Probing the Mg2Si/Si(111) heterojunction for photovoltaic applications

n-Mg2Si/p-Si heterojunction solar cell with a 1.4 mu m thick unintentionally doped (n = 3 x 10(17) cm(-3)) silicide epitaxial layer on p-Si(1 1 1) (p = 5 x 10(14) cm(-3)) was grown by low temperature (250 degrees C) molecular beam epitaxy. Heterojunction demonstrated clear rectification and zero bias photoresponse in the (400-1400) nm wavelength range at room temperature. Under AM 1.5 illumination, an open-circuit voltage of 0.21 V, a shortcircuit current density of 3.3 mA/cm(2), fill factor of 0.36 were obtained while the conversion efficiency reached 0.24%, which is the pioneering demonstration of Mg2Si-based solar cell operation. Combined minority-carrier lifetime, Raman and AFM mapping together with TEM and XRD data revealed that carrier dynamics and photovoltaic performance are limited by the presence of non-epitaxial Mg2Si grains in the upper silicide film layer. However, minority-carrier lifetime up to 7.3 mu s for Mg2Si demonstrates its great potential as absorbing material for Si-based solar cells.