Led by Yang Yang, the Carol and Lawrence E. Tannas Jr Professor of Engineering at the Henry Samueli School of Engineering and Applied Science, researchers at University of California, Los Angeles (UCLA) have developed a photodetector that uses thin coatings of solution-processed perovskite material — rather than silicon or other common materials — which could reduce manufacturing costs and improve the quality of medical and commercial light sensors, it is reckoned (‘Solution-processed hybrid perovskite photodetectors with high detectivity’ by Letian Dou et al, Nature Communications 5 p5404).
Perovskite is an organic-inorganic hybrid material with a crystal structure that is extraordinarily efficient for converting light into electricity. In recent years, the use of perovskite materials has led to rapid advances in the efficiency of solar cells, note the researchers.
The photodetector is made using a process that essentially coats layers of the device in a liquid form of perovskite at about 300 degrees F. The process does not require the energy-consuming high heat or powerful vacuum procedures used to develop existing commercial photodetectors, say the researchers.
The perovskite coating is about 300nm thick, while the silicon layer in common photodetectors is more than 330 times as thick (100 microns). As a result, the device efficiently and quickly transports signals with minimum loss. It also offers improved sensitivity under dim light.
“Our innovation is using the perovskite material on a photodetector, and then putting it in the proper structure so that the material can work most efficiently,” says paper co-author Ziruo Hong, a research engineer in Yang Yang's lab.
Researchers also inverted the typical design of a perovskite-based photovoltaic cell, altering the materials that interface directly with the perovskite layer to improve its performance, especially response speed.
Operating at room temperature, the photodetectors exhibit a large detectivity (the ability to detect weak signals) approaching 1014 Jones, a linear dynamic range over 100dB and a fast photoresponse with 3dB bandwidth up to 3MHz. The performance is significantly better than most organic, quantum dot and hybrid photodetectors reported so far, it is claimed, and is comparable, or even better than, traditional inorganic semiconductor-based photodetectors.
“This device has the potential to improve the efficiency and contrast in optical sensors used in various applications,” says principal investigator Yang Yang, a member of the California NanoSystems Institute. With appropriate device interface design, perovskite materials are promising candidates for low-cost, high-performance photodetectors, it is reckoned. “Production requires less energy and time than is currently needed to make photodetectors, and so promises to make manufacturing on the industrial scale very cost-efficient,” he concludes.
The research was supported by the US National Science Foundation and Air Force Office of Scientific Research.