Solution-Phase Hybrid Passivation for Efficient Infrared-Band Gap Quantum Dot Solar Cells

Area of Science:

• Materials Science
• Nanotechnology
• Renewable Energy

Background:

• Colloidal quantum dots (QDs) offer tunable band gaps for photovoltaics.
• Large-size lead sulfide (PbS) QDs with narrow band gaps are ideal for complementing perovskite and silicon solar cells due to their near-infrared absorption.
• Complex surface chemistry and evolving facet exposure (nonpolar (200) and polar (111)) in larger QDs hinder performance.

Purpose of the Study:

• To develop an effective surface passivation strategy for large-size, narrow band gap PbS QDs.
• To address the limitations of previous passivation methods that failed for larger QDs.
• To enhance the performance of solar cells utilizing PbS QDs.

Main Methods:

• A hybrid passivation strategy using inorganic lead triiodide (PbI3-) and organic 3-chloro-1-propanethiol (CPT) was employed.
• Charge balance calculations identified optimal QD band gaps for complementary absorption.
• The passivation strategy targeted both (111) and (200) facets of the QDs.

Main Results:

• Hybrid passivation significantly improved photophysical properties, including narrower excitonic and emission peaks and reduced Stokes shift.
• The organic ligand CPT enhanced colloidal stability and prevented QD fusion in solid films.
• A 94% increase in power conversion efficiency and a 74% increase in external quantum efficiency at the excitonic peak were achieved.

Conclusions:

• The hybrid passivation strategy effectively addresses the surface complexities of large-size PbS QDs.
• This approach enables the successful integration of narrow band gap QDs into high-performance solar cells.
• The findings pave the way for advanced photovoltaic devices leveraging quantum dot technology.