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

Abstract

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, InBr 3 and SbBr 3 . 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.

Dicarboxylic Acid‐Assisted Surface Oxide Removal and Passivation of Indium Antimonide Colloidal Quantum Dots for Short‐Wave Infrared Photodetectors

“…This confirmed the replacement of long OA ligands with shorter ligands and facilitated the electronic coupling between CQDs. The average edge‐to‐edge separation between CQDs after cascade‐ligand exchange was 1–1.5 nm, which is a reduction of 45–60 % compared to previously published results for a one‐step halide exchange [32] . The absorption peaks of MA‐treated and cascade‐exchanged CQD films were slightly red‐shifted compared to the OA‐CQD film (Figure 3b), also suggesting the enhanced CQD coupling.…”

“…Chemie previously published results for a one-step halide exchange. [32] The absorption peaks of MA-treated and cascade-exchanged CQD films were slightly red-shifted compared to the OA-CQD film (Figure 3b), also suggesting the enhanced CQD coupling. The absorption peak of onestep iodine-exchanged CQD film did not shift with respect to OA-CQDs.…”

InSb/InP Core–Shell Colloidal Quantum Dots for Sensitive and Fast Short-Wave Infrared Photodetectors

“…InSb is a III–V semiconductor, free of arsenic, and possesses a narrow direct band gap (0.17 eV), making it a promising contender, alternative to Pb and Hg compounds, to readily access the short-wave infrared. Despite its potential, there have been only a few reports on InSb CQD-based SWIR photodetectors, , most likely due to the challenging synthesis − and the high surface defect density of the obtained InSb CQDs due to the lower electronegativity of Sb compared to As and P, that renders passivation with ligands challenging.…”

Dicarboxylic Acid‐Assisted Surface Oxide Removal and Passivation of Indium Antimonide Colloidal Quantum Dots for Short‐Wave Infrared Photodetectors

“…The average edge-to-edge separation between CQDs after cascade-ligand exchange was 1-1.5 nm, which is a reduction of 45-60 % compared to previously published results for a one-step halide exchange. [32] The absorption peaks of MA-treated and cascade-exchanged CQD films were slightly red-shifted compared to the OA-CQD film (Figure 3b), also suggesting the enhanced CQD coupling. The absorption peak of onestep iodine-exchanged CQD film did not shift with respect to OA-CQDs.…”