Narrowband Organic Photodiodes Based on Green Light Sensitive Squarylium

Organic photodiodes (OPD) are becoming promising candidates for narrowband detection to meet new requirements on detectors, such as smaller size, higher resolution, lower power consumption, and the ability to interact with a variety of interfaces. In this article, a new narrowband green-light sensitive squarylium material with donor–acceptor–donor structure and its application in photodiode are reported. Due to the material with intense and sharp absorption in the green color and simple single-layer structure, the device shows excellent color selectivity. The green EQE of the device reaches 66%, while the blue EQE is as low as 10%. The device also shows significantly low dark current of ∼5.4 nA·cm–2 at −2.5 V and high specific detectivity of 7.7 × 1012 Jones. The strategy for designing narrowband OPD can be extended to other wavelength region by replacing substituent group in the donor–acceptor–donor structure of the squarylium and using the single-layer structure.