Tuning the Excitonic Properties of the 2D (PEA)2(MA)n-1PbnI3n+1 Perovskite Family via Quantum Confinement

In atomically thin two-dimensional (2D) crystals, the excitonic properties and band structure scale strongly with the thickness, providing a new playground for the investigation of exciton physics in the ultimate confinement regime. Here, we demonstrate the evolution of the fundamental excitonic properties, such as reduced mass, wave function extension, and exciton binding energy, in the 2D perovskite (PEA)(2)(MA)(n-1)PbnI3n+1, for n = 1, 2, 3. These parameters are experimentally determined using optical spectroscopy in a high magnetic field up to 65 T. The observation of the interband Landau level transitions provides direct access to the reduced effective mass mu and band gap Eg. We show that mu increases with the number of inorganic sheets n, reaching the value of three-dimensional (3D) MAPbI(3) already for n = 3. Our experimental observations contradict the general expectation that quantum confinement leads to an enhanced carrier mass, showing another aspect of the unprecedented flexibility in the design of the electronic properties of 2D perovskites.

Automated summary

This study demonstrates the evolution of fundamental excitonic properties in 2D perovskites through experimental optical spectroscopy in high magnetic fields. The findings contradict the general expectation of enhanced carrier mass with quantum confinement, showing new flexibility in designing electronic properties.