found within crystalline materials. Two main types of dislocation exist: edge and screw type. However, dislocations found in real materials tend to be a mix of these two types, resulting in a complex atomic arrangement not found in bulk crystals. The study of these dislocations in semiconductors is probably as old as the science of semiconductors itself, and the technological importance of dislocations can hardly be overstated. From their roles in the way crystals form to their effects on a material's mechanical, thermal and opto-electronic properties, dislocation and defects govern many aspects of a material's behaviour. Therefore, it is of great scientific interest to identify and study these structures, and understand their impact on the properties of technologically important materials and devices, such as solar cells, photon detectors and similar semiconductor devices.

Despite the large amount of theoretical work in this field, experimental knowledge detailing the atomically resolved chemical structure of even the most basic dislocations has just begun to be accessible. A group of scientists from the United States has combined state-of-the-art atomic-resolution Z-contrast imaging and X-ray spectroscopy in a scanning transmission electron microscope (STEM) to analyse two low-elastic-energy stair-rod dislocations in the binary II-VI semiconductor CdTe. CdTe is commercially used in thin-film photovoltaics owing to its ideal electrical properties. The conversion efficiency of CdTe solar cells, which is critical for the industry, has only seen minor developments and improvements over the last 20 years despite intense research activity. Current laboratory records are still shy of the theoretical limits quoted as far back as 1961.

In the current issue of Acta Crystallographica Section A: Foundations and Advances, Klie and co-workers demonstrate how, with the use of atomic-resolution STEM images and specially tailored Burgers circuits, the structure of these dislocations can be identified [Paulauskas et al. (2014). Acta Cryst. A70; doi:10.1107/S2053273314019639]. The results may lead to the eventual improvement in the conversion efficiency of CdTe solar cells. The analysis presented by the authors can also be applied to study and predict similar structures in other zinc-blende and diamond materials. This study further demonstrates how the new generation of aberration-corrected electron microscopes can advance our understanding of seemingly basic crystal-structure defects.
-end-


International Union of Crystallography

Related Solar Cells Articles from Brightsurf:

Solar cells of the future
Organic solar cells are cheaper to produce and more flexible than their counterparts made of crystalline silicon, but do not offer the same level of efficiency or stability.

A blast of gas for better solar cells
Treating silicon with carbon dioxide gas in plasma processing brings simplicity and control to a key step for making solar cells.

Record efficiency for printed solar cells
A new study reports the highest efficiency ever recorded for full roll-to-roll printed perovskite solar cells.

Next gen solar cells perform better when there's a camera around
A literal ''trick of the light'' can detect imperfections in next-gen solar cells, boosting their efficiency to match that of existing silicon-based versions, researchers have found.

On the trail of organic solar cells' efficiency
Scientists at TU Dresden and Hasselt University in Belgium investigated the physical causes that limit the efficiency of novel solar cells based on organic molecular materials.

Exciting tweaks for organic solar cells
A molecular tweak has improved organic solar cell performance, bringing us closer to cheaper, efficient, and more easily manufactured photovoltaics.

For cheaper solar cells, thinner really is better
Researchers at MIT and at the National Renewable Energy Laboratory (NREL) have outlined a pathway to slashing costs further, this time by slimming down the silicon cells themselves.

Flexible thinking on silicon solar cells
Combining silicon with a highly elastic polymer backing produces solar cells that have record-breaking stretchability and high efficiency.

Perovskite solar cells get an upgrade
Rice University materials scientists find inorganic compounds quench defects in perovskite-based solar cells and expand their tolerance of light, humidity and heat.

Can solar technology kill cancer cells?
Michigan State University scientists have revealed a new way to detect and attack cancer cells using technology traditionally reserved for solar power.

Read More: Solar Cells News and Solar Cells Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.