POSTECH: Simply Printing High-Performance Perovskite-based Transistors

The printing press has contributed immensely to the advancement of mankind by elevating politics, economy, and culture to higher grounds. Today, it goes beyond simply printing books or documents, and is expanding its influence to the realm of cutting-edge technology. Most notably, high-performance components in various smart devices have been successfully printed and have attracted much attention. And now, a technology to print perovskite-based devices – considered a challenge until now – has been proposed.

A POSTECH research team led by Professor Yong-Young Noh and Ph.D. candidates Ao Liu and Huihui Zhu (Department of Chemical Engineering), in collaboration with Professor Myung-Gil Kim (School of Advanced Materials Science and Engineering) of Sungkyunkwan University, has improved the performance of a p-type semiconductor*1 transistor using inorganic metal halide perovskite. One of the biggest advantages of the new technology is that it enables solution-processed perovskite transistors to be simply printed as semiconductor-like circuits.

Perovskite-based transistors control the current by combining p-type semiconductors that exhibit hole mobilities*2 with n-type semiconductors.*3 Compared to n-type semiconductors that have been actively studied so far, fabricating high-performance p-type semiconductors has been a challenge.

Many researchers have tried to utilize perovskite in the p-type semiconductor for its excellent electrical conductivity, but its poor electrical performance and reproducibility have hindered commercialization.

To overcome this issue, the researchers used the modified inorganic metal halide*4 caesium tin triiodide (CsSnI3) to develop the p-type perovskite semiconductor and fabricated the high-performance transistor based on this. This transistor exhibits high hole mobility of 50cm2V-1s-1 and higher and the current ratio*5 of more than 108, and recorded the highest performance among the perovskite semiconductor transistors that have been developed so far.

By making the material into a solution, the researchers succeeded in simply printing the p-type semiconductor transistor as if printing a document. This method is not only convenient but also cost-effective, which can lead to the commercialization of perovskite devices in the future.

“The newly developed semiconductor material and transistor can be widely applicable as logic circuits in high-end displays and in wearable electronic devices, and also be used in stacked electronic circuits and optoelectronic devices by stacking them vertically with silicon semiconductors,” explained Professor Yong-Young Noh on the significance of the study.

Published in Nature Electronics, a sister journal of the world-renowned scientific journal Nature, this study was conducted with the support from the Mid-Career Researcher Program, Creative Materials Discovery Program, Next-generation Intelligence-Type Semiconductor Development Program, and the Basic Research Lab Program of the National Research Foundation of Korea, and from Samsung Display Corporation.

1. P-type semiconductor
A semiconductor that generally has holes as charge carriers. A semiconductor in which the number of electron-carrying holes is much greater than the number of electrons.

2. Hole mobility
An empty space created when an electron is subtracted is called a hole. If an electron has a charge of -1, a hole is a charge carrier with a charge of +1.

3. N-type semiconductor
A semiconductor that generally has electrons as charge carriers. A semiconductor in which the number of electrons is much greater than the number of holes

4. Metal halide
a substance with a bond between a metal and a halogen

5. On/Off current ratio
The ratio between the maximum current when the transistor is operating (on state) and the minimum current when it is turned off (off state).