Metal halide perovskites have shown promising optoelectronic performance in photovoltaic devices, combined with low-cost film fabrication. Lab-scale 3D perovskite solar cells (PSCs) have achieved high power conversion efficiencies (PCE) exceeding 25% through various effective fabrication methods and techniques. However, the commercialization of these devices is not yet possible due to their long-term instability under environmental conditions. In contrast, 2D perovskites, with bulky organic cations sandwiched between perovskite layers, offer greater long-term stability due to the moisture-resistant nature of the bulky cations. Nevertheless, 2D perovskites face efficiency challenges due to the presence of impurity phases and a low degree of preferred vertical orientation of phases. In this study, we employ an organic additive, thiosemicarbazide (TSC), to control the phase purity and crystallographic orientation of 2D perovskite thin films. TSC is directly incorporated into the solution process of creating perovskite thin films. Optical and structural characterization methods were used to identify the various phases present in the perovskite layer and their crystallographic orientations. Our data indicate that TSC promotes the highly oriented crystal growth of low-dimensional 2D phases, enhancing phase purity by successfully inducing the desired 2D perovskite phase. Our results demonstrate that the interaction of TSC with perovskite precursors significantly affects the crystallization process, providing better control over the formation of impurity phases and the phase orientation.
