A Method for the Detection and Quantitative Estimation of Low Shunt Resistances via the Dark Spectral Response Measurement of Multijunction Photovoltaic Cells: Theory and Results

The spectral response (SR) measurement of multijunction photovoltaic (PV) devices presents additional challenges with respect to the SR measurement procedure for single junction devices. Several works have appeared in the literature since the 1980s, leading to the development of the ASTM standard test method E2236-05, the only standard available for such measurements to date. Measurement artefacts that typically appear when measuring the SR of multijunction cells without applying an appropriate forward voltage bias to the entire cell have been also analyzed in the past. Several papers have shown that a low shunt resistance of one component cell is the main cause of such artefacts. In this paper the authors show how to experimentally detect low shunt resistances of component cells of a multijunction PV device and theoretically estimate their values, by means of measurements of the "dark SR" (i.e. the SR measured with no bias light). The theoretical description of SR measurements on N-junction devices by means of N non-ideal diodes is revised. A specific example of a 2-junction device is modelled and results from the theory are quantitatively compared with the experimentally measured dark SR. As a result, the shunt resistances of the component junctions are estimated. Examples of the same theoretical analysis on 3-junction devices of various technologies are also given, together with experimental results for comparison. The generalization to the case with N>3 junctions is also analyzed and presented.

PRAVETTONI Mauro;  MUELLEJANS Harald; 

2012-08-08

IEEE

JRC63200

https://publications.jrc.ec.europa.eu/repository/handle/JRC63200,