On the Origin of the Peak-and-Trough Signal in the Grain-Boundary Light-Beam-Induced-Current Characterization Technique – 2D Numerical Simulations

29th European Photovoltaic Solar Energy Conference and Exhibition; 25-30
The grain-boundary light-beam-induced-current (GB-LBIC) technique is a versatile method for simultaneous determination of grain and grain boundary (GB) properties in polycrystalline semiconductors and semiinsulators without the need of charge collection by p-n juctions or Schottky contacts. Here, the GB itself acts as charge collector and generates a characteristic peak-and-trough (PAT) current profile. We investigate by 2D optoelectronic numerical simulations the nature of this PAT signal on different models for the GB. We find that generally the charge at the grain-boundary that causes a built-in-field around the GB is responsible for the PAT signal. However, a PAT can also be generated for structures with a high resistivity GB or a high recombination GB, without built-in fields. Moreover, these findings will demonstrate that the GB-LBIC method allows the determination - in materials with grain boundaries - of the minority carrier diffusion length of the grain bulk, without being influenced by GB recombination.