Black phosphorus: ambient degradation and strategies for protection

Elemental 2D black phosphorus (BP) is a highly anisotropic versatile material capable of exhibiting wide ranging electronic characteristics ranging from semi-metallic to semiconducting. Its thickness dependent tunable energy gap makes it an exciting prospect for deployment in a variety of applications. The main hurdle limiting diverse applications incorporating BP is its ambient instability. BP degrades rapidly under room conditions, affecting its structure and properties. In this report, we cover the recent progress that has occurred towards protecting BP from ambient degradation. We review the major developments in effectively countering the problem and compare their relative degrees of success. This is provided in the context of the mechanisms governing the atmospheric instability of this material. A targeted focus is kept on the various causes of degradation of BP in atmospheric conditions and the protection strategies that have been implemented so far.