Tuning Napththalenediimide Cations for Incorporation into Ruddlesden–Popper-Type Hybrid Perovskites

Layered hybrid organic–inorganic perovskite (LHOIP) materials constructed with low-band-gap chromophore-based organic spacer cations are an emerging class of materials that promise unique tunability of their optoelectronic properties. However, the large size of such chromophore-based spacer cations challenges their incorporation into a layered perovskite structure and requires further insight into the layered perovskite phase formation mechanism. Herein, we report the preparation and incorporation of asymmetric naphthalenediimide (NDI) spacer chromophore cations with different amine-bearing alkyl linker chains into thin films of LHOIPs. Using in situ UV–vis spectroscopic kinetic studies of the quantum well formation, we show that shorter linker chain lengths require higher annealing temperatures to form the LHOIP structure. Avrami analysis of the layered perovskite formation shows a larger Avrami coefficient (n = 3.64) for short linker chain-bearing cations compared to that for longer alkyl chain-bearing cations (n = 2.43), suggesting an evolution from three-dimensional to quasi-two-dimensional crystal growth with increasing linker chain length. Additionally, transient absorption spectroscopy and broad-band fluorescent upconversion spectroscopy indicate fast photoinduced charge transfer from the inorganic layer to the electron-accepting NDI-spacer cation.