Exciton-Phonon Coupling and Vibronic Emission Structure in 2D Perovskite Thin Films with Naphthylmethylamine Spacers

Exciton-phonon coupling (EPC) plays a key role in the photophysics of 2D hybrid perovskites (2DHPs) and greatly affects their optoelectronic properties. Compared with excitons coupled with phonons of metal halide lattices, our knowledge of EPC with phonons of organic cations is still limited. In this work, we conducted systematic temperature-dependent photoluminescence (PL) analysis on I- and Br-based 2DHPs with 1-NMA or 2-NMA cations (NMA = naphthylmethylamine). For I-based (1-NMA)(2)PbI4 and (2-NMA)(2)PbI4, moderate EPC with a Pb-I lattice phonon (similar to 20 meV) was observed. Intriguingly, Br-based 2DHPs exhibit strong cation-dependent PL spectra, i.e., (1-NMA)(2)PbBr4 exhibits a vibronic structure extending to the low-energy side, while a hot-exciton vibronic structure extending to the high-energy side was observed for (2-NMA)(2)PbBr4. The latter was attributed to excitons coupled with a similar to 50 meV phonon residing on 2-NMA cations. Our work revealed the critical role of both organic cations and halide anions in EPC in 2DHPs, which may provide inspiration for designing high-performance 2DHP optoelectronic devices.

Automated summary

The exciton-phonon coupling in 2D hybrid perovskites are crucial for their optoelectronic properties, however, limited knowledge is available for the coupling between excitons and phonons of organic cations. This study systematically analyzed the temperature-dependent photoluminescence of I- and Br-based 2DHPs with different cations, revealing the critical role of organic cations and halide anions in exciton-phonon coupling and providing inspiration for designing high-performance 2DHP optoelectronic devices.