Amorphous copper iodide: a p-type semiconductor for solution processed p-channel thin-film transistors and inverters

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 1; no. 2; pp. 7815 - 7821
• Main Authors: Lee, Han Ju, Lee, Seonjeong, Lee, Keun Hyung, Hong, Kihyon
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 26.05.2022
• Subjects: Amorphous materials; Amorphous semiconductors; Copper; High temperature; Low temperature; P-type semiconductors; Polycrystals; Semiconductor devices; Semiconductor materials; Semiconductors; Spin coating; Thin film transistors; Transistors
• DOI: 10.1039/d2tc00410k
• ISSN: 2050-7526

Until now, inorganic p-channel thin-film transistors (TFTs) have shown relatively low performance in terms of mobility, ON-current level, and on/off ratio compared to their n-channel counterparts. For inorganic p-channel TFTs, high-temperature annealed single- or poly-crystalline materials such as CuO, SnO, or 2D dichalcogenides have been the typical materials of choice. Development of amorphous semiconductor materials can provide a wide range of promising semiconductors for the TFT industry owing to their unique advantages, such as large area applicability, high device-to-device uniformity, and low temperature processing; however, the poor TFT performance using the conventional amorphous p-type semiconductors limits the use of materials in practical applications. In the present work, we demonstrate the 1st high-performance solution-processed p-channel TFT using an amorphous copper iodide (a-CuI) semiconductor, which outperforms its polycrystalline counterpart. Amorphous CuI films were formed by spin coating of precursor solutions based on co-solvents. By using a-CuI semiconductors as the channel layer, electrolyte-gated p-channel TFTs were fabricated with a vertical device structure. Measurement of the TFT characteristics reveals that the amorphous CuI channel layer leads to better device performance than devices with a polycrystalline CuI. The optimized vertical TFTs showed high current densities above 1000 mA cm −2 , ON/OFF current ratios of > 10 4 , and large normalized transconductances of about 6 S m −1 , which are the highest among solution-processed vertical TFTs. These results pave the way for application of amorphous p-type inorganics in high-performance complementary circuits and represent a breakthrough for p-type semiconductor materials. Amorphous p-type copper iodide (a-CuI) semiconductor and corresponding p-channel vertical TFTs are demonstrated. The a-CuI-TFTs exhibit excellent device performance, high current density of 1400 mA cm −2 and normalized transconductance of 6.46 S m −1 .