Cathodoluminescence imaging on quartz in sandstone

Best microscopy techniques for studying CIGS thin-film solar cells

Posted by Delmic on Sep 23, 2019 2:48:00 PM

A copper indium gallium selenide (or CIGS), a direct bandgap semiconductor is being commonly used for solar cell production. Thin-film solar cells made with this structure have received a lot of attention from the photovoltaics community for exhibiting conversion efficiencies of almost up to 23%. 

Various microscopy techniques are commonly used to perform optoelectronic characterization of these highly relevant solar cell devices. These techniques include FIB-SEM investigations, for instance, which can help to investigate the high capability solar cells and do the material microstructure measurements. It is also quite common to use such techniques as electron backscatter diffraction, energy-dispersive X-ray spectrometry (EDX), electron-beam-induced current (EBIC). 

One extremely powerful technique for analysing Cu(In,Ga)Se2 layers in high-efficiency solar cells is cathodoluminescence (CL). It is particularly useful for observing the Ga/In gradient and how it influences the optoelectronic properties of Cu(In,Ga)Se2 layers. It is possible to use energy-dispersive X-ray spectrometry to observe local-band-gap energies, but cathodoluminescence can be a more efficient technique for direct access of these local optoelectronic quantities. 

Figure 1: SEM (a) and panchromatic CL images (b) acquired on the same identical area on a cross-section specimen prepared from a ZnO/CdS Cu(In,Ga)Se2/Mo/glass solar cell stack.

ZnO/CdS Cu(In,Ga)Se2/Mo/glass solar cell stack (Figure 1) was analysed with cathodoluminescence imaging at room temperature, and a CL spectrum was acquired in each pixel. While comparing the SEM and panchromatic CL images acquired on the same identical area it is possible to see that the CL intensity in neighbouring grains is different. These images also allow to conclude that the intensity is reduced at the grain boundaries due to enhanced nonradiative recombination. 

Moreover, peak shifts in the CL map reveal the distribution of the local band-gap energy/wavelength well. 

This experiment was performed by a research group from Helmholtz-Zentrum Berlin, which soon will host a workshop dedicated to studying photovoltaic materials with cathodoluminescence. The workshop will consist of several talks and hands-on sessions which will focus on the most relevant and advanced techniques for studying photovoltaic materials. The workshop is free and you can still register for it below.

Register for the workshop

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Best practice for studying plasmonic structures with microscopy

Posted by Delmic on Aug 8, 2019 2:03:39 PM

Plasmons have gained a lot of interest for their ability to strongly confine light to very small volumes, which makes the field of plasmonics so attractive. Various materials can be used in plasmonics, such as aluminium, gold, gallium, and others. One of the main advantages of plasmonic materials is their ability to enhance and direct emission, therefore, they can be successfully used for nanoantennas, sensing and local heating.

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Measuring time dynamics with time-resolved cathodoluminescence

Posted by Delmic on Jul 17, 2019 10:37:00 AM

Cathodoluminescence has established itself as a powerful technique for measuring and understanding various properties of light. In the previous blog posts, we explained how intensity mapping can be used to measure amplitude of the electromagnetic waves, hyperspectral CL for wavelength measurements, angle-resolved CL for wave vector, and polarimetry for polarization. These properties of light are not static, which means that there is time dynamics associated with light, which can also be studied. How? Keep reading!

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Polarization-filtered cathodoluminescence for studying nanostructured devices

Posted by Delmic on Jun 17, 2019 10:52:00 AM



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CL intensity mapping: ideal imaging technique for geological samples

Posted by Delmic on May 30, 2019 11:49:00 AM

One of the fastest and most straightforward techniques for understanding the composition and structure of geological samples is intensity mapping. What is it exactly? This imaging mode allows quickly obtaining cathodoluminescence contrast of the sample by acquiring CL intensity for every beam position. 

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The most modular cathodoluminescence detector: The SPARC

Posted by Delmic on May 15, 2019 1:30:00 PM



When adding the new equipment to the lab, it is important to consider a lot of various factors. One of such factors is how much experimental freedom the new system can offer. Not only it has to be configured specifically to cater your scientific needs, but also, ideally, it has to be modular in order to change as your experiments evolve. 

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What is Hyperspectral Cathodoluminescence?

Posted by Delmic on Apr 24, 2019 1:09:00 PM

For the past few weeks we have been focusing on possibilities of cathodoluminescence imaging of the SPARC CL detector. In this post we describe hyperspectral cathodoluminescence, which is a powerful tool for wavelength spectrum visualisation. 

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Spectrally and angular-resolved cathodoluminescence explained

Posted by Delmic on Mar 27, 2019 2:20:00 PM

What is spectrally and angular-resolved (also known as energy-momentum) CL?

In the last blog post we explained angle-resolved cathodoluminescence imaging, a technique which is used to acquire angular profiles and gain a better understanding of materials' optical properties. The imaging technique that we are focusing on this week combines information acquired with angle-resolved imaging and high-resolution spectroscopy. This technique is called Lens-scanning energy-momentum (LSEK) Imaging, or full Angle-Resolved Spectroscopy, and it allows collecting a full emission spectrum for each emission angle. This new imaging technique is now available with the SPARC system. Keep reading if you would like to understand how it works and what results can be achieved.

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What is Angle-Resolved Cathodoluminescence?

Posted by Delmic on Mar 15, 2019 1:05:00 PM

In our last blog post we presented all six cathodoluminescence imaging modes that can be used with our SPARC detector to analyse and observe samples. In this blog post we are going to focus on angle-resolved cathodoluminescence, a technique which allows to create angular profiles of the samples.

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How to study properties of rare-earth doped materials with cathodoluminescence

Posted by Delmic on Feb 20, 2019 3:09:00 PM

Rare-earth elements, also known as REE, are a group of elements, consisting of scandium, yttrium and 15 lanthanide elements. In the last decades there has been a significant growth in the number of devices that use rare-earth metals. They can be found in a wide range of technological areas and are commonly used in lighting and displays, CT scanners and electron microscopes, (fiber) lasers and amplifiers, anti-cancer agents, fluorescent markers, batteries, magnets and catalysists. Rare-earth elements are crucial for modern-day technology and it is important to study rare-earth doped materials at nanoscale to understand them better.

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Thoughts on the various applications, techniques, and complications to be discovered in the fascinating fields of both cathodoluminescence and correlative light and electron microscopy.

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