Resonant tunneling through defects in an insulator: Modeling and solar cell applications

In this paper, a model for electron tunneling through defects in an insulator is presented. The three-dimensional results for the electron transmission coefficient can be obtained by characterizing the tunneling process in terms of a defect density and capture cross section. Fitting the model parameters by comparison with the results of a full three-dimensional tunneling-through-defect simulation, this model can be used to calculate and predict the electron transmission for various spatial distributions of defects without performing the complex three-dimensional calculations. Energy selective contacts using the resonant tunneling for carrier extraction have been proposed as a means to achieve a higher efficiency in future generations of photovoltaic devices. Resonant tunneling through defects in an insulator, where the defects may be atoms or quantum dots, may provide a possible implementation for such energy selective contacts. With the present model, the influences of the tunneling effective mass, insulator thickness, and defect distribution on the electron transmission coefficient have been investigated. The results suggest that the introduced defects should lie in the middle of a reasonably thick insulator to improve the carrier energy selectivity.