Quasi-2D Hybrid Organic-Inorganic Perovskites: DFT Modeling Approach

Hybrid organic-inorganic perovskites (HOIPs) have developed to become highly promising solution-processable direct-bandgap semiconductors, which have exhibited high solar conversion efficiencies due to their outstanding charge carrier mobilities. HOIPs exhibit superior optical properties due to their relatively high photoluminescence quantum efficiency and high brightness emission. Furthermore, HOIPs have garnered much interest due to their tunable bandgaps; which are controlled by modifying the dimensionality and composition of the perovskites. In this study, we utilize DFT methods to investigate the emission of HOIPs in order to achieve reliable tunability of bandgap. We investigate quasi-2D perovskites which are considered to form multiple quantum wells, in which the inorganic layers act as wells and the bulky organic spacers as barriers. It is well known that the bandgap of these layered perovskites can be tuned by varying the “quantum well” thickness (corresponding to n in Aʹ2An-1BnX3n+1). While it has been shown that the size of the organic cations occupying the cuboctahedral cavity of 3D perovskites indirectly affect bandgap by altering B-X orbital overlap through octahedral distortions, the effect of the spacer size (in the interlayer region) has not been fully understood in 2D perovskites. In this study, we investigate the effects of aliphatic and aromatic spacers on the bandgap and formation energies of HOIPs. Furthermore, we characterize a correlation between the steric size of the spacer cation and band gap, which is a key characteristic for the design of optoelectronics. Overall, we find that the choice of the spacer cation can play a crucial role in tuning the emission of perovskite light-emitting diodes.