利用配體輔助再沉澱法開發準二維手性鈣鈦礦奈米材料與其性質探討

Abstract

近年來，手性鈣鈦礦因具備自旋選擇性電荷轉移(CISS)效應、圓偏振光發射(CPL)能力及光電轉換潛力而受到廣泛關注。然而，針對低維度如n＝2結構之手性L2Csn-1PbnBr3n+1鈣鈦礦的研究仍相對不足，主因在於手性配體難以穩定嵌入結構中，易導致結構崩解或手性訊號微弱。為克服此挑戰，本研究以(OLM)2Csn-1PbnBr3n+1為基礎，導入手性鹽類溴化甲基苄胺(methylbenzylammonium bromide, MBA:Br)，並調控非手性配體(OLA)與手性配體比例，以優化合成條件，成功製備出具穩定n＝2結構之手性鈣鈦礦材料。材料經XRD、TEM、FTIR、UV-Vis、PL、TRPL、CD及CPL等多種表徵方法分析，結果顯示，MBA:Br修飾顯著提升光致發光穩定性與手性吸收特性，且螢光穩定性為未修飾樣品的兩倍。Urbach能量下降及XRD訊號增強亦證實其缺陷濃度降低與結晶品質提升。綜合而言，(R/S)-MBA:Br修飾策略不僅能穩定n＝2手性鈣鈦礦結構，亦有助於增強其手性光學響應與光學穩定性，為發展高性能手性光電元件提供實驗基礎與設計參考。In recent years, chiral perovskites have garnered significant attention due to their spin-selective charge transfer (CISS) effect, circularly polarized light emission (CPL), and potential for optoelectronic applications. However, studies on low-dimensional chiral perovskites, particularly those with an n = 2 structure such as L2Csn-1PbnBr3n+1, remain limited. The primary challenge lies in the difficulty of stably incorporating chiral ligands into the perovskite lattice, which often results in structural degradation or weak chiroptical signals.To address this issue, this study employed (OLM)2Csn-1PbnBr3n+1 as the base structure and introduced the chiral salt methylbenzylammonium bromide (MBA:Br). By tuning the ratio between the achiral ligand (oleylamine, OLA) and the chiral ligand, the synthesis conditions were optimized, resulting in the successful fabrication of stable n = 2 chiral perovskite materials.The materials were comprehensively characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), UV–visible (UV-Vis) absorption, photoluminescence (PL), time-resolved photoluminescence (TRPL), circular dichroism (CD), and circularly polarized luminescence (CPL) spectroscopy. The results reveal that MBA:Br modification significantly enhances photoluminescence stability and chiral absorption features, with fluorescence stability being twice that of the unmodified samples. Additionally, the reduction in Urbach energy and the enhanced XRD signals confirm a decrease in defect density and improvement in crystallinity.In summary, the (R/S)-MBA:Br modification strategy not only stabilizes the n = 2 chiral perovskite structure but also strengthens its chiroptical response and optical stability, providing both experimental insights and design guidance for the development of high-performance chiral optoelectronic devices.