Molecule Dipole Engineering to Manipulate Exciton−Phonon Coupling in 2D Perovskites toward Efficient Photodetectors

ABSTRACT 2D hybrid perovskites have sparked intense attention in optoelectronic fields owing to their fascinating excitonic properties and improved structural stability. The exciton‐phonon coupling, which governs charge carrier transport, significantly influences optoelectronic performance. Herein, we exert molecule dipole engineering to effectively govern the exciton‐phonon coupling in 2D perovskites, as achieved by the incorporation of polar 3‐aminopropionitrile (3‐APN) spacer. It is shown that the polarization of the 3‐APN spacer enhances the dielectric screening effect, thus reducing the exciton binding energy down to 60 meV. Moreover, the high electron localization around ‐CN of 3‐APN spacer facilitates strong hydrogen bonding within organic bilayers and reconstructs the organic–inorganic hydrogen bonding interactions, leading to strengthened lattice rigidity. This modification suppresses lattice vibrations, thereby diminishing the exciton‐phonon coupling. These effects collectively result in prolonged carrier lifetime, enlarged carrier mobility, and extended carrier diffusion length of ∼ 50 µm at the device level. Importantly, (3‐APN) 2 PbI 4 single crystal photodetector achieves outstanding responsivity of 1.05 AW −1 and detectivity of 4.23 × 10 12 Jones. This work offers a feasible method to modulate the exciton‐phonon coupling in 2D perovskites by employing bifunctional spacers with large dipole moment.