Photoluminescence Spectroscopy At Low Temperatures

Researchers have improved a method for probing semiconducting crystals with light to detect defects and impurities. The omnidirectional photoluminescence spectroscopy set-up could help improve the fabrication of materials for electric cars and solar cells. The technique can test materials at very low temperatures and can find even small amounts of defects and impurities.

The researchers demonstrated their approach using gallium nitride crystals. Gallium nitride is a semiconducting crystal that has been used in energy-saving light-emitting diodes (LEDs) since the 2000s. It has interesting optic and electronic properties, making it attractive for many applications, including power-switching devices in electric vehicles. But it can develop defects and impurities during its fabrication, which can affect performance. Currently available methods for testing these crystals are expensive or too invasive. The omnidirectional photoluminescence spectroscopy is a non-invasive technique that can solve this problem.

The team’s modification means the temperature change crucially happens only within the crystal and not within the sphere. They next plan to use the method for testing other materials, such as perovskites for use in highly efficient solar cells and boron nitride as an atomically thin two-dimensional material.

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