Regulation of optical properties in quasi-2D perovskite heterostructures and their application in photodetection

Organic cation engineering emerges as a powerful strategy for tailoring the optical properties of perovskite materials. In this work, we construct a series of quasi-2D (Q-2D) hybrid perovskite films by tuning the ratio of butylammonium bromide (BABr) to CsPbBr3, revealing the intrinsic correlation between structural evolution and optoelectronic properties. Increasing BABr content not only passivates grain boundary defects and boosts luminescence efficiency but also significantly enhances electron–phonon (EP) coupling strength. The improved energy transfer from low-dimensional phases (n = 2, 3) to the 3D phase, combined with stronger EP coupling, effectively increases the two-photon absorption coefficients. Moreover, photodetectors based on higher BABr content films exhibit faster response and improved operational stability, attributed to enhanced carrier transport via gradient energy distribution and defect suppression by organic layers. This work deepens the understanding of Q-2D perovskite optoelectronics and broadens their applicability in next-generation photonic and electronic devices.