Organic heterojunction photodiodes exhibiting low voltage, imaging-speed photocurrent gain

We report the demonstration of fast and strong photocurrent gain in organic photodiodes with tailored charge blocking layers. The hole blocking layer between the anode and the photoactive layer leads to accumulation of photogenerated holes at its interface with the active layer, which causes a strong secondary electron injection from the anode and as such a high photocurrent gain. Using a bulk heterojunction of C-60 and copper phthalocyanine as the active layer, we have achieved photocurrent gains up to 500 across the visible spectrum and bandwidths on the order of 1 kHz, well above the imaging-compatible bandwidth (>60 Hz). (C) 2010 American Institute of Physics. [doi: 10.1063/1.3481407]