Self‐Assembled Monolayer Assisted Biphasic Heterojunction Organic Photodiode for Panel‐Level Manufacturing of Active‐Matrix Optical Imager

Abstract Organic photodiodes (OPDs) have shown great promises for large‐area optical imagers attributed to ease of processing and tunable performance in a wide wavelength range. A biphasic heterojunction (BPHJ) OPD design, having a bulky heterojunction structure on top of a monophasic donor layer, is proposed in this work. The BPHJ structure is spontaneously formed on a self‐assembled monolayer (SAM) treated indium tin oxide surface by depositing the donor and acceptor layers sequentially. The fabricated OPDs present significantly reduced dark current and meanwhile improved specific detectivity with a larger linear dynamic range and faster response compared to the conventional devices. This strategy is proved to be universal to various donor/acceptor combinations, covering a wide range of wavelength from visible to near‐infrared. Such a BPHJ structure is well compatible for the back‐end‐of‐line integration processes on top of the TFT backplane from the semiconductor display fab. An active‐matrix imager with an ultralow detection limit can reproduce ideal image quality under an ultra‐low light intensity of nW cm −2 level.