Butylamine-Catalyzed Synthesis of Nanocrystal Inks Enables Efficient Infrared CQD Solar Cells

Area of Science:

• Materials Science
• Renewable Energy
• Nanotechnology

Background:

• Colloidal-quantum-dot (CQD) photovoltaic devices face charge recombination issues near the back junction.
• Graded architectures can mitigate recombination but are limited by solvent orthogonality in state-of-the-art CQD materials.

Purpose of the Study:

• To develop a novel CQD ink compatible with nonpolar solvents for implementing graded architectures.
• To enhance the performance of CQD solar cells and tandem devices through improved band alignment and charge extraction.

Main Methods:

• A new CQD ink was synthesized using a neutral donor ligand acting as a phase-transfer catalyst, enabling processing in nonpolar solvents.
• An efficient graded architecture with engineered band alignment was implemented in infrared (IR) CQD solar cells.
• The strategy was applied to small-bandgap IR CQDs in 4-terminal perovskite/cSi tandem solar cells.

Main Results:

• Optimized IR CQD solar cells (Eg ≈ 1.3 eV) achieved a power conversion efficiency (PCE) of 12.3%.
• The graded architecture improved the built-in field and charge extraction.
• A +5% PCE addition was demonstrated in 4-terminal tandem solar cells using solution-processed IR CQDs with a perovskite front filter.

Conclusions:

• The developed CQD ink and graded architecture strategy overcome previous material processing limitations.
• This approach offers a viable pathway to achieve over 23% PCE in 4-terminal tandem solar cells incorporating IR CQDs.
• The findings pave the way for next-generation high-efficiency solar energy conversion devices.