Mechanism of the bulk photovoltaic effect in ferroelectrics

The high-voltage bulk photovoltaic effect in ferroelectrics was theoretically and experimentally studied focusing on the nonlinear dielectric response. The steady current in the absence of applied voltage, called "photocurrent", is considered as a result of photocarriers and the asymmetric electromotive force induced by near-ultraviolet radiation. A model accounting for the generation of electric field acting as an effective dc field for the photocarriers was explained in terms of the photoinduced nonlinear polarization and the Lorentz field in dielectrics. Experimental results on electric photoconductivity, photocurrent and photovoltage of a PLZT ceramic were analyzed by using exponential functions based on the model. An adjustable parameter was introduced in relation to the incoherence of the illuminating light as an electromagnetic wave. It was found that the exponential functions by the present model can give better fitting to the experimental data than that by a linear function previously used.