Energy-Down-Shift CsPbCl₃:Mn Quantum Dots for Boosting the Efficiency and Stability of Perovskite Solar Cells

Parasitic absorption by window layer, electrode layer, and interface layer in the near ultraviolet (UV) region is no longer negligible for high-efficiency perovskite solar cells. On the other hand, UV-induced degradation is also a big component of cell instability. Herein, CsPbCl₃:Mn-based quantum dots (QDs) are synthesized and applied onto the front side of the perovskite solar cells as the energy-down-shift (EDS) layer. It is found that with very high quantum yield (∼60%) and larger Stokes shift (>200 nm), the CsPbCl₃:Mn QDs effectively convert the normally wasted energy in the UV region (300–400 nm) into usable visible light at ∼590 nm for enhanced power conversion efficiency (PCE). Meanwhile, conversion of the UV rays eliminated a significant loss mechanism that deteriorates perovskite stability. As a result, external quantum efficiency in the UV region is significantly increased, leading to an increased short-circuit current (3.77%) and PCE (3.34%). Furthermore, the stability of perovskite solar cells has also been improved from 85% to 97% of their initial efficiency after exposure in the UV region with 5 mW/cm² intensity by 100 h. In parallel, the organic and silicon solar cells coated by EDS QDs also both confirm the above conclusion with PCE enhancements of 3.21% and 2.98%, respectively. These results suggest that the CsPbCl₃:Mn QDs play a significant role in improving the efficiency and stability of photovoltaic devices. To our knowledge, this is the first report about CsPbCl₃:Mn QD-assisted perovskite solar cells.