Multifunctional Molecule Passivated Quasi‐2D Perovskite Film for Efficient and Stable Luminescent Solar Concentrator

Abstract Quasi−2D perovskite films with multiple quantum well structures can provide a large Stokes shift and efficient photoluminescence (PL), which have great potential in the application of luminescent solar concentrators (LSCs). However, its low photoelectric conversion efficiency and poor stability remain obstacles to commercial application. Here, a multifunctional molecule additive octyltriphenylphosphonium bromide is introduced to prepare high‐quality perovskite LSCs. The multifunctional molecule can simultaneously passivate perovskite cations and anions, reducing the defect sites and improving the photoluminescence quantum yield (PLQY) of the perovskite nanocrystals. Triphenylphosphine groups with high steric hindrance effect can hinder ion migration; the hydrophobic properties of the long alkyl chain prevent water erosion, which together improves the stability of the perovskite films. The multifunctional molecule passivated perovskite film has a high PLQY of 100% and retains 96% of the initial PL intensity after 30 days of indoor storage. The perovskite LSC device achieves a maximum optical efficiency of 6.5% at a geometric factor of 3.1. The findings open a new way to boost the performance of perovskite‐based LSCs.