Harvesting Sub-bandgap Photons via Upconversion for Perovskite Solar Cells

Area of Science:

• Materials Science
• Photovoltaics
• Photonics

Background:

• Lanthanide-based upconversion (UC) is crucial for harvesting sub-bandgap near-infrared photons in solar cells.
• Perovskite solar cells (PSCs) offer high efficiency but can benefit from extended spectral response.

Purpose of the Study:

• To investigate the implementation of UC in PSCs using a BaF2:Yb3+, Er3+ single crystal.
• To quantify the enhancement in photovoltaic performance due to upconverted photons.

Main Methods:

• A BaF2:Yb3+, Er3+ single crystal was integrated at the rear of a perovskite solar cell.
• The device was illuminated with 980 nm sub-bandgap photons and simulated terrestrial sunlight.
• Short-circuit current density enhancements were measured at varying sub-bandgap light intensities.

Main Results:

• The BaF2:Yb3+, Er3+ crystal emitted upconverted photons between 520-700 nm upon 980 nm illumination.
• An enhancement of 0.38 mA/cm2 in short-circuit current density was observed at lower sub-bandgap intensities.
• A significant enhancement of 2.09 mA/cm2 was achieved at higher sub-bandgap intensities, demonstrating non-linear scaling.

Conclusions:

• Integrating BaF2:Yb3+, Er3+ fluoride single crystals for UC is a viable strategy to enhance PSCs.
• This method effectively extends PSC response to near-infrared illumination, boosting current output significantly at high intensities.