Dual-Functional Coordination Polymer Nanoparticle Coatings for Downconversion and Antireflection in Silicon Solar Cells

Although the use of rare-earth materials for downconversion is a standard strategy to enhance ultraviolet (UV) harvesting, it suffers from high costs and complex manufacturing. In this work, we introduce a luminescent nanoscale coordination polymer (CP) material that serves as a dual-function overlayer for spectral down-conversion and antireflection. Photoluminescence measurements show emission at 450 nm under 369 nm of excitation. The external quantum efficiency (EQE) enhancement peaks near 370 nm, which matches the photoluminescence excitation (PLE) maximum. The nanoscale CP nanoparticles enable efficient light-matter interactions and wavelength conversion, facilitating improved photon utilization in the device. The efficient conversion of UV light to visible light generates carriers deeper within the depletion region and away from the surface, increasing the probability of carrier collection. Reflectance measurements confirm that the CP layer further reduces reflection on the textured silicon surface, indicating its potential to replace conventional antireflection layers. Under AM 1.5G illumination, the power conversion efficiency increases from 17.60% to 18.16%. This is driven by an increase in short-circuit current density from 33.68 to 34.70 mA/cm2. This work establishes the CP overlayer as a low-cost and nontoxic nanostructured dual-function coating that delivers both spectral downconversion and antireflection benefits.