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Analytical modeling of the temporal evolution of hot spot temperatures in silicon solar cells

: Wasmer, S.; Rajsrima, N.; Geisemeyer, I.; Fertig, F.; Greulich, J.; Rein, S.


Journal of applied physics 123 (2018), No.9, Art. 093105, 10 pp.
ISSN: 0021-8979
ISSN: 1089-7550
Journal Article
Fraunhofer ISE ()
PV Produktionstechnologie und Qualitätssicherung; Photovoltaik; Silicium-Photovoltaik; Messtechnik und Produktionskontrolle

We present an approach to predict the equilibrium temperature of hot spots in crystalline silicon solar cells based on the analysis of their temporal evolution right after turning on a reverse bias. For this end, we derive an analytical expression for the time-dependent heat diffusion of a breakdown channel that is assumed to be cylindrical. We validate this by means of thermography imaging of hot spots right after turning on a reverse bias. The expression allows to be used to extract hot spot powers and radii from short-term measurements, targeting application in inline solar cell characterization. The extracted hot spot powers are validated at the hands of long-term dark lock-in thermography imaging. Using a look-up table of expected equilibrium temperatures determined by numerical and analytical simulations, we utilize the determined hot spot properties to predict the equilibrium temperatures of about 100 industrial aluminum back-surface field solar cells and achieve a high correlation coefficient of 0.86 and a mean absolute error of only 3.3 K.