Effect of the structural features of polycrystalline semiconductor films on the formation of anomalous photovoltage: I. Phenomenon mechanism

A model for a polycrystalline semiconductor corresponding to its real structure is proposed. On the basis of this model, a mechanism for anomalous photovoltaic effects (the initiation of an anomalous photovoltage, its dependence on illumination angle, and anomalous photomagnetic effect) is developed. It is assumed that potential barriers introducing inhomogeneity into the spatial distribution of photocarriers arise due to the capture of majority charge carriers at surface states of the crystallite boundaries. The effect is heavily dependent on the barrier height: if the band bending at the crystallite boundaries is depleting, the effect is determined by the spatial separation of the majority photocarriers by the barrier; otherwise, (the inversion band bending) the effect is formed due to the separation of minority photocarriers. The basis for the mechanism is the anisotropy of light absorption in the polycrystal’s bulk (the depleting band bending) or the geometrical inhomogeneity of the films caused by oblique deposition during fabrication (the inversion band bending.) The cause of the anisotropic absorption of light is its reflection by crystallite boundaries.