Boosting photoluminescence efficiency in Yb³⁺-doped CsPbCl₃ Nanocrystals via metal chloride post-treatment for high-performance luminescent solar concentrators

Yb³⁺-doped perovskite nanocrystals (NCs) featuring quantum-cutting capability exhibit enormous potential for luminescent solar concentrators (LSCs) due to their theoretically achievable 200% photoluminescence quantum yield (PLQY). However, their practical applications are still limited by defect-assisted nonradiative recombination, insufficient exciton to Yb³⁺ energy transfer efficiency, and poor operational stability. Herein, we demonstrate a CdCl₂ post-treatment strategy to regulate the lattice structure and PL dynamics of Yb³⁺:CsPbCl₃ NCs. As a result, the PLQY is significantly enhanced from 125.3% to 177.4%, accompanied by an increase in exciton to Yb³⁺ energy transfer efficiency from 75.9% to 86.4%. In addition, the treated NCs exhibit substantially improved photostability and thermal stability, with the thermal activation energy increasing from 61.8 ± 6.2 to 90.9 ± 2.4 meV. Compared with ZnCl₂, NiCl₂, and CuCl₂ treatments, CdCl₂ shows uniquely superior enhancement of the exciton to Yb³⁺ energy transfer efficiency and Yb³⁺ emission. Flexible LSCs fabricated based on the treated NCs exhibit high visible transparency and efficient near-infrared (NIR) photon waveguiding and concentrating capability, achieving an internal optical efficiency exceeding 120% and delivering enhanced photovoltaic performance when coupled with silicon solar cells. This work provides an effective strategy for developing high-performance Yb³⁺-doped perovskite NCs and flexible transparent LSCs for building-integrated photovoltaics.