Solution-Processed InSb Quantum Dot Photodiodes for Short-Wave Infrared Sensing

Short-wave infrared (SWIR) photodiodes (PDs) based on colloidal semiconductor quantum dots (QDs) are characterized by the great possibility of device operation at a voltage bias of 0 V, spectral tunability, possible multiple-exciton generation, and high compatibility with printable technology, showing significant benefits toward medical applications. However, the light-absorbing layers of those PDs are hampered by a reliance on RoHS-restricted elements, such as Pb and Hg. Here, we report the SWIR PDs with light-absorbing layers of InSb QDs synthesized by a hot-injection approach using a combination of precursors, InBr3 and SbBr3. Impurity-free and secondary phase-free synthesis was realized by optimized reaction temperature and time, precursor ratio, and quenching of reaction. The diameters of the QDs were controlled in the 5.1–7.8 nm range for strengthened confinement of photogenerated carriers and tuning of bandgaps between 0.64 and 0.98 eV. These QDs were processed to terminate their surfaces with small molecular ligands, giving a narrow interparticle distance between neighboring QDs in a light-absorbing layer sandwiched by carrier transportation layers. The resulting PDs achieve a photoresponse of ∼550 ms at 0 V, with combining the best values of responsivity and external quantum efficiency of 0.098 A/W and 10.1% under a bias voltage of −1 V at room temperature even in ambient air.