Solid Ligand-Assisted Storage of Air-Stable Formamidinium Lead Halide Quantum Dots via Restraining the Highly Dynamic Surface toward Brightly Luminescent Light-Emitting Diodes

Abstract

Although organometal halide perovskites have garnered enormous interest in solar cells, scarce attention has been paid to light-emitting devices using formamidinium lead halide perovskite as the emitting layer. Highly luminescent and air-stable formamidinium lead halide perovskite quantum dots using high-melting-point ligands have been synthesized. Through compositional engineering, the emission spectra are readily tunable over the entire visible spectral region of 409− 817 nm. The photoluminescence of FAPbX 3 nanocrystals has narrow emission line widths of 21−34 nm, high quantum yields of up to 88%, and a photoluminescence lifetime of 54.6−68.6 ns for single halide FAPbBr 3 , which could be stable for several months. We have demonstrated the fabrication of highly efficient formamidinium lead halide perovskite quantum dot-based green-light-emitting diodes with a moderately high luminance of 33993 cd m −2 , current efficiency of 20.3 cd A −1 , and moderately high maximum external quantum efficiency of 4.07%.

Ten‐Gram‐Scale Synthesis of FAPbX3 Perovskite Nanocrystals by a High‐Power Room‐Temperature Ultrasonic‐Assisted Strategy and Their Electroluminescence

“…X‐ray diffraction (XRD) measurement is performed to illuminate the phase structure. Figure 1b shows the XRD patterns of FAPbBr 3 NCs, the two characteristic peaks at around 14.8° and 30.0° are assigned to the (100) and (200) crystal face of cubic FAPbBr 3 phase, which is consistent with the literature reports . Transmission electron microscopy (TEM) displayed in Figure 1c demonstrates prepared FAPbBr 3 NCs have a cubic shape and the uniform size distribution with the average size of ≈12.2 nm.…”

Green Light-Emitting Devices Based on Perovskite CsPbBr3 Quantum Dots

“…To characterize the structures and compositions of CsPbBr 3 QDs, their crystallographic properties and elements are determined by XRD and XPS (Figure 2A ). Generally speaking, the final crystal structure of CsPbX 3 QDs is strongly dependent on the growth temperature (Li Q. et al, 2017 ). Higher temperature (≥130°C) generally leads to a cubic phase while lower temperature (<130°C) results in an orthorhombic phase (Ling et al, 2016 ).…”

“…Kovalenko and co-workers and Li and co-workers have synthesized CsPbX 3 (X = Cl, Br, I) inorganic perovskite QDs, which exhibited QYs as high as 90%, narrow line width and high stability, which make this all-inorganic perovskite family CsPbX 3 (X = Cl, Br, I) promising for both optical and optoelectronic applications (Nedelcu et al, 2015 ; Li et al, 2016 ). Shortly after that, low threshold, color and shape tunable amplified stimulated emission was reported by other groups simultaneously by using hot injection method (Protesescu et al, 2016 ; Li Q. et al, 2017 ). In terms of perovskite based light-emitting devices, external quantum efficiency (EQE) of green perovskite light-emitting diodes (PeLEDs) is notably improved to 14.36% via composition, phase engineering and surface passivation effect that is achieved by coating organic small molecule trioctylphosphine oxide (TOPO) on the perovskite film surface (Yang et al, 2018 ).…”

Highly UV Resistant Inch‐Scale Hybrid Perovskite Quantum Dot Papers

“…[26,[42][43][44][45][46] Because the conventional OA and OLA ligands are weakly bound to the PQD surface, [47] alternative ligands that can produce strong bonding were proposed to replace OA and OLA, and enhanced stability of PQDs were demonstrated. [42][43][44][45][46] However, these achievements were mostly based on colloidal PQDs. During the transformation from colloidal to solid form, the purification process can lead to considerable ligand loss from the PQD surfaces, thus suppressing the stability.…”