Nondestructive Performance Characterization Techniques for Module Reliability

This paper describes nondestructive characterization techniques for module reliability. These techniques include light and dark current versus voltage and related analysis such as resistance, diode quality factor, and dark current. The use of the NREL laser scanner at zero volts and forward bias is also described as a technique to uncover cracks, shunts, and open-circuit regions in a module. Quantum-efficiency measurements of isolated cells or regions in a module are also possible. The interpretation of laser-scanning data is enhanced by hotspot testing with an infrared camera or thermographic paper. Specialized nondestructive techniques have also been developed to determine the shunt resistance of individual cells in a module by selective shading of cells under sunlight. Ultraviolet fluorescence and reflectivity measurements at NREL have proven useful in evaluating encapsulant stability.