Engineering the Effective Mass in 2D Perovskites via Octahedral Distortion

Abstract

Two-dimensional (2D) perovskites are well-known for the broad tunability of their optoelectronic properties. One of the prime methods is templating the inorganic sublattice via a selection of organic spacers. Here, with the use of magneto-optical spectroscopy, we demonstrate the remarkable potential of distortion engineering to tune the effective mass in 2D perovskites. We show that the 2D perovskites containing benzotriazole-based organic cations are characterized by the lowest reduced effective mass that has been measured for a lead iodide 2D perovskite. This stems directly from the very low degree of octahedral distortion in this material system. The practically flat structure of inorganic sublattice with no measurable out-of-plane corrugation results in the reduction of reduced effective mass by 12% with respect to the reference structure of (PEA) 2 PbI 4. The reduction in the mass is naturally accompanied by a lower 1s exciton binding energy of ∼200 meV. ■ INTRODUCTION Two-dimensional (2D) layered metal-halide perovskites have raised significant attention as a more stable alternative 1−3 to their three-dimensional (3D) counterparts. 4,5 These natural quantum wells, which consist of octahedral metal-halide slabs separated by large organic spacers, are considered promising candidates for low-cost light emitters and for energy harvesting applications. 5−9 The improved stability of 2D perovskites is related to the hydrophobic nature of the large organic spacers, 5 which also offers an efficient means to tune the optoelectronic properties of these materials.