 <p class="lead" id="first">The printing press has contributed immensely to the advancement of humankind 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.</p><p>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 semiconductortransistor 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.</p><p>Perovskite-based transistors control the current by combining p-type semiconductors that exhibit hole mobilities with n-type semiconductors. Compared to n-type semiconductors that have been actively studied so far, fabricating high-performance p-type semiconductors has been a challenge.</p><p>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.</p><p>To overcome this issue, the researchers used the modified inorganic metal halidecaesium tin triiodide (CsSnI<sub>3</sub>) to develop the p-type perovskite semiconductor and fabricated the high-performance transistor based on this. This transistor exhibits high hole mobility of 50cm<sup>2</sup>V<sup>-1</sup>s<sup>-1 </sup>and higher and the current ratio of more than 10<sup>8</sup>, and recorded the highest performance among the perovskite semiconductor transistors that have been developed so far.</p><p>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.</p><p>"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.</p><p>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.</p>