新穎全無機二維層狀鈣鈦礦奈米晶體之研究

Abstract

近年來，除了塊材的二維層狀鈣鈦礦(Ruddlesden-Popper phase perovskite)之外，已經能夠使用低溫合成法製備膠體有機-無機二維層狀鈣鈦礦的奈米晶體，當材料為奈米晶體時，除了原本層狀結構固有的量子井現象之外，還因粒子達到奈米等級而具有量子侷限效應。然而，有機-無機二維層狀鈣鈦礦結構中的有機絕緣體會導致材料導電性不佳。因此本論文發展出以十八烷二酸(Octadecanedioic acid)取代部分油酸(Oleic acid)，並使用高溫注射法合成全無機二維層狀鈣鈦礦奈米晶體。由電子顯微鏡觀察到材料為大小約為100 nm的長方體，且其晶面間距(d-spacing)可以對應到X-光粉末繞射圖的繞射峰。最大放光波長在460 nm的位置，而從X-光粉末繞射圖繞射峰的等間距現象可以證實材料確實有二維層狀結構，將此與理論計算n=3的X-光粉末繞射圖做比對，可以發現兩者的繞射峰位置一樣。由於間隔劑由原本的長碳鏈有機材料轉換為無機的溴化銫，故能改善其導電性，以利後續的應用。During the past few years, two-dimentional organic-inorganic hybrid Ruddelsden-Popper perovskite (RPP) nanocrystals has been demonstrated by sol-gel synthesis. These nanocrystals are attracted broad attention about quantum confinement effect and self-assembly layered structure. The structure of nanocrystals consist of inorganic perovskite layers intercalated with organic cation bring appealing quantum-well effect. However, the organic cations are insulator that lead to poor electric performance. Here we present a new method to synthesis all inorganic RPP nanocrystals. The surface ligands of nanocrystals are exchanged partly from oleic acid to octadecanedioic acid under high-temperature injection method. The TEM images show a 100 nm rectangle and d-spacing match with X-ray diffraction (XRD) patterns. The PL of nanocrystals is about 460 nm. We claim that it is two-dimensional structure by the repeating unit of XRD patterns. The simulation confirm these nanocrystals XRD patterns and predict n=3 member of all inorganic RPP. The spacer of these nanocrystals is inorganic cesium bromide that improve electric performance.