We report that two rotated layers of blue phosphorene behave as a direct band gap
semiconductor. The optical spectrum shows absorption peaks in the visible region of the
spectrum and in addition the energy of these peaks can be tuned with the rotational angle.
These findings makes twisted bilayer blue phosphorene a strong candidate as a solar cell or
photodetection device. Our results are based on ab initio calculations of several rotated blue
phosphorene layers.