Organic photodetectors with active layer patterned by lithography

Photodetectors based on organic semiconductors offer excellent sensitivity already with active layer thicknesses in the submicron range. High absorption coefficients together with processing temperatures below 150°C open possibilities for new form factors (e.g. flexible foil substrates) and integration on top of readout backplanes. In this work, we describe organic photodetectors (OPDs) with polymer and small molecule active layers patterned by photolithography. Instead of a plain active layer over the entire substrate, each device was isolated from its neighbors. Devices retained their properties after patterning, with μA/cm² dark current density at -2 V and external quantum efficiency up to 40% at 500 nm wavelength. Furthermore, two-color array with patterned small molecule photodetector stacks side-by-side with 20 μm pixel pitch was demonstrated. This fabrication approach enables multicolor photodetector arrays or integration of additional photodiodes on top of CMOS imagers, for example to extend the sensitivity spectrum.