A multiband NIR upconversion core-shell design for enhanced light harvesting of silicon solar cells

Area of Science:

• Materials Science
• Nanotechnology
• Photovoltaics

Background:

• Lanthanide upconversion (UC) is explored to enhance silicon solar cells (SSCs) in the near-infrared (NIR) region.
• Conventional UC materials face limitations due to narrow NIR excitation bandwidth and low UC efficiency, hindering practical application.

Purpose of the Study:

• To design an efficient multiband UC system using lanthanide/ytterbium-doped core-shell upconversion nanoparticles (Ln/Yb-UCNPs).
• To overcome the limitations of conventional UC materials for improved NIR absorption in SSCs.

Main Methods:

• Developed Ln/Yb-UCNPs with distinct lanthanide ion (Ln3+) layers (Ho3+, Er3+, Tm3+) for broad NIR absorption (1100-2200 nm).
• Investigated a synthetic electron pumping (SEP) effect involving Yb3+ for enhanced UC efficiency through energy transfer and cross-relaxation.
• Integrated Ln/Yb-UCNPs into SSCs and evaluated their performance under standard AM 1.5G irradiation.

Main Results:

• Achieved broad multiband absorption spanning ~500 nm within the 1100-2200 nm range.
• Identified SEP effect enhancing UC efficiency by transferring electrons to Yb3+ excited states, yielding intense ~980 nm luminescence.
• Demonstrated SSCs with Ln/Yb-UCNPs achieved the largest reported NIR response range (up to 2200 nm) and a 0.87% absolute efficiency increase (19.37% total).

Conclusions:

• The developed multiband Ln/Yb-UCNPs effectively address bottlenecks in UCNP-coupled SSCs.
• This approach offers a viable strategy to significantly extend the NIR response and enhance the photovoltaic efficiency of silicon solar cells.