Dipole Regulation Ultrahigh-Oriented Two-Dimensional Perovskite Films for UV-Excited Secure Quick Response Codes

The widespread application of quick response (QR) codes has brought data security issues to the forefront, largely due to the ease of data accessibility. In this study, we designed a two-dimensional perovskite material, (FPA)2PbBr4 (FPA = (R)-1-(4-fluorophenyl)ethylamine), to enhance data security by increasing the retrieval threshold of QR codes. This material exhibits little absorption in the visible light spectrum, with an abrupt absorption edge at 402 nm. Notably, by introducing an F– anion into the spacer and inducing protonation, the dipole moment of the spacer from 1.26 to 11.03 D facilitates rapid self-assembly crystallization of the two-dimensional (2D) perovskite. More importantly, we obtained (FPA)2PbBr4 crystal films with a high crystal orientation (001) by solution spin coating. The encoded QR code base on the high-orientated 2D perovskite film could only be read under 385 nm UV light irradiation, making it unreadable under normal conditions and thereby enhancing data security. This study provides an innovative approach to data security concerns in QR code technology.