A monolithically integrated organic photodetector and thin film transistor

We demonstrate a vacuum deposited molecular organic photodetector (OPD) integrated with a top gate, bottom-contact, pentacene-based organic thin film transistor (OTFT) for use as a switchable organic passive pixel sensor in focal plane imaging arrays. The heterojunction OPD consists of a 110 Å thick film of the donor, boron subphthalocyanine chloride, and a 325 Å thick film of the acceptor, C60. The OTFT switch allows the photodetector to be switched between an active (ON) state with a light intensity dependent photocurrent peaking at 20 nA, and an inactive (OFF) state with current <50 pA, corresponding to an 8-bit dynamic range. The integrated device has a spectral coverage from wavelengths of 400–600 nm, and a pixel switching frequency >400 kHz. The integrated structure is fabricated at room temperature, making this circuit compatible with low cost, flexible plastic substrates.