# Tightly Compacted Perovskite Laminates on Flexible Substrates via Hot-Pressing
## 3 Results and Discussion
To demonstrate that the properties of the delaminated samples--which were obtained by physically separating the laminates--do not change when compared with their laminates, we characterized the absorbance spectra of the laminated samples before and after the delamination process, as shown in Figure 1f. The absorbance curves of the laminated and delaminated samples are almost identical,  
Figure 1: (**a**) Schematic illustration of the lamination process of perovskite thin films on flexible substrates. (**b**) Horizontal and (**c**) vertical pulling pressure of perovskite laminates as a function of temperature and imposed pressure. (**d**) Metallurgical microscope and (**e**) SEM images of the pristine CsPbBr\({}_{3}\) thin film and the laminated CsPbBr\({}_{3}\) thin film at 90 \({}^{\circ}\)C and 10 MPa. (**f**) Normalized absorbance spectra of the laminate prepared at 90 \({}^{\circ}\)C and 10 MPa and the corresponding delaminated CsPbBr\({}_{3}\) film. which demonstrates that delaminated samples could act as a rational qualitative metric for lamination effects. The same method was also followed in the previous report [22]. To further understand the morphological change during the lamination process, we characterized the crystallinity of perovskite films before and after lamination using XRD. According to the powder diffraction file (PDF) card shown in Figure 2a, the peaks locating at 15.2\({}^{\circ}\), 21.5\({}^{\circ}\), 30.7\({}^{\circ}\), and 37.8\({}^{\circ}\) were assigned to the (100), (110), (200), and (211) planes of a typical CsPbBr\({}_{3}\) cubic structure, respectively. All CsPbBr\({}_{3}\) films with and without lamination exhibited three main diffraction peaks corresponding to the (100), (110), and (200) planes. No noticeable peak shift was observed after the heat-only process or the lamination process, indicating the absence of lattice macrostrain or homogenous changes in the crystal structure [28]. Although it is hard to rule out the possibility that the strain induced by hot-pressing might be released once the laminates were separated, such a possibility is quite small according to prior work [22]. In striking contrast, the heated or laminated CsPbBr\({}_{3}\) films gained sharper diffraction peaks compared to the pristine one, and the full widths at half-maximum (FWHMs) of the peaks were clearly narrowed, as summarized in Figure 2b. The peak of tetragonal two-dimensional phase CsPb\({}_{2}\)Br\({}_{5}\) at 11.67\({}^{\circ}\) reported in prior work [29; 30; 31] was not observed in our samples, which is attributed to a shorter period of heating time and the existence of PEO in our case. It is interesting to notice that heating perovskite film without applying pressure can also evidently decrease the FWHM values. Compared to the pristine film before lamination, the FWHMs of diffraction peaks at 15.2\({}^{\circ}\), 21.5\({}^{\circ}\), and 30.7\({}^{\circ}\) were reduced to 95%, 81%, and 65% of their initial values, respectively, at a heating temperature of 90 \({}^{\circ}\)C. When the heating temperature was 150 \({}^{\circ}\)C, the FWHMs of diffraction peaks at 15.2\({}^{\circ}\), 21.5\({}^{\circ}\), and 30.7\({}^{\circ}\) were reduced to 75%, 73%, and 49%, respectively. When heat and pressure were simultaneously applied, the FWHMs of the three peaks maintained the same decreasing trend. Since both increased crystallinity with fewer defects and a larger grain size with fewer grain boundaries can result in a sharper XRD peak [32], these results indicate that the grains in perovskite films were larger in size and crystallinity increased. Figure 2: **(a)** XRD patterns of the pristine CsPbBr\({}_{3}\) film and the separated laminates prepared under different conditions, and the corresponding histograms of XRD (**b**) FWHMs and (**c**) relative peak intensities of the (100), (110), and (200) planes. To judge the recrystallization and crystallization orientation change of the perovskite laminates, we compared the relative intensity of each peak in the same sample, as shown in Figure 2c.