Multishell NaYF4@NaYF4: Yb, Er@NaYF4 upconversion nanoparticles for enhanced photovoltaic performance of CdTe solar cells

Lanthanide-doped upconversion nanoparticles (UCNPs) are extensively used in spectral conversion layers of photovoltaic (PV) devices to capture near-infrared (NIR) light. However, surface quenching effects and low upconversion quantum yield (UC QY) of UCNPs limit their utilizations in PV devices. In this work, novel multishell NaYF 4 @NaYF 4 : Yb, Er@NaYF 4 (CSS) UCNPs have been synthesized via thermal decomposition method. The CSS UCNPs exhibit enhanced UC emission intensity by 36.33 times and UC QY by 38 times with respect to those of NaYF 4 : Yb, Er UCNPs, with a significant increase in fluorescence lifetime. After incorporating CSS UCNPs with Cadmium Telluride (CdTe) solar cells, the device achieved a power conversion efficiency (PCE) of 16.02% under AM 1.5G illumination, a 5.9% increase compared to the bare CdTe solar cell, and exhibited more than a 76-fold enhancement in efficiency under 980 nm excitation. This study demonstrates the synergistic effects of the multilayer shell structural UCNPs with enhanced luminescence and engineered interfaces between CdTe and back electrode, offering a scalable strategy for efficient infrared-responsive photovoltaic devices.