Yangning Zhang, Pan Xia, Benjamin Rehl, Darshan H. Parmar, Dongsun Choi, Muhammad Imran, Yiqing Chen, Yanjiang Liu, Maral Vafaie, Chongwen Li, Ozan Atan, Joao M. Pina, Watcharaphol Paritmongkol, Larissa Levina, Oleksandr Voznyy, Sjoerd Hoogland, Edward Hartley Sargent

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

  • General Medicine

Heavy‐metal‐free III‐V colloidal quantum dots (CQDs) are promising materials for solution‐processed short‐wave infrared (SWIR) photodetectors. Recent progress in the synthesis of indium antimonide (InSb) CQDs with sizes smaller than the Bohr exciton radius enables quantum‐size effect tuning of the bandgap. However, it has been challenging to achieve uniform InSb CQDs with bandgaps below 0.9 eV, as well as to control the surface chemistry of these large‐diameter CQDs. This has, to date, limited the development of InSb CQD photodetectors that are sensitive to >=1400 nm light. Here we adopt solvent engineering to facilitate a diffusion‐limited growth regime, leading to uniform CQDs with a bandgap of 0.89 eV. We then develop a CQD surface reconstruction strategy that employs a dicarboxylic acid to selectively remove the native In/Sb oxides, and enables a carboxylate‐halide co‐passivation with the subsequent halide ligand exchange. We find that this strategy reduces trap density by half compared to controls, and enables electronic coupling among CQDs. Photodetectors made using the tailored CQDs achieve an external quantum efficiency of 25% at 1400 nm, the highest among III‐V CQD photodetectors in this spectral region.

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