5:00 PM - 6:40 PM
[22p-P07-15] Top Thermal Annealing of 2D/3D Lead Halide Perovskites: Anisotropic Photoconductivity and Vertical Gradient of Dimensionality
Keywords:perovskite, solar cell, orientation
Two dimensional perovskite solar cells (2D PSCs) have a long-term stability in air because large organic cations can block moisture penetration. However, the power conversion energy (PCE) is lower than 3D PSCs because large organic cations inhibit charge carrier transport. Here, we report the effect of top thermal annealing (TTA) on the anisotropy of 2D PVK evaluated by XRD, time-resolved microwave conductivity (TRMC) and device characteristics. The (0l0) peaks ascribed to the parallel orientation of 2D PVKs disappeared by TTA. This suggests either preferred out-of-plane orientation, decreased crystallinity, or surface segregation of 3D PVKs. Subsequently, we evaluated TRMC anisotropic photoconductivity by exposing the excitation light from either the surface or substrate side. 2D and 3D PVK were found to distribute on the substrate side and on the surface, respectively. In addition, TTA-PSC had a shorter stability than reference PSC, which supports the vertical segregation of 2D/3D PVK.