Bright and Effectual Perovskite Light-Emitting Electrochemical Cells Leveraging Ionic Additives

Perovskite light-emitting diodes (PeLEDs) have drawn considerable attention for their favorable optoelectronic properties. Perovskite light-emitting electrochemical cells (PeLECs)—devices that utilize mobile ions—have recently been reported but have yet to reach the performance of the best PeLEDs. We leveraged a poly(ethylene oxide) electrolyte and a lithium salt in CsPbBr 3 thin films to produce PeLECs of improved brightness and efficiency. In particular, we found that a single-layer PeLEC from CsPbBr 3:PEO:LiPF 6 with 0.5 wt % LiPF 6 produced bright (∼15000 cd/m 2 ) electroluminescence of improved efficiency (3.0 Lm/W). To understand this improved performance among PeLECs, we characterized these perovskite thin films with photoluminescence (PL) spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). These studies revealed that this optimal LiPF 6 concentration improves electrical double-layer formation, reduces the occurrence of voids, charge traps, and pinholes, and increases grain size and packing density.