Fluctuations in photocurrent of bulk heterojunction polymer solar cells—A valuable tool to understand microscopic and degradation processes

We report electrical noise measurements from illuminated bulk heterojunction (BHJ) polymer based solar cells (PSC). These noise-studies of BHJ-PSCs provide considerable insight into the underlying charge transport processes. The power spectrum reveals a flicker noise of the form 1/fα at low frequencies (f 5 kHz. Photocurrent fluctuations were analyzed at different temperature, light intensity, and device conditions. A theoretical description employing kinetic Monte-Carlo simulations points to the importance of trap distribution and kinetics in the understanding of fluctuations in the low f regime.