Impact of functional groups in spacer cations on the properties of PEA-based 2D monolayer halide perovskites

Incorporating low-dimensionalization technologies effectively tackle the challenge of inadequate long-term stability in hybrid halide perovskites, however their wide bandgap and strong quantum well confinement remain substantial obstacle for various optoelectronic applications. Addressing these issues without compromising long-term stability has emerged as a pivotal focus in materials science, in particular exploring the effects of the functional groups within spacer cations. Our simulations reveal that the robust π-π stacking interactions involving PEA and the strong hydrogen bonding interactions between PEA and MX contribute to narrowing the electronic bandgap in 2D monolayer PEAMX (e. g. 2D monolayer PEASnI: 1.34 ​eV) for reasonable visible-light absorption while simultaneously ensuring their favorable long-term stability. Moreover, the delocalized orbitals and relatively high dielectric constants in PEA, attributed to the conjugated benzene ring, has been observed to weaken the potential barrier, exciton binding effect and quantum well confinement in 2D monolayer PEAMX, thus facilitating photogenerated electron-hole separations and out-of-plane carrier transport. The impact of spacer cations on the optoelectronic and transport properties of 2D monolayer perovskites highlights the critical role of meticulously chosen and well-designed spacer cations, especially functional groups, in shaping their photophysical properties and ensuring long-term stability even under extremely operating conditions.