Researchers make a breakthrough in solar material

Using laser spectroscopy in a photophysics experiment, Clemson University researchers have broken new ground that could result in faster and cheaper energy to power electronics.

This new approach, using solution-processed perovskite, is intended to revolutionize a variety of everyday objects such as solar cells, LEDs, photodetectors for smartphones and computer chips. Solution-processed perovskite is the next generation of materials for solar panels on roofs, X-ray detectors for medical diagnosis and LEDs for lighting in daily life.

The research team included several graduate students and one undergraduate student led by Jianbo Gao, group leader of the Ultrafast Photophysics of Quantum Devices (UPQD) group in the College of Science’s Department of Physics and Astronomy.

The collaborative research was published in the journal with great impact on 12 March Nature communication. The article is entitled “In-situ Observation of Trapped Carriers in Organic Metal Halide Perovskite Films with Ultra-Fast Temporal and Ultra-High Energy Resolutions.”

The principal investigator was Gao, who is an assistant professor of condica physics. The co-authors included graduate students Kanishka Kobbekaduwa (first author) and Pan Adhikari of the UPQD group, as well as undergraduate Lawrence Coleman, a senior in the physics department.

Other Clemson writers were Apparao Rao, the RA Bowen professor of physics, and Exian Liu, a visiting student from China working under Gao.

“Perovskite materials are designed for optical applications such as solar cells and LEDs,” said Kobbekaduwa, a graduate student and first author of the research article. “This is important because it is much easier to synthesize compared to current silicon-based solar cells. This can be done by processing solutions – while having to use different methods in silicon that are more expensive and time-consuming.”

The aim of the research is to make materials that can be manufactured more efficiently, cheaper and more easily.

The unique method used by Gao’s team – with ultra-fast photocurrent spectroscopy – allowed a much higher time resolution than most methods to define the physics of the trapped carriers. Here the effort is measured in picoseconds, which is one trillionth of a second.

“We make devices that use this (perovskite) material and we use a laser to shine light on it and generate the electrons in the material,” Kobbekaduwa said. “And then, by using an external electric field, we generate a photocurrent. By measuring the photocurrent, we can actually tell people the characteristics of this material. In our case, we defined the trapped conditions, which defects in the material is what will affect. the stream we get. ‘

Once the physics is defined, researchers can identify the flaws – which ultimately cause inefficiency in the material. When the defects are reduced or passivated, it can lead to increased efficiency, which is critical for solar cells and other devices.

As materials are created through solution processes such as spin coating or inkjet printing, defects are more likely to occur. These low temperature processes are cheaper than ultra-high temperature methods which result in a pure material. But the compromise is more defective in the material. Finding a balance between the two techniques can mean higher and more efficient devices at lower costs.

The substrate samples were tested by firing a laser at the material to determine how the signal propagated through it. The use of a laser to illuminate the samples and collect the current made the work possible and distinguished it from other experiments that did not use an electric field.

“By analyzing the current, we can see how the electrons move and how they come out of a defect,” said Adhikari of the UPQD group. “This is only possible because we involve ultra – fast timescale and in-situ devices under an electric field. Once the electron falls into the defect, those experimenting with other techniques cannot take it out. But we can take it out because we have the electric “Electrons have charge under the electric field and can move from one place to another. We are able to analyze the transport from one point to another within the material.”

The transport and the effect of material defects on it can affect the performance of the material and the devices in which it is used. It is all part of the important discoveries that students make under the guidance of their mentor, which creates wrinkles that will lead to the next big breakthrough.

“The students not only learn; they actually do the work,” Gao said. “I’m fortunate to have talented students who – if inspired by challenges and ideas – will become influential researchers. It’s all part of the important discoveries that students make under the guidance of their mentors, creating ripples that will lead to the “We are also very grateful for the strong collaboration with Shreetu Shrestha and Wanyi Nie, who are the best materials scientists at the Los Alamos National Laboratory.”