High-mobility flexible/transparent p-type copper iodide thin-film transistors and complementary inverters

High-performance transparent and low-process-temperature p-type devices are essential for portable and 'invisible' electronics. In this work, high-performance p-channel copper iodide (CuI) thin-film transistors (TFTs) with a bottom-gate structure are achieved via replacing traditional SiO2 dielectric with Chitosan (CS, a kind of solid polymer electrolytes), with the threshold voltage down to -0.35 V, field-effect mobility (WFE) up to 60 cm2V- 1s- 1 and on/off current ratio (Ion/Ioff) beyond 103. The CuI films spin-coated on CS-dielectrics in the air with high humidity have smoother surface morphology, tinier grains, higher packing density and hence a higher WFE, in sharp contrast with the SiO2 case. In addition, the CuI films on CS-dielectrics demonstrate a work function - 0.1 eV lower than that on SiO2, which implies a smaller hole concentration and higher Ion/Ioff. And the low process temperature (<50 C) facilitates the achievement of flexible and transparent CuI TFTs with WFE and Ion/ Ioff comparable to those on rigid InSnO (ITO) glass. Furthermore, complementary inverters composed of p-type CuI and n-type ITO TFTs are demonstrated with clear inverting characteristics and voltage gain of over 20.

Automated summary

Achievement of high-performance p-channel copper iodide (CuI) thin-film transistors (TFTs) with a bottom-gate structure is demonstrated by replacing SiO2 dielectric with Chitosan (CS), resulting in a threshold voltage of -0.35 V, a field-effect mobility (WFE) up to 60 cm2V- 1s- 1, and an on/off current ratio (Ion/Ioff) beyond 103. CuI films on CS-dielectrics exhibit a smoother surface morphology, tinier grains, higher packing density, and a lower work function compared to those on SiO2, leading to enhanced performance. Low process temperature (<50 C) enables the realization of flexible and transparent CuI TFTs with comparable performance to those on rigid ITO glass. Moreover, complementary inverters composed of p-type CuI and n-type ITO TFTs exhibit clear inverting characteristics and voltage gain of over 20.