Tunable Deep-Red Electroluminescence From Flexible Quasi-2D Perovskites Light-Emitting Diodes

In this letter, we synthesize and characterize a new series of organic/inorganic hybrid quasi-2D perovskites PEA 2 (FA) n–1 Pb n I 3n+1 ( $n = 2, 3, 5$ ). The quantum well thickness of perovskites could be adjusted by regulating the crystal structure, which resulted in a tunable bandgap and emission spectra. The deep-red emissions from the flexible light-emitting diodes have been successfully achieved. The optimal device presents a maximum luminance of 212 cd/m 2 , a maximum current efficiency of 0.44 cd/A, and a maximum external quantum efficiency of 0.148% with an electroluminescent spectrum peak of 720 nm and the corresponding CIE coordinates of (0.691, 0.291).