Optical Characterization of Different Thin Film Module Technologies
Table 2
Comparison of characterization methods.
ā
ā
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