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.