Optical Characterization of Different Thin Film Module Technologies

Table 2

Comparison of characterization methods.

⊕	⊖
Electroluminescence (EL)
(i) High resolution; (ii) Identifiable; (a) Faulty laser scribing; (b) Process failures (e.g., shunts, layer defects, and TCO corrosion)	(i) Origin of a defect is not identifiable; (ii) Difficult to determine influence of defects on cell/module performance; (iii) Unremarkable EL-images sometimes supply IR-images with hot areas; (iv) Electrical contact necessary
Photoluminescence (PL)
(i) Contactless; (ii) Identifiable; (a) Material properties (e.g., reduced minority carrier diffusion length); (b) Process failures	(i) Homogenous illumination source necessary; (ii) Module measurements; Each cell separately
Infrared thermography (IR)
(i) Contactless (illuminated); (ii) Identifiable; (a) Different thermal behavior; (b) Shunts; (c) Hot spots; (d) Inactive cell parts; (e) Moisture	(i) Not contactless (dark); (ii) Not all defects (EL) lead to a temperature increase; (iii) High temperature area: not always the origin of defects; (iv) Difficult to determine exact position of defects or large number of small spots; (v) Not distinguishable between low shunt and high series resistance
Dark lock-in thermography (DLIT)
(i) Identifiable; (a) Different thermal behavior; (b) Process failures (e.g., shunts); (ii) Origin of a defect being identifiable	(i) Not contactless; (ii) Difficult to detect exact position of defects of large number of small spots; (iii) Long measurement period