Impact of Host Composition, Codoping, or Tridoping on Quantum-Cutting Emission of Ytterbium in Halide Perovskite Quantum Dots and Solar Cell Applications

Recently, various lanthanide ions (Ln³⁺) have been successfully doped into perovskite quantum dots (PQDs), and the quantum-cutting emission of ²F_5/2-²F_7/2 for Yb³⁺with a measurable inner efficiency of more than 100% has been discovered and applied as the luminescent converter of solar cells, which has opened a new branch for the application of PQDs. In this work, to further improve the quantum-cutting efficiency of Yb³⁺, the codoping and tridoping methods were used to improve the quantum-cutting emission of PQDs. The Yb³⁺-Ln³⁺ (Ln = Nd, Dy, Tb, Pr, Ce) pair-doped CsPbCl_xBr_yI_3-x-y PQDs were fabricated, with all displaying excitonic emission, narrow-band emission of Ln³⁺ ions, and quantum-cutting emission of Yb³⁺ ions. It was interesting that Yb³⁺-Pr³⁺ as well as Yb³⁺-Ce³⁺ pairs could effectively sensitize the emission of Yb³⁺, owing to Pr³⁺ and Ce³⁺ ions offering intermediate energy states close to the exciton transition energy of the PQDs. After host composition optimization and tridoping investigation, overall emissions with a 173% photoluminescence quantum yield (PLQY) were obtained in the Yb³⁺-Pr³⁺-Ce³⁺-tridoped CsPbClBr₂ PQDs. Then, the tridoped PQDs were designed as the down-converter for CuIn_1-xGa_xSe₂ (CIGS) as well as the silicon solar cells, which leads to an enhancement of the power conversion efficiency (PCE) of as high as ∼20%. The modified CIGS was further employed to charge the smart mobile phone, which could largely shorten the charging time from 180 to 150 min. This finding is of great significant for expanding the application fields of the impurity-doped PQDs.