Distinctive Debye-Scherrer rings are observed in the 2D GIWAXS pattern of the BDA-based film, suggesting the crystallites in the matrix majorly exhibit random orientation (Figure ). In the corresponding 1D profiles, strong scattering peaks of δ-CsPbI3 and PbI2 crystallites are observed, indicating the predominance of these phases. Note that these peaks are relatively stronger than the 3D CsPbI3 peak at the lower incidence angles, suggesting these degradation products are located around the top of the film surface.