(461e) Controlling Phase Purity and Crystal Orientation of 2D Perovskite Thin Films By Additive Engineering

Metal halide perovskites have shown promising optoelectronic performance in photovoltaic devices together with low-cost film fabrication. The performance of lab scale 3D perovskite solar cells (PSCs) has reached very high levels exceeding 25 % power conversion efficiencies (PCE) with the use of various kinds of effective fabrication methods and techniques. However, commercialization of these devices is not yet possible due to their long-term instability to environmental conditions. 2D perovskites with bulky organic cations sandwiched between perovskite layers provide great long-term stability due to the moisture resistance nature of the bulky cations. Yet, 2D perovskites have complications in efficiency due to the presence of impurity phases and low degree of preferred vertical orientation of phases. Here, we use organic additives in the precursor solution to control the phase purity and the crystallographic orientation of 2D perovskite thin films. Optical and structural characterization methods were employed to identify the different phases present in the perovskite layer, and their crystallographic orientation. Our results show that organic additives can induce highly oriented crystal growth of 2D perovskites while reducing the amount of impurity phases. Our results demonstrate that the interaction of organic additives with the perovskite precursor species has a significant effect on the crystallization process leading to better control over the thin film structures.