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Kim et al. Soft Sci 2024;4:33 https://dx.doi.org/10.20517/ss.2024.28 Page 9 of 31

Figure 4. (A) Transfer characteristics of CuI-based TFT with various concentrations of Zn dopants [80] . Copyright 2020 The Authors.
2+
2+
3+
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2+
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Published by Springer Nature; (B) Transfer characteristics of CuI-based TFT with various dopants (Ga , Zn , Ni , Bi , Pb , and Sn )
at optimized concentrations [80] . Copyright 2020 The Authors. Published by Springer Nature; (C) Transfer curves of printed CuBr I (x =
x 1-x
0, 0.2, 0.4, 0.6, and 0.8)-based TFTs [81] . Copyright 2022 The Royal Society of Chemistry; (D) Atomic force microscopy images of CuI
surfaces on SiO /Si substrates (top layer) and CS films (bottom layer) [84] . Copyright 2022 Elsevier B.V.; (E) Schematics of the lattice
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structure of air-annealed and vacuum-annealed CuI [40] . Copyright 2022 American Chemical Society. CuI: Copper iodide; TFT: thin-film
transistor.
CuI, resulting in smaller orbital overlap [39,57,82] . By increasing the ratio of Br compared to I in CuBr I , the
x 1-x
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3
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on/off current ratio grew from 10 to 10 , but the field effect mobility decreased from 9.06 to 0.02 cm ·V ·s
[81]
[Figure 4C] . Another experiment about CuIBr-based TFT was reported in 2023 by Wei et al.; it
was fabricated by a solution process at 100 °C under ambient conduction. The TFT demonstrated a
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high mobility of up to 5 cm ·V ·s and an on/off current ratio of up to 10 at 6.7% Br .
[83]
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Recently, various strategies besides doping have been reported to improve the electrical properties of CuI-
based TFTs [40,84,85] . Using high-capacitance dielectrics with mobile ions, such as ionic liquid, ion-gel, and
solid electrolyte, is effective in reducing operation voltage and high current for low mobility-based TFT
devices [86,87] . However, when calculating field-effect mobility with the device having high capacitance
dielectrics with mobile ions, careful examination of mobility calculation is necessary. As reported by Liang
et al., ultrahigh-apparent mobility over ten times could be observed with synchronous ion motion in the
dielectric layer . Wu et al. reported CuI-based TFT constructed on a chitosan (CS) dielectric layer. The
[88]
electrode and substrate were ITO and poly(ethylene terephthalate) (PET), respectively, for flexible TFT
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devices. This TFT demonstrated a high mobility of 65 cm ·V ·s and an on/off current ratio of 10 . CS has a
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