Mixing Organic Cations in 2D Perovskites—Tuning Photoluminescence and Phase Transition Temperatures

Blending cations and anions in hybrid perovskites has emerged as a powerful strategy to tune optoelectronic properties. Although blending inorganic cations and halides is a standard practice to tune both the absorption and emission of these materials, blending organic cations in two-dimensional (2D) perovskites is rarely pursued. In this work, we use a homebuilt high-throughput robotic platform to fabricate and characterize 2D perovskite thin films with mixed organic cations. By blending alkylammonium cations of different lengths, we demonstrate that we can precisely and continuously tune the phase transition temperature of 2D perovskites. When blending more chemically complex cations, we show that these cations either phase separate or mix. We characterize the arrangement of organic cations using nanoscale infrared imaging with photoinduced force microscopy (PiFM) and demonstrate mixed organic cation systems that allow us to continuously tune the emission wavelength of 2D perovskites. Our aim is to establish organic cation mixing as a powerful way to tune both the optoelectronic and thermodynamic properties of 2D perovskites.