Surface structure of quasi-2D perovskite PEA_(2m)MA_(n-2m)Pb_nI_(3m) (n m)

摘要

Quasi-2D perovskites passivate the perovskite surface and improve the lifetime of perovskite solar cells. However, their detailed surface structures have never been reported. We studied the surfaces of the solution-processed quasi-2D PEA(2m)MA(n-2m)Pb(n)I(3n) (PEA: C6H5CH3CH2NH3, MA: CH3NH3) perovskites as well as the 2D perovskite formed on top of 3D MAPbI(3) with the thicknesses relevant to practical solar cell (n 400) using ultraviolet photoelectron and metastable-atom electron spectroscopies. We confirmed that PEA segregates to the surface and that the phenyl group (C6H5) covers the outermost surface of the quasi-2D perovskite. We discuss plausible structures from the concentration dependence of PEA.