Organic intercalation engineering of quasi-2D Dion-Jacobson alpha-CsPbI3 perovskites

The intrinsically poor stability of three-dimensional (3D) alpha-CsPbI3 perovskites (PVSKs) greatly hinders their application in solar cells and optoelectronics. Here, we propose a new series of compounds, quasi-2D Dion-Jacobson (DJ) CsPbI3 PVSKs, through density functional theory (DFT) calculation. The material design is based on periodic intercalation of tailored ethylenediamine cations (EDA(2+)) between the inorganic layers. The resultant quasi-2D (EDA)Csn-1PbnI3n+1 PVSKs exhibit fundamentally enhanced stability, owing to the strong I-H interaction of diamine cations with a shortened interlayer distance (similar to 3.5 angstrom). Their bandgaps can be widely and linearly tailored from 2.150 (n = 1) to 1.476 eV (n = infinity) with the increase of the inorganic layer number (n). In comparison to the conventional 3D counterparts, they have smaller effective masses, lower exciton energies and larger dielectric constants. Furthermore, the highest power conversion efficiency (PCE) is calculated to be 20.9% (n = 50), evidencing that the quasi-2D DJ CsPbI3 PVSKs could be an excellent candidate for exciting applications in optoelectronic devices.