A polarized near-infrared organic phototransistor based on a narrow-band SnPc single crystal†

Abstract

Near-infrared (NIR) organic photodetectors have emerged as one of the most promising candidates for next-generation light sensing by virtue of their unique properties, such as tailorable optoelectronic properties, large-area-preparability, compatibility with flexible substrates, and operation at room temperature. Limited to their poor exciton diffusion and dissociation, the bulk heterojunction architectures are always employed for most organic photodetectors. However, this amorphous film morphology has disadvantages in terms of operation speed and polarization properties. Here, we fabricated a fast and broadband organic photodetector with NIR response and polarization-sensitivity based on a narrowband SnPc single crystal. The device exhibits a good broadband response across the visible to NIR range (405–980 nm), and the NIR response can reach up to 38.5 A W⁻¹ at 850 nm, with a fast response speed of 440/590 μs and a specific detectivity of 10¹⁰ Jones. At a low light irradiation of 980 nm, the maximum responsivity is about 2.6 A W⁻¹, with the rise/decay times of 3.5/3.4 ms. In particular, benefiting from the anisotropic molecular stacking and charge transport of the SnPc single crystal, the device exhibits excellent polarization detection performance, and the linear dichroic ratios are 2.1 and 1.9 at 850 and 980 nm, respectively. Depending on this fast and polarized NIR response, high-resolution polarization imaging is demonstrated. Our work suggests that a high-quality narrowband organic single crystal is a promising platform for future polarization-sensitive NIR photodetection technology.