One shot mapping of minority carrier diffusion length in polycrystalline silicon solar cells using electroluminescence

Abstract

SThe novel technique of analyzing the spatial distribution of minority carrier diffusion length was investigated in detail by utilizing the photographic surveying of electroluminescence emitted from polycrystalline Si cells. The emitted infrared light (peak wavelength: 11 50 nm) from a sample cell under the forward bias was captured by a cooled CCD camera. The intensity was found to be proportional to the minority carrier diffusion length regardless of the running current density, which gave the quantitative information of the minority carrier diffusion length distribution with high reliability. The deteriorated areas andlor aggregation of defects were detected by a simple one-shot capturing of the emitted light.

Microcracks in Silicon Wafers II: Implications on Solar Cell Characteristics, Statistics and Physical Origin

“…In addition to specific I-V characteristics, the microcracks are also classified in terms of their appearance in electroluminescence (EL) images [13] taken of the finished solar cells, which may vary strongly as already observed in different studies [14]- [17]. To investigate the physical origin of shunts at microcracks in more detail, correlative microscopy techniques are applied.…”

High-Pressure Water Vapor Heat Treatment for Enhancement of SiOx or SiNx Passivation Layers of Silicon Solar Cells

“…The HWT effect was also investigated two-dimensionally using the electroluminescence (EL) imaging method. 9,10) The EL emission intensity relates to the effective diffusion length of minority carriers. Therefore, by EL intensity mapping, we can investigate the minority carrier diffusion length distribution and, thus, can detect cracks, electrode breakages, and electronically active crystallographic defects such as grain boundaries, dislocation clusters, and precipitates as dark areas in EL images.…”

From EBIC images to qualitative minority carrier diffusion length maps

“…The drawbacks of this method is the use of high beam energies which strongly increases the electron hole pair generation volume and decreases the spatial resolution, and the doping layers which have to be uniform all along the sample depth. Other methods based on electroluminescence [16] or microwaves [17] were developed; however, to our knowledge, no minority carrier diffusion length mapping methods has been developed by using one single EBIC image acquisition. The purpose of this work is therefore to propose an original method that permits to extract the minority diffusion length map from an unique EBIC picture, with the possibility to study non-uniformly doped sample.…”