Intrinsic Broadband White-Light Emission from Ultrastable, Cationic Lead Halide Layered Materials

We report a family of cationic lead halide layered materials, formulated as [Pb2X2](2+)[-O2C(CH)(2)CO2-] (X=F, Cl, Br), exhibiting pronounced broadband white-light emission in bulk form. These well-defined PbX-based structures achieve an external quantum efficiency as high as 11.8%, which is comparable to the highest reported value (ca.9%) for broadband phosphors based on layered organolead halide perovskites. More importantly, our cationic materials are ultrastable lead halide materials, which overcome the air/moisture-sensitivity problems of lead perovskites. In contrast to the perovskites and other bulk emitters, the white-light emission intensity of our materials remains undiminished after continuous UV irradiation for 30 days under atmospheric conditions (ca.60% relative humidity). Our mechanistic studies confirm that the broadband emission is ascribed to short-range electron-phonon coupling in the strongly deformable lattice and generated self-trapped carriers.