Phosphorene is a new 2D material that has recently attracted much attention owing to its fascinating electrical, optical, thermal, and chemical properties. Here, we report on high-quality exfoliation of black phosphorus nanosheets, with controllable size produced in large quantities by liquid phase exfoliation using N-methyl-2-pyrrolidone (NMP) as a solvent under ambient conditions. The as-synthesized few layers show a great potential for solar energy conversion based on the optical results shown in this work.