Harvesting Sub-bandgap Photons via Upconversion for Perovskite Solar Cells
Roja Singh, Eduard Madirov, Dmitry Busko, Ihteaz M. Hossain, Vasilii A. Konyushkin, Andrey N. Nakladov, С. В. Кузнецов, Amjad Farooq, Saba Gharibzadeh, Ulrich W. Paetzold, Bryce S. Richards, Andrey Turshatov
Abstract
Lanthanide-based upconversion (UC) allows harvesting sub-bandgap near-infrared photons in photovoltaics. In this work, we investigate UC in perovskite solar cells by implementing UC single crystal BaF2:Yb3+, Er3+ at the rear of the solar cell. Upon illumination with high-intensity sub-bandgap photons at 980 nm, the BaF2:Yb3+, Er3+ crystal emits upconverted photons in the spectral range between 520 and 700 nm. When tested under terrestrial sunlight representing one sun above the perovskite’s bandgap and sub-bandgap illumination at 980 nm, upconverted photons contribute a 0.38 mA/cm2 enhancement in the short-circuit current density at lower intensity. The current enhancement scales non-linearly with the incident intensity of sub-bandgap illumination, and at higher intensity, 2.09 mA/cm2 enhancement in current was observed. Hence, our study shows that using a fluoride single crystal like BaF2:Yb3+, Er3+ for UC is a suitable method to extend the response of perovskite solar cells to near-infrared illumination at 980 nm with a subsequent enhancement in current for very high incident intensity.