Structural and Electronic Properties of Intertwined Defect in Ruddlesden–Popper 2D Perovskites Study Using Density Functional Theory Calculations

The lead halide perovskite material has recently drawn significant attention from the scientific community and has been employed as an active layer material for optoelectronic devices with a wide range of applications. Notably, in recent years, organic inorganic lead halide perovskite solar cell devices have reached power conversion efficiencies rivaling those of silicon-based ones. However, to this date environmental stability of these active layer materials has not yet been fully resolved, thereby hindering their commercialization. Recently, the 2D layered Ruddlesden–Popper type perovskite, has emerged as a possible alternative owing to its enhanced stability against the elements. However, despite of this advantage, devices employing this material have not yet matched the efficiency of their 3D counterparts, which can be explained by the possible presence of structural defects. The intertwined defects of 2D perovskites have been reported from experiments; however, there have been no detailed studies on the impacts of these intertwined defects on 2D perovskite. In this work, we performed series of large-scale ab-initio calculations of the intertwined structures and computed the formation energies of n = 1, n = 2 and n = 3 members. Decreasing intertwined structure formation energy with increasing 2D perovskite principle number implies higher stability of intertwined structures with increasing number of inorganic layers, which is consistent with experimental observations. Band structure calculations reveal flat dispersion curves along the a and c directions in the real space, indicating that the exciton transfer is confined to one direction. Hence, the present study revealed the stability of the intertwined defects and their potential impacts to the device performance, suggesting that careful control of the number of principle members is critical for preventing the formation of intertwined structures.