Composite materials can play a decisive role to reveal novel physical properties and enable to advance new generation technologies. Here, we discover that phototransistors based on the integration of two-dimensional graphene nanosheets (GNSs) and amorphous indium− gallium−zinc−oxide (a-IGZO) semiconductors exhibit a giant photo-to-dark current ratio and long-lasting persistent photoconductivity (PPC). Under the illumination of UV light (350 nm) at 50 mW/cm 2 , a photo-to-dark current ratio up to 2.0 × 10 7 was obtained, which is about 3 orders of magnitude higher than its pure a-IGZO device counterpart. Moreover, the GNSs/a-IGZO phototransistor possesses an enduring lifetime up to years for the recovery of the transfer characteristics after switching off the UV light. The giant and long-lasting PPC leads GNSs/a-IGZO to become an excellent conductor with conductivity much better than indium tin oxide. The observed unique features represent a semiconductor−conductor transition. In addition to next generation flat, flexible, and display, it can open up a wide variety of application, such as transparent electrodes for optoelectronic devices, optical memory, and light harvesting for energy storage. As an example, we demonstrated the operation of optical memory devices, which may lead to the novel application of holographic storage. Our results shown here therefore provide an outstanding new route for the future development of solution-processable semiconducting optoelectronic devices. D ue to the coupling among constituent materials, hybrid composites enable to possess exceptional properties and multifunctionality, which cannot be found in single component. As a result, their applications can be expanded to a wide range of fields. Recently, amorphous oxide semiconductor (AOS) have created a new area of electronics and optoelectronic devices. 1,2 Among the various AOS types, amorphous indium− gallium−zinc oxide (a-IGZO) thin-film transistors (TFTs) have been considered to be one of the most promising candidates for next-generation flat, flexible, and transparent display devices, mainly owing to their high electron mobility, optical transparency, chemical stability, and processing versatility. 3,4 Replacing TFTs made of hydrogenated amorphous silicon (aSi: H) with transparent a-IGZO TFTs can significantly boost the aperture ratio of pixels, reduce the power, and simplify device fabrication. 5,6 For system-on-panel (SoP) applications, IGZO-based nonvolatile memory (NVM) is required, and many research teams are actively pursuing related devices. 7−9 Besides, the IGZO-based TFTs have been utilized in phototransistors and photosensors due to their high sensitivity to light, mobility, and on/off ratio for integrated circuits. 10,11 With the additional terminal, light memory devices based on IGZO and AOS phototransistor can be realized with the special optical programming and electrical erasing processes. 12,13 To ensure the application in nonvolatile memories such as flash memory, a long retention time is one of the most imp...

Transparent and flexible thin film transistors (TFTs) with high performance based on solution processed graphene nanosheets (GNSs)-amorphous indium-gallium-zinc-oxide (a-IGZO) composites have been developed. A high electron mobility of 23.8 cm 2 V À1 s À1 has been achieved, which is about thirty times higher than those of the pristine a-IGZO TFTs (0.82 cm 2 V À1 s À1 ) and hydrogenated amorphous silicon (<1 cm 2 V À1 s À1 ). The on/off current ratio remains in a high order of 10 6 demonstrating the sustainability of the TFT devices. In addition, transparent GNSs-a-IGZO TFTs with a Ta 2 O 5 dielectric layer show superior resistance to mechanical bending with the variation of only 8% in mobility after 100 times of repeated cyclic bending compared with the degradation of more than 70% for the pristine a-IGZO device. Our results demonstrate that GNSs not only play an important role in forming a conducting network in the active matrix, but also enhance the mechanical bending stability of GNSsa-IGZO composites. It therefore paves a key step to develop large-scale applications for next-generation transparent and flexible electronics.

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