PID Testing Method for Solar Cells and Modules

Testing

© Fraunhofer CSP

Thermography image of a solar module suffering the PID defect.

In order to reduce the enormous effort and resource consumption for PID tests, in 2013 researchers at Fraunhofer CSP developed an easy-to-use PID test method for silicon solar cells. The method is characterized in particular by the fact that it works without the cost-intensive production of complete solar modules and their testing in large, specially operated climate chambers. Instead, during PID cell test single-cell encapsulated solar cells are tested and exposed to the exact same conditions which are known to cause PID: elevated temperatures and a high electrical potential between glass surface and solar cell. For this purpose, the layer stack structure of a solar module is simulated on the solar cell. Thus, the PID effect can be provoked on a smaller area and the possible degradation can be measured in real time. Furthermore, the effect of different polymer encapsulation films or glasses on the PID resistance of solar modules can be tested as well.

Root Cause Analysis

© Fraunhofer CSP

Cross-sectional TEM characterization of PID shunts.

© Fraunhofer CSP

Microscopic light beam induced current (µLBIC) image shows local recombination activity on the back of a bifacial cell after PID test.

PID of the shunting type (PID-s)

 

The physical mechanism of potential-induced degradation with shunting of solar cells (PID-s) remained unclear for a long period. Microstructural investigations on cell level with substantial contributions of Fraunhofer CSP revealed important facts regarding the origin of PID-s. Investigations revealed that stacking faults decorated with sodium cause PID-s. Based on this, a physical model for the shunting mechanism in PID-s affected solar cells is developed.

 

 

 

 

 

PID of the de-passivation type (PID-p)

 

Investigations have shown that bifiacial silicon solar cells develop PID on their backside under voltage stress, which is accompanied by a strong reduction of the surface passivation (PID-p). First microstructural investigations suggest local recombination active defects. The elucidation of the defect mechanism is the subject of current and planned investigations. The following link summarizes present results: Bifa-PID Testing.pdf

Publications

  • V. Naumann, C. Hagendorf, S. Großer, M. Werner, J. Bagdahn, Micro Structural Root Cause Analysis of Potential Induced Degradation in c-Si Solar Cells, Energy Procedia 27, 1 (2012).
  •  J. Bauer, V. Naumann, S. Großer, C. Hagendorf, M. Schütze, O. Breitenstein, On the mechanism of potential-induced degradation in crystalline silicon solar cells, physica status solidi - Rapid Research Letters (RRL)  6 (8), 331, 2012.
  • V. Naumann et al., Microstructural Analysis of Crystal Defects Leading to Potential-Induced Degradation (PID) of Si Solar Cells, Energy Procedia 33, 76 (2013).
  • V. Naumann, D. Lausch, A. Graff, M. Werner, S. Swatek, J. Bauer, A. Hähnel, O. Breitenstein, S. Großer, J. Bagdahn, C. Hagendorf, The role of stacking faults for the formation of shunts during potential-induced degradation of crystalline Si solar cells, pss (RRL) 7 (5), 315, (2013).
  • V. Naumann, D. Lausch, A. Hähnel, J. Bauer, O. Breitenstein, A. Graff, M. Werner, S. Swatek, S. Großer, J. Bagdahn, C. Hagendorf, Explanation of potential-induced degradation of the shunting type by Na decoration of stacking faults in Si solar cells, Sol. Energ. Mat. Sol. Cells 120, 383 (2014).
  • D. Lausch, V. Naumann, A. Graff, A. Hähnel, O. Breitenstein, C. Hagendorf, J. Bagdahn, Sodium Outdiffusion from Stacking Faults as Root Cause for the Recovery Process of Potential-Induced Degradation (PID), Energy Procedia 55, 486-493 (2014).
  • V. Naumann, T. Geppert, S. Großer, D. Wichmann, H.-J. Krokoszinski, M. Werner, C. Hagendorf, Potential-Induced Degradation at Interdigitated Back Contact Solar Cells, Energy Procedia 55, 498-503 (2014).
  • V. Naumann, D. Lausch, A. Hähnel, O. Breitenstein, C. Hagendorf, Nanoscopic studies of 2D-extended defects in silicon that cause shunting of Si-solar cells, physica status solidi (c) 12 (8), 1103–1107, 2015.
  • V. Naumann, D. Lausch, C. Hagendorf, Sodium decoration of PID-s crystal defects after corona induced degradation of bare silicon solar cells, Energy Procedia 77, 397-401 (2015).
  • V. Naumann, C. Brzuska, M. Werner, S. Großer, C. Hagendorf, Investigations on the formation of stacking fault-like PID-shunts, Energy Procedia 92, 569-575 (2016).
  • W. Luo, Y. S. Khoo, P. Hacke, V. Naumann, D. Lausch, S.P. Harvey, J. P. Singh, J. Chai, Y. Wang, A. G. Aberle and S. Ramakrishna, Potential-induced Degradation in Photovoltaic Modules: A Critical Review,  Energy Environ. Sci. 10, 43-68 (2017). DOI: 10.1039/C6EE02271E
  • V. Naumann, O. Breitenstein, J. Bauer, C. Hagendorf, Search for Microstructural Defects as Nuclei for PID-Shunts in Silicon Solar Cells, Proceedings of 44th IEEE PVSC, Washington, DC (USA), in press (2017).