Structure and performance analysis of the inorganic CsSnI3-based perovskite thin-film transistors used in the study:
(a) Bottom-gate/top-contact thin-film transistors
(b) Hole mobility and current ratio according to Csl/SnI2 molar ratios
(c) Hole mobility and current according to Pb substitution ratios in Csl-rich (x=1.25) ratio
(d) Thin-film transistor performance with Csl-rich (x=1.25) ratio and 10% Pb substitution ratio
(e) Output curve
(f) Performance of 100 transistors on 10 different samples fabricated with the optimized ratio.

A Pohang University of Science and Technology (POSTECH) research team has improved the performance of a p-type semiconductor 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 with n-type semiconductors. Compared to the 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 p-type semiconductors 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: caesium tin triiodide (CsSnI3), to develop the p-type perovskite semiconductor and fabricated the high-performance transistor based on this. The transistor exhibits high hole mobility of 50cm2V-1s-1 and more and an on/off current ratio of more than 108. This is the highest recorded 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. Since this method is not only convenient but also cost-effective, it can lead to the commercialization of perovskite devices in the future.

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