Electronic structures and optical properties induced by silicon twin boundaries: The first-principle calculation

•Defect states and optical absorption enhancement induced by twin boundaries in silicon are investigated theoretically.•Dielectric functions and absorption coefficients are derived.•Enhanced visible light absorption by the twinning configuration is demonstrated.•Twinning structures play an important role in silicon-based photovoltaic devices.

The defect states and optical absorption enhancement induced by twin boundaries in silicon are investigated by first-principle calculation. The defect states in the forbidden bands are identified and based on the established electronic structures, the dielectric functions and absorption coefficients are derived. An important result of our calculations is that visible light absorption by the twinning configuration is enhanced significantly, indicating that twinning structures possibly play an important role in silicon-based photovoltaic devices.