Characterization of Interface Recombination Velocity in GaAs/InGaP Heterojunction Solar Cells Using Dark Curve Measurements

In this article, a method for obtaining the interface recombination velocity in a solar cell from a measurement of the dark curve is presented. The front interface recombinationSfbetween window and emitter of a GaAs-InGaP heterojunction cell passivated by an AlInP window is used to demonstrate the method. By choosing a proper emitter thickness, the equation for the dark saturation currentJ01reduces to two terms, one related to the bulk recombination and the other to the interface recombination. The growth direction (either upright or inverted) is found to have a huge influence onSfas a result of the formation of an interfacial layer in the inverted grown cells. It is also shown thatSfand, therefore, the optimum cell design strongly depend on the emitter doping level. Using the obtainedSfdata, an optimized cell configuration on the substrate and in a thin film has been calculated, leading to a 1% (absolute).