Crystal Orientation Drives the Interface Physics at 2/3-Dimensional Hybrid Perovskites.

Combining halide perovskites with tailored dimensionality into two/three-dimensional (2D/3D) systems has revealed a powerful strategy to boost the performances of perovskite photovoltaics (PVs). Despite the recent advances, a clear understanding on the intimate link between interface structure and physics is still missing, leading so far to a blind optimization of the 2D/3D PVs. Here, we reveal the impact of 2D/3D crystal alignment in driving the interface charge-recombination dynamics. The 2D crystal growth and orientation is manipulated by specific fluorination of the phenethylammonium (PEA), used here as the organic cation backbone of the 2D component. By means of time-resolved optoelectronic analysis from femto- to microsecond, we demonstrate a static function of the 2D as an electron barrier and homogeneous surface passivant, together with a dynamic role in retarding back charge recombination. Our results reveal a crucial dependence of such beneficial effect with the 2D crystal orientation, leading to an enhanced open circuit voltage (VOC) if 2D lies parallel on the 3D. Such findings provide a deep understanding and delineate precise guidelines for the smart design of multidimensional perovskite interfaces for advanced PV and beyond.