An Effective Strategy for Photoelectric Performance Enhancement of 2D Perovskite via Halogenating Organic Cation: A Theoretical Prediction

Confronted with the challenge of the inappropriate bandgap, there is an urgent need for effective methods to reduce the bandgap of 2D hybrid perovskites (2DHP) to illuminate their applications in optoelectronic devices. Herein, taking (C6H5NH3)(2)PbI4 as an example, an effective way is predicted to modify the electronic structures of 2DHP by halogenating the benzene ring. The structural, electronic, and optical properties of 2DHP with various numbers and types of halogenated functional groups (HFGs) are systematically investigated. The results show that pure (C6H5NH3)(2)PbI4 exhibits a direct bandgap of 2.28 eV, which can be tuned under the action of HFG. It is particularly noteworthy that the bandgap of 2DHP decreases sharply from 2.28 to 1.64 eV after the benzene ring is fully halogenated by Br. The decline of bandgap is mainly attributed to the action of HFG on the band edges of 2DHP. In addition, HFG can effectively enhance the optical properties of 2DHP. It is firmly believed that the findings will be applied to other 2DHP, paving a new way of improving the photoelectric performance and expanding the application of 2DHPs in optoelectronic devices.