Robust, Cationic Lead Halide Layered Materials with Efficient Broadband White-Light Emission

Only a selected class of corrugated 2D hybrid lead halide perovskites exhibit broadband white-light emission from self-trapped excitons. Recently, we have discovered ultrastable layered lead halide photoemitters overcoming the stability problems of perovskites, despite in need of deep-UV irradiation to achieve photoluminescence quantum efficiency (PLQE) of over 10%. Herein, we have employed a robust, nonconjugated dicarboxylate ligand to pillar the cationic 1D [PbBr]+ chains. The unique corrugated stacking of [PbBr]+ chains facilitates the structural deformation to form self-trapped excitons, thus enabling an eightfold enhancement of PLQE over our previous reported bilayer bromoplumbate structures. The PLQE of 17.2% is not only among the highest in all of the layered lead halide white-light emitters, but overcoming the problem of our previous photoemitters requires deep-UV LED excitation. In addition, by tuning the stacking mode of the pillaring molecules, the chloride analog successfully incorporates a second photoluminescence center to the broadband emission from self-trapped excitons. The two-component emission strategy in [Pb2Cl2]­[O2C (C6H10)­CO2] offers the intrinsic photoemitter to exhibit tunable cold-to-warm white light upon different excitation lights. The materials demonstrate high chemical robustness over a wide pH range (3–9) and undiminished photoluminescence in air upon UV irradiation for 30 days. Density functional theory calculations indicate that the broadband emission of both materials are induced by the structural deformation of [Pb2X2]2+ (X = Cl/Br) inorganic connectivity, which offers self-trapped electrons from Pb–Pb dimerization and self-trapped holes from Cl–Cl pairing in the excited states