Lead-free bilayer heterometallic halide perovskite with reversible phase transition and photoluminescence properties

The layered heterometallic halide perovskites, as a newly explored material, have attracted great scientific attention. As one of the representatives of perovskite, lead-free or lead-substituted perovskite materials are widely applied in photovoltaic, sensors, catalysis, detectors and other fields. Therefore, it is urgent to carry out more systematic exploration and expand applicable preresearch, so as to make more interesting discoveries in this new hot spot. As an interesting candidate, heterometallic compounds will introduce more structural adjustability and novel physical properties, which is the main feature to be selected as the research hotspot. Here, we reported a lead-free bilayer heterometallic Ruddlesden-Popper (RP) type perovskite, [(MACH)2CsAgBiBr7] (MACH = cyclohexanemethylamine), which possesses a reversible phase transition at 379.6 K/375.1 K during heating-cooling cycle. Besides, it exhibits reddish-brown light emission under 365 nm, meanwhile, CIE chromaticity coordinate is (0.32, 0.45) on the yellow side and correlated color temperature is about 6000 K. Moreover, both the experimental data and theoretical calculation results suggest that [(MACH)2CsAgBiBr7] shows indirect semiconducting characteristics. In summary, this work will inspire the design of lead-free heterometallic perovskite materials for the application of sensors and light-emitting diodes (LEDs) fields.