Colloidal InSb Quantum Dot Ink Enables III-V Group Bulk-Heterojunction Shortwave Infrared (SWIR) Photodetector

Infrared (IR) optoelectronics have become important owing to their various applications, such as recognition, autonomous driving, and quantum communications. Specifically, IR detection in the shortwave IR (SWIR) spectrum (i.e., 1550 nm) is significantly important for eye safety and long-range communications. To date, the II-VI and IV-VI (e.g., HgTe, PbSe, and PbS) groups of CQDs have been widely applied to SWIR optoelectronic devices, but the use of toxic elements such as Pb and Hg limits their commercial viability. Group III-V colloidal quantum dots (CQDs) (e.g., InAs, InSb) have recently attracted significant interest as SWIR materials due to their narrow bulk bandgap and lack of toxic elements such as Pb and Hg. Herein, we synthesized of InSb CQD using the modified continuous injection method approach. This approach enables for facile tuning of bandgap at a SWIR wavelength of up to 0.9 eV with diffusion growth via monomer flux. In addition, the surface of the InSb CQD was effectively passivated and a stable CQD ink was obtained through solution-phase ligand exchange using halides and thiolates. Finally, we demonstrated a bulk heterojunction (BHJ) structure using n-type and p-type III-V CQDs. The BHJ CQD solids exhibited broad absorption up to 1600 nm and a 6-fold higher responsivity compared to the pristine InSb CQD device due to efficient charge transport.