Highly Efficient Vertical SnS₂ Nanoflake Photodetector Decorated with PbS Colloidal Quantum Dots

Tin disulfide (SnS₂) is a 2D material with excellent optoelectronic properties suitable for various solar conversion and sensing applications. SnS₂ has been used in photodetectors due to its high carrier mobility and bandgap of 2.2eV. In applications where the detection of longer wavelengths of light is desired, other materials such as lead sulfide quantum dots (PbS QDs) with tunable band gaps are used together with SnS₂ to maximize light absorption and charge collection. Although several reports have demonstrated high sensitivity and responsivity of few-layer-SnS₂/PbS QDs photodetectors, their large scale production has not been addressed. These devices are often made by mechanically exfoliating bulk SnS₂ and depositing narrow metal contacts using e-beam lithography, which are both not scalable. In this work, we have fabricated photodetectors from vertical SnS₂ nanoflakes grown by a scalable close space sublimation and decorated by colloidal PbS QDs. The SnS₂/PbS QD device is fabricated on SiO₂/Si substrates with gold contacts patterned using standard photolithography. These devices exhibit excellent responsivity, on-off ratios and transient response critical for a photodetector. Our work presents a scalable method of fabricating photodetectors from SnS₂ nanoflakes and PbS QDs.