Layered black phosphorus (BP), a promising 2D material, tends to oxidize under ambient conditions. While such defective BP is typically considered undesirable, defect engineering has in fact been exploited in contemporary materials to create new behaviors and functionalities. In this spirit, new opportunities arising from intrinsic defect states in BP, particularly through harnessing unique photoresponse characteristics, and demonstrating three distinct optoelectronic applications are demonstrated. First, the ability to distinguish between UV-A and UV-B radiations using a single material that has tremendous implications for skin health management is shown. Second, the same device is utilized to show an optically stimulated mimicry of synaptic behavior opening new possibilities in neuromorphic computing. Third, it is shown that serially connected devices can be used to perform digital logic operations using light. The underpinning photoresponse is further translated on flexible substrates, highlighting the viability of the technology for mechanically conformable and wearable systems. This demonstration paves the way toward utilizing the unexplored potential offered by defect engineering of 2D materials for applications spanning across a broad range of disciplines.

Gallium nitride (GaN) technology has matured and commercialised for optoelectronic devices in the ultraviolet (UV) spectrum over the last few decades. Simultaneously, atomically thin materials with unique features have emerged as contenders for device miniaturization. However, the lack of successful techniques to produce ultra‐thin GaN prevents access to these new predicted properties. Here, this important gap is addressed by printing millimeter‐large ultra‐thin GaN nanosheets (NS) (≈1.4 nm) using a simple two‐step process that simultaneously introduces nitrogen point defects. This extends the photoelectrical spectral response from UV (280 nm) to near infrared (NIR) (1080 nm). The GaN‐based photodetectors display excellent figures of merit, having a responsivity (2.72 × 104 A W−1) up to four orders of magnitude higher than the commercial photodetectors at room temperature, despite being 102–103 times thinner. The photodetectors exhibit fast switching, with rise and decay time in the range of microseconds. The state‐of‐the‐art device performance originates from the ultra‐thin nature of GaN NS coupled with nitrogen point vacancies in the synthesis process. This work presents the opportunity to significantly expand the reach of GaN semiconductor technology and may lead to applications in high‐performance miniaturized imaging systems, spectroscopy, communication, and integrated optoelectronic circuits.

In article number 1901991, Taimur Ahmed, Sumeet Walia, and co‐workers exploit the defect engineering in layered black phosphorus to showcase new opportunities for optoelectronics. A wavelength‐selective unique photoresponse is reported. Optoelectronics‐enabled logic operations and optogenetics‐inspired neuromorphic computation are demonstrated.