Miguel Ángel González

Smartphones as experimental tools to measure acoustical and mechanical properties of vibrating rods

Modern smartphones have calculation and sensor capabilities that make them suitable for use as versatile and reliable measurement devices in simple teaching experiments. In this work a smartphone is used, together with low cost materials, in an experiment to measure the frequencies emitted by vibrating rods of different materials, shapes and lengths. The results obtained with the smartphone have been compared with theoretical calculations and the agreement is good. Alternatively, physics students can perform the experiment described here and use their results to determine the dependencies of the obtained frequencies on the rod characteristics. In this way they will also practice research methods that they will probably use in their professional life.

Low-cost system for full-wafer photoluminescence characterization of photovoltaic silicon

Photoluminescence imaging technique has recently emerged as a powerful tool for obtaining very quick sorting of silicon based solar wafers and cells. In this work, we report on a low-cost photoluminescence imaging system, paying special attention to the different constituting elements. Results on both commercial multicrystalline (mc) and seed-monocast (sm) Si wafers and solar cells are discussed.

Photoluminescence Imaging and LBIC Characterization of Defects in mc-Si Solar Cells

Today’s photovoltaic market is dominated by multicrystalline silicon (mc-Si) based solar cells with around 70% of worldwide production. In order to improve the quality of the Si material, a proper characterization of the electrical activity in mc-Si solar cells is essential. A full-wafer characterization technique such as photoluminescence imaging (PLi) provides a fast inspection of the wafer defects, though at the expense of the spatial resolution. On the other hand, a study of the defects at a microscopic scale can be achieved through the light-beam induced current technique. The combination of these macroscopic and microscopic resolution techniques allows a detailed study of the electrical activity of defects in mc-Si solar cells. In this work, upgraded metallurgical-grade Si solar cells are studied using these two techniques.

Trapping activity on multicrystalline Si wafers studied by combining fast PL imaging and high resolved electrical techniques

Multi-crystalline Si is the preferred material in the photovoltaic world market due to the good balance between production costs and efficiency. However, it has a large number of defects acting as recombination centers for the photogenerated carriers. In this work, we use both the fast inspection provided by the photoluminescence imaging technique with the very high spatial resolution of the light beam induced current and electron beam induced current techniques, for obtaining a comprehensive understanding of the electrical activity and distribution of defects in this material.

Combined EL and LBIC Study of the Electrical Activity of Defects in Solar Cells Based on Innovative Wafers Grown by Casting Methods

In this paper we combine LBIC and EL measurements of commercially multi-crystalline silicon solar cells, in order to obtain detailed information about the electrical activity around defect areas. This integrated analysis is suitable for the study of different crystal defects at both micrometric and full wafer scale. In particular, the electrical activity of some defect areas is studied in detail by means of highly spatially-resolved LBIC maps, showing important differences in their behaviours. A discussion about the origin of these differences is presented.