Suppressing thermal degradation of CsPbBr ₃ quantum dot/EVA films <i>via</i> APTES-mediated interface engineering: toward efficient and stable luminescence down-shifting for silicon solar cells

Luminescence down-shifting technology is increasingly recognized as a crucial option for enhancing the efficiency of silicon solar cells. However, high-quality down-shifting materials, such as perovskite quantum dots, face challenges related to poor thermal stability. These materials tend to agglomerate into larger sizes, leading to the deterioration of the luminescence films at high temperature. Unlike introducing a protecting layer on perovskite quantum dots, we applied 3-aminopropyltriethoxysilane (APTES) as a direct capping agent for perovskite quantum dots in this work to achieve both efficient and stable composite down-shifting films. The interaction between APTES and CsPbBr₃ quantum dots is thoroughly analyzed using both experimental measurements and theoretical calculations. Due to the strong interaction between APTES and CsPbBr₃, an optimal amount of APTES effectively stabilizes the quantum dots. When mixed with ethylene-vinyl acetate (EVA) copolymer, the strong interaction between APTES and polymer chains could suppress the aggregation of CsPbBr₃ quantum dots and inhibit degradation of the composite film under heating. Upon coating on commercial crystalline silicon solar cells, the optimal CsPbBr₃ quantum dot/EVA composite film achieves an absolute efficiency by 1.00%, maintaining a 0.81% efficiency improvement even after annealing at 90 °C for 3 hours. In contrast, while the film without APTES shows an efficiency improvement of 0.63% at room temperature but experiences a decrease of 0.23% under the same heating conditions. This work provides a feasible strategy to enhance the thermal stability of CsPbBr₃ quantum dot/EVA composite films under high-temperature conditions, offering a promising path toward the commercial application of perovskite-based luminescence down-shifting films in silicon solar cells.