Evaluation of recombination velocities of grain boundaries measured by high resolution lock-in thermography

摘要

Multicrystalline silicon solar cells include a high amount of crystal defects such as dislocations and grain boundaries, which are featured by different degrees of recombination activity. This contribution presents a method to investigate the recombination velocity at grain boundaries (GBs) by means of dark lock-in thermography (DLIT). The local diffusion current density j_(01) at the GB is evaluated by applying a spatial decpnvolution algorithm and separating the dark current contributions due to their different voltage dependencies. Adopting a model of the GB developed by Lax enables an analysis of the recombination velocity from the local j_(01). In this contribution we firstly present an explicit expression for this calculation. It is shown that the dominant contribution to j_(01) at the investigated sample is caused by the recombination active GBs and that the intra-grain defects such as dislocations have just a lower influence.