Improving transistor performance through perovskite-cation incorporation

The research team led by Professor Yong-Young Noh, Dr. Ao Liu, and Dr. Huihui Zhu from the Department of Chemical Engineering at Pohang University of Science and Technology (POSTECH) has developed world-class perovskite transistors through the utilization of three distinct perovskite cation processes. This collaborative research has recently been published in Nature Electronics on August 21, 2023.

In semiconductor technology, both n-type and p-type transistors are necessary for constructing electronic circuits. N-type semiconductors facilitate current flow through the movement of electrons, while p-type semiconductors allow current to pass through the movement of holes¹. Despite this need for both n-type and p-type semiconductors for electronic circuits, the development of efficient p-type semiconductors has been challenging due to the superior electron mobility of most semiconductor materials compared to hole mobility. This issue has been recognized as one of the top 10 challenges in technology by the nation.

Tin halide perovskites represent promising p-type semiconductors with impressive hole mobility, making them candidates for next-generation high-performance p-channel transistors. Perovskites, described by the chemical formula ABX₃, consist of two types of cations (A and B) and one anion (X). The research team has been developing high-performance p-type perovskite semiconductor materials by combining various compounds. In 2022, they developed transistors with the best performance at the time using a combination of cesium-tin-iodide (Cs-Sn-I) and reported their findings in Nature Electronics.

In this study, the team ingeniously employed a mixture of three cations -- formamidinium (FA), cesium (Cs) and phenethylammonium (PEA) -- in the A-site of perovskite (ABX₃) cations. While previous studies had used these cations separately, this study is the first to combine all three. As a result, the team succeeded in developing a high-quality p-type perovskite semiconductor layer with reduced defects.

Building upon this achievement, they implemented transistors with high hole mobility (70 cm²V^-1s^-1) and an on/off current ratio (10⁸), enabling faster computing with lower power consumption. These results represent the highest performance level of p-type perovskite transistors reported to date, nearly equivalent to commercially available low-temperature polysilicon transistors used in OLED drive circuits. The research team has once again succeeded in developing the world's best-performing transistors, surpassing their performance from the previous year.

Professor Noh remarked, "If the performance of low-temperature process p-type semiconductors improves to be comparable to n-type semiconductors, we can create electronic circuits with faster performance and greatly enhance data processing speeds. I hold hopes for this research to find widespread application in the electrical and electronic engineering arena, harnessing the potential of semiconductors and transistors."

This study received support from the BK21 FOUR Program for Education Program for Innovative Chemical Engineering Leaders of the National Research Foundation of Korea (NRF), the National Semiconductor Laboratory Program, and Samsung Display.