Organic Near Infrared Photodiode Based on Tin Naphtalocyanine as Sensitive Layer

The organic photodiodes (OPDs) have the advantages of rich functional material, controllable light-sensitive wavelength, low cost, and can be prepared on a flexible substrate, and has an important application prospect in the aspects of image sensing, immune detection, optical communication. Near infrared (NIR) optical devices can be fabricated mainly by using narrow energy gap materials and organic near infrared dye doping. Metal phthalocyanine, metal naphtalocyanine/fullerene C60 planar heterojunctions (PHJs) were often used as the active layer of NIR OPD. In this paper, NIR OPD based on SnNc as near infrared photosensitive layer were studied, because of its excellent absorption efficiency in NIR region. Bi-layer SnNc/C60 PHJ based OPD exhibited a large dark current, resulting a low photosensitivity. To reduce the dark current of the device, CuPc was introduced as electron blocking layer in the device, and tri-layer CuPc/SnNc/C60 PHJ based OPD was studied. The device shows improved performance, such as a low dark current, a large photoresponsivity, photosensitivity, the external quantum efficiency and the specific detectivity. The improved performance of device can be attributed to the enhanced electron injection barrier at the interface of anode and CuPc electron blocking layer.