# Synthesis, Structure and Photoluminescence Properties of 2D Organic-Inorganic Hybrid Perovskites
## 3 Results and Discussion
### Structure Characterization
\begin{table}
\begin{tabular}{c c c c c} \hline  & **(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\({}_{4}\)** & **(C\({}_{4}\)H\({}_{9}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\)** \\ \hline C1–C2 & 0.1463 & 0.1494 & 0.1481 & 0.1429 \\ C2–C3 & 0.1392 & 0.1385 & 0.1363 & 0.1482 \\ C3–C4 & 0.135 & 0.1386 & 0.1372 & 0.1438 \\ C4–C5 & 0.1369 & 0.1384 & 0.1342 & 0.1461 \\ C5–C6 & 0.1322 & 0.1389 & 0.134 & - \\ C6–C7 & 0.1412 & 0.1387 & 0.1358 & - \\ C7–C2 & 0.1371 & 0.1387 & 0.1367 & - \\ C1–N & 0.1521 & 0.1447 & 0.1507 & - \\ Pb–X1 & 0.2877 & 0.2998 & 0.3224 & 0.3005 \\ Pb–X2 & 0.2841 & 0.2979 & 0.3203 & 0.2938 \\ Pb–X3 & 0.2886 & 0.2982 & 0.3198 & 0.2973 \\ \hline \end{tabular}
\end{table} 
Table 1: Length of four samples. Figure 3: (**a**) The crystal structure diagram and (**b**) the basic unit structure diagram of (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbCl\({}_{4}\); (**c**) the crystal structure diagram and (**d**) the basic unit structure diagram of (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\); (**e**) the crystal structure diagram and (**f**) the basic unit structure diagram of (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbI\({}_{4}\); (**g**) the crystal structure diagram and (**h**) the basic unit structure diagram of (C\({}_{4}\)H\({}_{9}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\). The hydrogen linked to the carbon atom is omitted. are parallel to the bc plane (X00, X = 2, 4, 6.....), indicating that the (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\) has a strong preferential orientation, and the organic component and inorganic component grow and extend alternately in the bc plane to form a two-dimensional structure of the vertical a axis. As shown in Figure 4b, the diffraction peaks of (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\) are parallel to the bc plane (X00, X = 2, 4, 6......), indicating that the (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\) has a strong preferential orientation, and the organic component and inorganic component grow and extend alternately in the bc plane to form a two-dimensional structure of the vertical b axis. As shown in Figure 4d, the diffraction peaks of (C\({}_{4}\)H\({}_{9}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\) are parallel to the ab plane (00X, X = 2, 4, 6......), indicating that the (C\({}_{4}\)H\({}_{9}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\) has a strong preferential orientation, and the organic part is parallel to the inorganic part and extends in the ab plane. The organic component and inorganic component grow and extend alternately in the ab plane to form a two-dimensional structure of the vertical c axis [32; 35]. The thickness of the single layer in the molecular structure of perovskite is the length of one layer [PbX\({}_{6}\)] of octahedron plus two layers of organic amine cation. The interlayer spacing of perovskite molecules can be calculated by Bragg formula:  
\[2d\sin\theta=k\lambda \tag{6}\]  
Figure 4: The X-ray powder diffraction patterns (experimental view and theoretical view) of (**a**) (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbCl\({}_{4}\) (green), (**b**) (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\) (black), (**c**) (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbI\({}_{4}\) (blue) and (**d**) (C\({}_{4}\)H\({}_{9}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\) (red). where \(d\) is the interlayer spacing, \(\theta\) is the diffraction degree, k is the diffraction class, and \(\lambda\) is the wavelength of X-ray.