Halide Re-Shelled Quantum Dot Inks for Infrared Photovoltaics

Area of Science:

• Materials Science
• Nanotechnology
• Photovoltaics

Background:

• Colloidal quantum dots (CQDs) are explored for tandem solar cells, complementing silicon and perovskites.
• Solution-processed infrared-bandgap CQD inks face challenges with agglomeration and fusion during solvent exchange.
• Robust surface protection is crucial for stable CQD inks in device fabrication.

Purpose of the Study:

• To develop a novel ligand exchange strategy for infrared-bandgap colloidal quantum dot inks.
• To prevent agglomeration and fusion during solution processing for enhanced solar cell fabrication.
• To improve the stability and performance of CQD-based tandem solar cells.

Main Methods:

• Exchanged long oleic acid ligands for a mixed system of medium-chain ammonium and anionic chloride ligands.
• Reshelled the CQD surface with short halides and pseudohalide ligands for polar solvent transfer.
• Utilized absorbance, photoluminescence, and X-ray photoelectron spectroscopy for characterization.

Main Results:

• The developed ligand exchange method provides robust surface protection, preventing CQD aggregation.
• Exciton sharpness was retained, confirmed by absorbance and photoluminescence measurements.
• X-ray photoelectron spectroscopy confirmed effective halide capping of the CQD surface.
• The optimized CQD solar cells achieved a power conversion efficiency of 0.76% after silicon filtering.

Conclusions:

• The new ligand exchange method enables stable, solution-processed infrared-bandgap CQD inks.
• This approach significantly enhances the performance of CQD-based tandem solar cells.
• The findings pave the way for more efficient and scalable CQD solar cell technologies.