Improving Stability and Efficiency of Silicon Solar Cells by Integrating SiO2-Coated Lead-Free Cs3Bi2Br9 Perovskites Quantum Dots as Luminescence Down-Shifting Layer

Lead-based perovskite quantum dots (QDs) have promising applications in optoelectronic devices, but commercial applications are limited by the potential toxicity and poor stability of lead. Meanwhile, there are lattice, polarity, and thermal expansion coefficient mismatches in integrating semiconductor materials onto the surface of photoelectronic circuit devices, resulting in high-density defects limiting the reliability of photoelectronic devices. Therefore, there is a need to investigate perovskite alternatives that are non-toxic, stable, and can be effectively coupled to silicon photonic circuits. In this paper, lead-free perovskite Cs3Bi2Br9/SiO2 QDs were synthesized. The emission wavelength falls within the 400–560 nm range, exhibiting vibrant blue photoluminescence and demonstrating exceptional air stability for a duration exceeding 60 days. Optical tests and density-functional theory (DFT) calculations show that the silica shell layer effectively binds the electron and hole wave functions, prevents photon-generated carriers from escaping, reduces surface defects, and improves the carrier recombination probability. Meanwhile, using Cs3Bi2Br9/SiO2 QDs as a luminescent down-shifting (LDS) layer in combination with a conventional silicon solar cell, the photovoltaic conversion power was increased by 1.82%. Hence, the core-shell structure is designed by the green environmental protection method to control the improvement of the PL characteristics of QDs, which opens a window for the synthesis of new barrier materials in ethanol and water systems, making the Cs3Bi2Br9/SiO2 QDs have great potential for the application of novel optoelectronic devices in the future.