Stable <i>P</i> ‐Type PbS Quantum Dot Ink for all‐Blade‐Coated Short‐Wavelength Infrared Photodiodes

Abstract

ABSTRACT PbS colloidal quantum dots (CQDs) hold strong promise for short‐wave infrared (SWIR) optoelectronics. However, current photodetectors rely on p ‐type CQD layers fabricated via a laborious, defect‐prone layer‐by‐layer process. While robust n ‐type CQD inks have been realized, p ‐type inks remain challenging due to the absence of suitable ligands and solvents. An ideal solvent must ensure colloidal stability and be orthogonal to underlying layers. Here, we report a thiolate‐capped p ‐type PbS CQD ink using mercapto‐2‐propanol as the ligand and hexafluoro‐2‐propanol as the solvent. Stabilization arises from ligand–solvent hydrogen bonding, providing a shelf‐life exceeding six days. The solvent does not compromise pre‐deposited layers, enabling fully blade‐coated photodiodes in both n–p and p–n architectures. Devices fabricated with this ink exhibit a twofold increase in specific detectivity (2.55 × 10 12 Jones) and a 70% enhancement in bandwidth (155 kHz) compared to layer‐by‐layer controls, attributed to improved film morphology and charge transport.