A research team led by Professor Yong-Young Noh and Dr. Youjin Reo from the Department of Chemical Engineering at POSTECH (Pohang University of Science and Technology) has developed a groundbreaking technology poised to revolutionize next-generation displays and electronic devices. The project was a collaborative effort with Professors Ao Liu and Huihui Zhu from the University of Electronic Science and Technology of China (UESTC), and the findings were published in Nature Electronics on April 28th.
Every time we stream videos or play games on our smartphones, thousands of transistors operate tirelessly behind the scenes. These microscopic components function like traffic signals, regulating electric currents to display images and ensure smooth app operation. Transistors are typically categorized as n-type (electron transport) and p-type (hole transport), with n-type devices generally demonstrating superior performance. However, to achieve a high speed computing with a low power consumption, p-type transistors must also reach comparable efficiency.
To address this challenge, the research team focused on a novel p-type semiconducting material with a unique crystal structure: tin-based perovskites. This material has emerged as a promising candidate for high-performance p-type transistors. Traditionally, it has only been fabricated through a solution process—a technique akin to soaking ink into paper—which presents challenges in scalability and consistent quality.
In a significant breakthrough, the team successfully applied thermal evaporation, a process widely used across industries such as OLED TV and semiconductoring chips manufacturing, to produce high-quality caesium-tin-iodide (CsSnI3) semiconductor layers. This technique involves vaporizing materials at high temperatures to form thin films on substrates.
Furthermore, by adding a small amount of lead chloride (PbCl2), the researchers were able to improve the uniformity and crystallinity of the perovskite thin films. The resulting transistors exhibited outstanding performance, achieving a hole mobility of over 30 cm2/V·s and an on/off current ratio of 108 which are comparable to already commercialized n-type oxide semiconductors—indicating rapid signal processing and low power consumption during switching.
This innovation not only enhances device stability but also enables the fabrication of large-area device arrays, effectively overcoming two major limitations of previous solution-based methods. Importantly, the technology is compatible with existing manufacturing equipment used in OLED display production, presenting significant potential to reduce costs and streamline fabrication processes.
"This technology opens up exciting possibilities for the commercialization of ultra-thin, flexible, and high-resolution displays in smartphones, TVs, vertically stacked integrated circuits and even wearable electronics because low processing temperature below 300 ℃," said Professor Yong-Young Noh.
This research was supported by the National Research Foundation of Korea (NRF) under the Mid-Career Researcher Program, the National Semiconductor Laboratory Core Technology Development Project, and Samsung Display.
