Inorganic semiconducting nanostructures-based printed photodetectors

Optoelectronic devices, such as photodetectors (PDs), are needed in many applications including high-speed optical communications, robotics, healthcare, and biomimetic visual systems, which require detection and interaction using light. As a result, a wide variety of PDs on planar substrates have been reported using various light sensitive materials and traditional micro-/nano-fabrication technologies. In recent years, considerable efforts have been devoted to developing PDs with flexible form factors and using eco-friendly materials and approaches. These efforts have resulted in exploration of degradable materials and printed electronics as a resource-efficient route for manufacturing and to contain end-of-life issues. This paper reviews such new advances, particularly focusing on flexible PDs based on inorganic (e.g., crystalline silicon, compound semiconductors, metal oxides, etc.) semiconductor nanostructures [e.g., Nanowires (NWs), Nanoribbons (NRs), etc.]. The advantages and disadvantages of various bottom-up and top-down methods explored to realize the nanostructures and the wet (solution-processable) and dry printing and assembly methods to print the nanostructures on flexible substrates, are discussed along with their suitability for various applications. This discussion is supported by a comparative analysis of printed PDs in terms of key performance metrics such as responsivity, detectivity, ILight/IDark ratio, response speed, and external quantum efficiency. This comprehensive discussion is expected to benefit researchers and practitioners from academia and industry interested in the field of printed and flexible PDs.