Organic photodiodes operating in the near-infrared (NIR) region with an operating wavelength of about 850 nm, which corresponds to GaAs-based optical devices, were fabricated by wet process. In the active layer, Copper(II)5,9,14,18,23,27,32,36-octabutoxy-2,3-naphthalocyanine was used as NIR absorption material. A wide-bandgap polymer was doped to decrease the dark current, and an n-type organic semiconductor was doped to increase optical sensitivity. To decrease the dark current further, an electron-blocking layer was added onto the anode. This bi-layer structure was found to be very useful for decreasing the dark current. We also evaluated the on/off ratio, which is very important for application to optical communication devices.
Ultraflexible Near-Infrared Organic Photodetectors for Conformal Photoplethysmogram Sensors