Injection in light beam induced current systems : An analytical model

Abstract

In LBIC systems, the evaluation of the injection level is necessary when operating in low injection for defect recombination studies or in defined standard illumination conditions (one or several suns for concentrator applications) for quantum efficiency evaluation. We demonstrate in this contribution that evaluating the laser beam induced injection based on uniform illumination condition can lead to several decades of error because of the lateral carrier diffusion. Based on a parallel beam approximation, we propose here an analytical model to evaluate the maximum of injection of a laser with its parametrization valid for most LBIC system settings and material quality. State of the art high resolution LBIC (HR-LBIC) systems have so sharply focused laser beams that the beam divergence cannot be neglected anymore in the injection calculation. Although providing a quantitative criterion to determine whether the beam divergence can be neglected, we provide a more advanced model for describing the injection of the laser that includes beam divergence.