Structurally Stable and Highly Enhanced Luminescent Perovskite Based on Quasi-Two-Dimensional Structures upon Addition of Guanidinium Cations
Wonhee Cha, Hyowon Han, Yongseok Hong, Gakhyun Kim, Cheolmin Park, Dongho Kim
Abstract
Lead halide perovskites have received much attention as light emitting materials owing to their excellent photoelectronic properties. Despite their high efficiency as light-emitting diodes (LEDs), only a few lead bromide perovskite (APbBr3)-based devices have been developed due to their low stabilities and/or the formation of undesirable phases under ambient condition. This work demonstrates that the addition of a small quantity of guanidinium (GUA) A-site cations into an all-inorganic CsPbBr3 perovskite framework leads to the formation of multidimensional perovskites, with enhanced photoluminescence efficiency due to charge carrier funneling and a pinhole-free surface morphology. All-inorganic 3D CsPbBr3 perovskite films and GUA-incorporated multidimensional quasi-2D films are employed in the fabrication of green LED devices with an inverted structure of glass substrate/indium tin oxide (ITO)/zinc oxide (ZnO)/poly(ethylenimine) (PEI)/perovskite/poly(9-vinylcarbazole) (PVK)/WO3/Al. With the addition of GUA A-site cations, the LEDs based on GUA-incorporated perovskite thin films exhibited much higher brightness of ∼10000 cd m–2 and current efficiency of 9.4 cd A–1 compared to those of Cs-only perovskite thin film LEDs (∼400 cd m–2 and 0.2 Cd A–1, respectively).