Luminescence imaging of polymer solar cells: Visualization of progressing degradation

We apply luminescence imaging as tool for the nondestructive visualization of degradation processes within bulk heterojunction polymer solar cells. The imaging technique is based on luminescence detection with a highly sensitive silicon charge-coupled-device camera and is able to visualize with time advancing degradation patterns of polymer solar cells. The devices investigated have been aged under defined conditions and were characterized periodically with current-voltage (I-V) sweeps. This allows determining the time evolution of the photovoltaic parameters and—in combination with the luminescence images—understanding differences in the observed degradation behavior. The versatile usability of the method is demonstrated in a correlation between local reduction of lateral luminescence and a fast decrease of the short-circuit current (Isc) due to the loss of active area. Differences in the degradation of photovoltaic parameters under varied aging conditions are discussed.