Perylenetetracarboxylic diimide functionalized CsPbCl₃:Mn²⁺ as multifunctional spectral conversion nanomaterials for efficient and stable perovskite solar cells

Enhancing the photovoltaic performance of perovskite solar cells (PSCs) via the strategy of spectral conversion garners significant attention in recent years. However, developing a spectral conversion layer with excellent stability and low series resistance remains challenging. Here, we propose a spectral conversion material termed perylenetetracarboxylic diimide functionalized CsPbCl₃:Mn²⁺ quantum dots (CMI), which is incorporated at the SnO₂/perovskite interface as a down-conversion layer. This innovation effectively resolves the trade-off between spectral conversion efficiency and electrical performance of the spectral conversion layer. CMI converts ultraviolet light into visible light that is more readily absorbed by the perovskite, thus enhancing the light utilization and reducing the ultraviolet-induced degradation of perovskites. The rough and hydrophobic surface of CMI can modulate nucleation site arrangement and enhance grain boundary mobility, resulting in perovskite films with larger and denser grains. Furthermore, the C=O groups in CMI simultaneously passivate the oxygen vacancies in SnO₂ and the Pb²⁺ dangling bonds at the buried interface of the perovskite, reducing recombination losses and facilitating charge carrier transfer and extraction, and further enhancing power conversion efficiency (PCE). Consequently, the PSCs incorporating CMI as a down-conversion layer achieve an improved PCE, which rises from 21.26% to 23.61%, along with enhanced stability.