Surface modification strategy based on molecular engineering of an organic cation toward spectrally stable deep-blue emission perovskites

Abstract

All-inorganic perovskites (AIP) with three primary color emission are all-important for AIP application in many fields. However, poor spectral stability seriously hinders the development of blue-emission AIP. Here, we achieved stable deep-blue emission by modifying CsPbBr_3−xCl_x with organic cations. The two ligands improve the luminescence properties of CsPbBr_3−xCl_x by reducing surface defects and increasing exciton binding energy. The electrostatic interaction between –NH₃⁺ and Cl⁻ can inhibit the phase separation of CsPbBr_3−xCl_x and improve the spectral stability of CsPbBr_3−xCl_x. Moreover, the modification effect of the ligand is more obviously increased with the stronger positive charge of –NH₃⁺ and the greater amount of –NH₃⁺. Notably, the deep-blue emission (λ_em < 450 nm) CsPbBr₂Cl modified with 4,4′-biphenyltetramine hydrochloride shows strong spectral stability under continuous ultraviolet light. This work suggests the constructive effect of introducing extra –NH₃⁺ in surface ligands and provides a new model and idea for improving the spectral stability of CsPbBr_3−xCl_x with multidentate ligands.