Stable P-Type PbS Quantum Dot Ink for All-Blade-Coated Short-Wavelength Infrared Photodiodes

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 × 1012 Jones) and a 70% enhancement in bandwidth (155 kHz) compared to layer-by-layer controls, attributed to improved film morphology and charge transport.