Advanced Local Characterization of Silicon Solar Cells

Abstract

Solar cells made from multicrystalline silicon material, which still represent the majority of solar cells produced today, are by nature inhomogeneous devices. Their bulk excess carrier lifetime, which decisively influences the short circuit current density, the saturation current density, and the effective bulk diffusion length, may vary from position to position by an order of magnitude or more. Moreover, such cells may contain ohmic shunts and, in particular in the edge regions, positions of significant depletion region recombination current. The classical local characterization method for solar cells is light beam‐induced current (LBIC) mapping. This method does not give direct information on factors influencing the dark current density. A reliable quantitative local characterization of inhomogeneous cells can be performed by combining dark lock‐in thermography (DLIT) with electro‐ and photoluminescence (EL and PL) imaging. In this contribution, the well‐established and the most recent findings on the application of these methods are reviewed and typical application examples are presented. It is shown that luminescence imaging is most appropriate for local series resistance imaging and for qualitatively imaging of all kinds of recombination‐active defects. DLIT, on the other hand, shows a lower spatial resolution, but is most appropriate for imaging local two‐diode parameters like depletion region‐ and bulk saturation current densities, the latter allowing to draw conclusions also to the local short circuit current density. A comprehensive local characterization of silicon solar cells is possible by applying both DLIT and luminescence imaging, which complement each other.

Toward Understanding Chalcopyrite Solar Cells via Advanced Characterization Techniques

“…[141][142][143][144][145][146][147][148] Local electrical properties such as the series resistance, shunt resistance, and various types of recombination have been evaluated using these analysis techniques, which allow to investigate local current-voltage characteristics and local efficiency properties. [149,150] Luminescence imaging using EL and PL detect radiative recombination, with dark points in images indicating less recombination of excess carriers either due to nonradiative recombination or leakages through weak diodes or shunts. As with the aforementioned EBIC, LBIC measures the local short-circuit current under illumination, and useful information regarding the quantum efficiency can be determined in this way.…”

“…In silicon solar cells, local loss analysis and efficiency prediction using combinations of imaging techniques have also been employed. [149,150] The resolution of imaging characterization techniques depends on the degree of focusing of the source and the performance of the detector. In general, those techniques show a resolution of micrometer to several tens of micrometers; however, sub-micrometer scale analysis is also possible using the designed equipment.…”

The Diagnosis of Shunt Defects in CIGS Modules Using Lock-In Thermography: An Empirical Comparative Study

“…However, each material and architecture presents unique challenges, with the results affected by the inherent material properties and defect type. Thus, recognizing these nuances is paramount to effectively apply diagnostic techniques across a wide variety of photovoltaic devices [5][6][7][8][9].…”

“…However, there remains a challenge in many laboratories where commercially available LIT systems are used without a comprehensive understanding of the respective strengths and drawbacks of each method. This study aimed to address this knowledge gap by conducting a comparative analysis of biased thermography and LIT, focusing on investigating shunt defects in CIGS modules [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19].…”

Low-Cost Three-Quadrant Single Solar Cell I-V Tracer

“…There are many different techniques for characterising photovoltaic (PV) solar cells in various aspects. Some are focused on the microscopical compositions of the cells and the influences on their macroscopical behaviours; others are directly on these macroscopical aspects [1][2][3][4][5]. From a practical point of view, the cell is used to produce electricity; this may be the most important aspect.…”