Vapor-treated PbS quantum-dot inks retain efficiency after 60 days

A brief treatment with butylamine vapor enabled lead sulfide quantum dots capped with lead iodide to be dispersed in amine-free solvents, producing inks with reported colloidal stability beyond 60 days under ambient storage. In the peer-reviewed materials study, solar cells fabricated with the aged ink retained a power conversion efficiency of 10.8%, approximately 90% of the efficiency obtained with freshly prepared ink. A control device using a conventional liquid butylamine ink declined to 0.3% efficiency within four hours.

The work addresses a formulation challenge in solution-processed near-infrared optoelectronics. PbS-PbI2 quantum dots are used in photovoltaics and photodetectors, but dispersing their surface ligands requires a strongly coordinating solvent. Butylamine can provide that function, although sustained contact with liquid butylamine etches the quantum-dot surface and compromises its integrity. Previous efforts reduced the butylamine content through co-solvent engineering, but the source reports that those approaches extended ink stability to only about one week.

Researchers from Northeast Normal University and Jeonbuk National University developed a vapor-assisted pre-solvation strategy that separates the initial solvation step from the final ink formulation. Instead of dispersing the PbS-PbI2 quantum-dot solids in liquid butylamine, the team exposed them briefly to low-boiling-point butylamine vapor. The transient treatment induced dissociation and solvation of the dense PbI2 ligand shell on the quantum-dot surface. The remaining butylamine was then completely removed through evaporation, after which the treated quantum dots could be dispersed directly in an amine-free polar solvent such as N-methylpyrrolidone.

Photophysical characterization showed that the vapor-processed inks had a markedly reduced trap-state density and a prolonged carrier recombination lifetime compared with conventional butylamine-solvent-based inks. Their average particle size showed no detectable change after more than 60 days of ambient storage, supporting the reported colloidal stability. The device results were consistent with that improved formulation behavior: ink stored for 60 days produced solar cells with 10.8% power conversion efficiency, while the conventional butylamine-ink control device fell to 0.3% within four hours. The source presents these measurements for the reported laboratory devices; it does not establish performance across other device architectures or storage conditions.

The vapor-processed ink also withstood temperatures as high as 80 °C and proved compatible with large-area deposition. The team produced uniform blade-coated films over 100 cm², demonstrating scalability under the reported processing conditions. By using butylamine temporarily to pre-solvate the ligand shell and then removing it before ink formulation, the method avoids prolonged liquid-phase contact while retaining the solvation needed for dispersion. The resulting PbS-PbI2 inks combined long-term colloidal stability, reduced surface etching, sustained device efficiency and uniform large-area coating, offering a practical formulation for solution-processed quantum-dot optoelectronics.

Subject of Research: Vapor-assisted formulation of stable PbS-PbI2 quantum-dot inks for near-infrared optoelectronic devices

Article Title: Vapor-assisted pre-solvation breaks stability limitation of PbS QD inks

Article References: Vapor-assisted pre-solvation breaks stability limitation of PbS QD inks. Original publication (Bibliographic details unavailable.)

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DOI: Not provided

Keywords: PbS quantum dots, quantum-dot inks, butylamine vapor, colloidal stability, near-infrared photovoltaics, solar cells, ligand pre-solvation, surface etching, blade coating, solution processing, Vapor-assisted, pre-solvation