Photovoltaic semiconductors are capable of converting light into electricity. They are the principal components of solar cells that provide renewable energy from sunlight. These semiconductors tend to fail in a brittle manner, limiting their general use to small-scale applications. New evidence shows though that the mechanical behavior of photovoltaic semiconductors is sensitive to sunlight, exhibiting the potential of relative malleability under illumination. The mechanisms underlying such a light-mechanical coupling effect remain elusive. In this project, we and our experimental collaborators explore the photomechanical behavior of photovoltaic semiconductors using a multiscale modeling and experimental framework. We will characterize the influence of photoinduced electron-hole excitation on the dislocation and twining mechanics in cadmium telluride, a prototype photovoltaic semiconductor. On the sub-atomic scale, advanced quantum mechanics simulations will be performed to determine the influence of electron-hole pairs on the energy and force barriers of dislocation and twin nucleation, as well as dislocation mobility. On the atomic scale, we will develop a machine learning force field and apply this force field to explore the carrier concentration-dependent mechanisms of the dislocation-dislocation and dislocation-twin interactions. This work will result in a new physical picture of the deformation mechanism of photovoltaic semiconductors under light illumination, and provide a comprehensive understanding of light-mechanical coupling effects in general photovoltaic materials.