Limited laser beam induced current measurements: a tool for analysing integrated photovoltaic modules

Abstract

A new limiting laser beam induced current (li-LBIC) measurement technique is described which allows the recovery of the true signal in an integrated photovoltaic (PV) module. It is a measurement based on optically exciting the device by scanning with a laser, where the probed cell is brought under limiting condition by means of manipulating the background illumination. The signal obtained is directly proportional to the laser strength, which was previously unobtainable by typical LBIC measurements in a module. The advantages are shown to be that it gives an opportunity to measure the real properties of investigated cells and is usable for fully encapsulated, series connected photovoltaic modules. It is also unaffected by non-uniform background illumination. The system provides spatially resolved measurements and has shown to be an effective characterization tool to reveal spatial non-uniformity in the PV devices with sub-millimetre resolution. It can be employed as a characterization tool for commercial modules functioning not only for quality control of newly produced PV devices but also for loss analysis during various stages of their operating lives.

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