Research progress on two-dimensional indium selenide crystals and optoelectronic devices

Two-dimensional (2D) materials, with unique electronic properties, superior optoelectronic properties, and dangling-bond-free surfaces, have attracted significant attention and experienced rapid development both in fundamental science and for practical applications. Amid the plethora of 2D materials, indium selenide (InSe) has emerged as a promising candidate for future high-mobility optoelectronic devices. Nobel Prize laureate Andre Geim even describes it as "the 'golden middle' between silicon and graphene". Over the past decade, remarkable findings and progress have been made in the fabrication of 2D InSe crystals and their application in devices, motivating us to delve deeply into these forefront developments. In this review, the physical properties such as the crystalline structure, band structure, and photoluminescence characteristics are discussed first. Then, the advancements in terms of synthesis techniques, characteristics and synthesis schemes in the fabrication of 2D InSe are summarized. Subsequently, the mechanisms of optimized strategies and recent progress in field effect transistors (FETs) as well as photodetectors based on this material are summarized, also highlighting the promising applications of 2D InSe in sensors and memory. Finally, an outlook, challenges and potential future research directions in the fabrication of 2D InSe and its devices are presented, such as large-scale fabrication without defect to integrate more devices, a variety of physical and chemical properties are regulated by doping or modification to broaden applications, improving the contact interface between the 2D materials and each layer of the stacking hetero interface to enhance the performance of devices, and designing multifunctional devices for future advanced optoelectronic devices as well as sensors, flexible, and wearable/portable electronic devices.2D InSe, a novel semiconductor with unique and excellent performance. It is pivotal for designing multifunctional devices for future optoelectronics, sensors, and flexible electronics, marking a significant advancement in materials science.