All-Inorganic CsPbI3 Perovskite Phase-Stabilized by Poly(ethylene oxide) for Red-Light-Emitting Diodes

Despite the excellent photoelectronic properties of the all-inorganic cesium lead iodide (CsPbI3) perovskite, which does not contain volatile and hygroscopic organic components, only a few CsPbI3 devices are developed mainly owing to the frequent formation of an undesirable yellow -phase at room temperature. Herein, it is demonstrated that a small quantity of poly(ethylene oxide) (PEO) added to the precursor solution effectively inhibits the formation of the yellow alpha-phase during film preparation, and promotes the development of a black alpha-phase at a low crystallization temperature. A systematic study reveals that a thin, dense, pinhole-free CsPbI3 film is produced in the alpha-phase and is stabilized with PEO that effectively reduces the grain size during crystallization. A thin alpha-phase CsPbI3 film with excellent photoluminescence is successfully employed in a light-emitting diode with an inverted configuration of glass substrate/indium tin oxide/zinc oxide/poly(ethyleneimine)/-CsPbI3/poly(4-butylphenyl-diphenyl-amine)/WO3/Al, yielding the characteristic red emission of the perovskite film at 695 nm with brightness, external quantum efficiency, and emission band width of approximate to 101 cd m(-2), 1.12%, and 32 nm, respectively.