2D binary transition metal iodides: Advances in synthesis and device applications

A subclass of 2D metal halides referred here as binary transition metal iodide of a form MX 2 and MX 3 (M = transition metal X = iodide) possess electronic, optical and magnetic properties due to their layered structure. In this review, we emphasize the distinct characteristics of BTMIs—such as their tunable bandgaps, multifaceted magnetic behavior, and potential for heterostructure integration—that differentiate them from other 2D materials. This work also provides a detailed comparative analysis of synthesis techniques and device performances, thereby narrowing the scope of previous reviews and offering clear guidance for future research. We systematically examine synthesis methods—including exfoliation, solution-based techniques, and vapor deposition—and evaluate the performance of BTMIs in photodetectors, field-effect transistors, flexible devices, and magnetic applications. Finally, we discuss current challenges, limitations, and prospects for the future development of this promising class of 2D materials.