Strategic Selection of Functional Groups for Ligand Passivation to Improve Performance of Cesium–Lead–Iodide Quantum Dot Photovoltaics and Luminescent Solar Concentrators

Abstract CsPbI₃ perovskite quantum dots (PQDs) have emerged as promising candidates for photovoltaics (PVs), light‐emitting diodes (LEDs), and lasers owing to their phase stability and photoluminescence quantum yield being superior to those of bulk CsPbI₃. However, surface vacancies form during purification and ligand exchange pose challenges in attaining high moisture stability and efficiency. In this study, various surface passivation strategies involving the use of different compounds, such as hydroxyl ( ─ OH) and nitro ( ─ NO₂) groups and phenethylamine (PEA)‐based ligands are developed. Among these methods, treating the QDs with 4‐nitrophenethyl ammonium chloride (NO₂‐PEACl) results in the best PV performance, with power conversion efficiencies of 15.4% and 41.3% under 1‐sun illumination and a 1000‐lx LED, respectively, comparable to that obtained using bulk perovskite PVs under indoor light. NO₂‐PEACl passivation also enhances the photoluminescence intensity, effectively rendering these PQDs suitable for luminescent solar concentrator applications, with a high external quantum efficiency of 34.2%. Furthermore, NO₂‐PEACl improves their moisture stability, with the corresponding devices retaining over 82% of their initial efficiency after 720 h and luminescent solar concentrators retaining 88% after 30 h, demonstrating excellent photostability. The proposed ligand passivation approach is promising for enhancing the performance and durability of PV devices for practical applications.