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 similar to 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.