International quality assurance efforts forum on thin film modules (Presentation Recording)

Photovoltaic module qualifications tests such as IEC 61215 and 61646 help in minimizing infant mortality. However, they do not guarantee useful lifetime over the warranty period. Highly accelerated stress testing (HAST) can be useful in exposing design and component weaknesses and consequently increasing the margin of the design. However, they do not duplicate the conditions experienced by the module and hence cannot be used for assuring the desired useful lifetime. Other attempts were concentrated on extending the existing tests such as damp heat test of 1000 hours at 85 0C and 85% RH. However, even though extending the test to 1250 hours may detect flaws that may occur in during field deployment, extending the test to 2000 and 3000 hours may cause failures that are not observed in the field. Therefore, the PV Module Quality Assurance Task Force (PVQAT) is trying to formulate accelerated tests that will be useful towards achieving the ultimate goal of assuring useful lifetime over the warranty period. Examples of accelerated stress tests and the failure modes that can be detected by them in crystalline silicon modules are as follows: damp heat test: corrosion, delamination, junction box adhesion; humidity freeze: delamination, junction box adhesion, insufficiently cured encapsulant; thermal cycles: broken interconnect, broken cells, electrical bond failure, junction box adhesion, potential for arcing. There are 12 groups working under the PVQAT. Of these the Group 8 deals with the Thin Film Module Reliability. It works on the following degradation issues that have been identified for Thin Film PV: corrosion including system voltage induced degradation, semiconductor junction diffusion, cell-to-cell; cell-to-outside interconnections and delamination (structural-macro and micro). The activities of Thin Film Module Reliability Group 8 will be presented.