# Synthesis, Structure and Photoluminescence Properties of 2D Organic-Inorganic Hybrid Perovskites
## 3 Results and Discussion  
### Structure Characterization  
Figure 3a,c,e,g shows crystal structures of (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbCl\({}_{4}\), (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\), (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\) and (C\({}_{4}\)H\({}_{9}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\), respectively. It can be observed that the four perovskites exhibit two-dimensional layered structures. [PbX6] octahedrons are connected by common vertices, and organic amine cation is evenly filled on both sides of the octahedron in opposite ways. The molecular layers of (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbCl\({}_{4}\) and (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\) stack along the axis. The molecular layers of (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbI\({}_{4}\) stack along the b axis. The molecular layers of (C\({}_{4}\)H\({}_{9}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\) stack along the c axis. The organic amine cation of (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\) showed disorder and occupied two equivalent positions. The organic amine cation of (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbCl\({}_{4}\), (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbI\({}_{4}\) and (C\({}_{4}\)H\({}_{9}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\) showed order and occupied an equivalent position. Figure 3b,d,f,h shows the basic unit structure of (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbCl\({}_{4}\), (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\), (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbI\({}_{4}\) and (C\({}_{4}\)H\({}_{9}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\). The bond lengths are given in Table 1.  
Figure 2: The experiment optical path of photoluminescence test system. Figure 4a-d shows X-ray powder diffraction patterns of (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbCl\({}_{4}\), (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\), (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbI\({}_{4}\) and (C\({}_{4}\)H\({}_{9}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\), respectively. The diffraction peaks of (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbCl\({}_{4}\) powder appear at 6.52\({}^{\circ}\), 10.52\({}^{\circ}\), 15.80\({}^{\circ}\), 21.12\({}^{\circ}\), 26.49\({}^{\circ}\), 31.92\({}^{\circ}\) and 37.42\({}^{\circ}\); these diffraction peaks correspond to the crystal surface of the vertical x axis in (200), (400), (600), (800), (1000), (1200) and (1400). The diffraction peaks of (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\) powder appear at 6.41\({}^{\circ}\), 10.63\({}^{\circ}\), 15.96\({}^{\circ}\), 21.32\({}^{\circ}\), 26.72\({}^{\circ}\), 32.18\({}^{\circ}\) and 37.73\({}^{\circ}\). These diffraction peaks correspond to the crystal surface of the vertical a axis in (200), (400), (600), (1000), (1200) and (1400). The diffraction peaks of (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbI\({}_{4}\) powder appear at 6.14\({}^{\circ}\), 12.29\({}^{\circ}\), 18.48\({}^{\circ}\), 24.73\({}^{\circ}\), 31.05\({}^{\circ}\)and 37.47\({}^{\circ}\). These diffraction peaks correspond to the crystal surface of the vertical b axis in (020), (040), (060), (080), (0100) and (0120). The diffraction peaks of (C\({}_{4}\)H\({}_{9}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\) powder appear at 6.42\({}^{\circ}\), 12.85\({}^{\circ}\), 19.33\({}^{\circ}\), 25.87\({}^{\circ}\) and 32.50\({}^{\circ}\). These diffraction peaks correspond to the crystal surface of the vertical c axis in (002), (004), (008), (0010) and (0012). The X-ray powder diffraction results show that the four perovskites with sharp diffraction peaks have very high crystallinity. As shown in Figure 4a, the diffraction peaks of (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbCl