Zdenek Machacek

Diagnostics of Homogeneity of Individual Layers of Large-Area Silicon Solar Cells Using Local Irradiation

This paper deals with the possibility of checking the recombination rate distribution over the area of power (large-area) solar cells from measured values of open circuit voltage VOC using local irradiation by monochromatic light of different wavelengths (LBIV-light beam initiated voltage). This method can provide information both about the distribution of the recombination centres in large-area solar cells and the surface recombination rate at the antireflection coating. From the VOC distribution, also position and extent of local defects can also be determined. The method can be used to investigate the influence of technology on characteristics of solar cells as an in-process checking with the aim of increasing efficiency and reliability of solar cells

Optimal resolution of LBIV/LBIC methods for diagnostics of solar cell homogeneity

Both LBIV and LBIC methods (light beam induced voltage and light beam induced current) are based on measuring either short circuit current <i>I</i> _sc or open circuit voltage <i>V</i> _oc under conditions of local illumination by monochromatic light of a proper wavelength. By positioning the illuminated spot, a map of either <i>I</i> _sc or <i>V</i> _oc can be obtained, from which it is possible to find the distribution of the recombination rate over the area of the solar cell. A map of either <i>I</i> _sc or <i>V</i> _oc , from which the distribution of recombination in individual layers of the cell structure can be found, should be measured within a relatively short time, and high resolution is desirable. This paper deals with the possibility of resolution adjustment for the LBIV method, and maps of crystalline silicon in these resolutions are presented.

A note on irradiance dependence of photovoltaic cell and module parameters

This paper provides an analysis of the irradiance influence on photovoltaic cell efficiency in dependence on the cell construction, using the standard equivalent circuit describing solar cell. The influence of the series resistance is discussed in details and results of simulations are completed with experimental result obtained by measuring crystalline silicon solar cells and in broad intervals of irradiance and temperature and measuring different types of PV modules in a broad interval of irradiance.

A note on solar cell diagnostics using LBIC and LBIV methods

LBIC and LBIV methods are widely used for diagnosing solar cell homogeneity. This paper deals with the possibility of conducting LBIC measurements on the LBIV measuring device. These two methods are compared theoretically, and also by looking at the maps of the examined solar cells. Attention is paid to the working point of the LBIC method, which applies not only for modified LBIV devices but for all measurements of short circuit current.

Determination of recombination centers in c-Si solar cells from dark I–V characteristics

For photovoltaic cells efficiency is the quality of material key ingredient. Impurities in this material create recombination centers which cut down the effective carrier charge lifetime. The method of dark current measurement, which is described in paper, can be used for dominant impurity determination.

Determination of recombination centres in c-Si solar cells from dark I-V characteristics

The grade of a solar cell depends mainly on the quality of the starting material. During the production of this material, many impurities are left in the bulk material and form defects, which act as generation-recombination centres or charge carrier traps. These defects influence the efficiency of solar cells. Therefore knowledge of the centre parameters, e.g., energy levels in the band gap, capture cross section and concentration, is very useful for solar cell engineering. In this paper emphasis is placed on a simple and fast method for obtaining these parameters using measurements of dark characteristics. Preliminary results are introduced, together with the difficulties and limits of this method.