Enhancing and Extinguishing the Different Emission Features of 2D (EA_1−xFA_x)₄Pb₃Br₁₀ Perovskite Films

Abstract 2D hybrid perovskites are attractive for optoelectronic devices. In thin films, the color of optical emission and the texture of crystalline domains are often difficult to control. Here, a method for extinguishing or enhancing different emission features is demonstrated for the family of 2D Ruddlesden–Popper perovskites (EA_1−xFA_x)₄Pb₃Br₁₀ (EA = ethylammonium, FA = formamidinium). When grown from aqueous hydrobromic acid, crystals of (EA_1−xFA_x)₄Pb₃Br₁₀ retain all the emission features of their parent compound, (EA)₄Pb₃Br₁₀. Surprisingly, when grown from dimethylformamide (DMF), an emission feature, likely self‐trapped exciton (STE), near 2.7 eV is missing. Extinction of this feature is correlated with DMF being incorporated between the 2D Pb‐Br sheets, forming (EA_1−xFA_x)₄Pb₃Br₁₀∙(DMF)_y. Without FA, films grown from DMF form (EA)₄Pb₃Br₁₀, retain little solvent, and have strong emission near 2.7 eV. Slowing the kinetics of film growth strengthens a different emission feature, likely a different type of STE, which is much broader and present in all compositions. Films of (EA_1−xFA_x)₄Pb₃Br₁₀∙(DMF)_y have large, micron‐sized domains and homogeneous orientation of the semiconducting sheets, resulting in low electronic disorder near the absorption edge. The ability to selectively strengthen or extinguish different emission features in films of (EA_1−xFA_x)₄Pb₃Br₁₀∙(DMF)_y reveals a pathway to tune the emission color in these compounds.