Perovskite light-emitting diodes (PeLEDs) are considered as promising candidates for next-generation solution-processed full-color displays. However, the external quantum efficiencies (EQEs) and operational stabilities of deep-blue (<460 nm) PeLEDs still lag far behind their red and green counterparts. Herein, a rapid crystallization method based on hot-antisolvent bathing is proposed for realization of deep-blue PeLEDs. By promoting immediate removal of the precursor solvent from the wet perovskite films, development of the quasi-two-dimensional (2D) Ruddlesden–Popper perovskite (2D-RPP) crystals with n values >3 is hampered completely, so that phase-pure 2D-RPP films with bandgaps suitable for deep-blue PeLEDs can be obtained successfully. The uniquely developed rapid crystallization method also enables formation of randomly oriented 2D-RPP crystals, thereby improving the transfer and transport kinetics of the charge carriers. Thus, high-performance deep-blue PeLEDs emitting at 437 nm with a peak EQE of 0.63% are successfully demonstrated. The color coordinates are confirmed to be (0.165, 0.044), which match well with the Rec.2020 standard blue gamut and have excellent spectral stability.
Perovskite light-emitting diodes (PeLEDs) are considered as a promising candidate for next-generation solution-processed full-color displays. However, the external quantum efficiency as well as the operational stability of deep-blue (< 460 nm) PeLEDs still lag far behind compared to their red and green counterparts. Herein, the rapid crystallization method based on antisolvent bathing is proposed for trealization deep-blue PeLEDs. By promoting the immediate removal of precursor solvents from the wet perovskite films, the development of the quasi-2D Ruddlesden‒Popper perovskite (2D-RPP) crystals with n value of < 3 was completely hampered, so that phase-pure 2D-RPP films whose bandgap is suitable for deep-blue PeLEDs were successfully obtained.
Nanosecond laser ablation of polyvinylpyrrolidone (PVP) protected silver nanoparticle (20 nm diameter) film is studied using a frequency doubled Nd:YAG nanosecond laser (532 nm wavelength, 6 ns full width half maximum pulse width). In the sintered silver nanoparticle film, absorbed light energy conducts well through the sintered porous structure, resulting in ablation craters of a porous dome shape or crown shape depending on the irradiation fluence due to the sudden vaporization of the PVP. In the unsintered silver nanoparticle film, the ablation crater with a clean edge profile is formed and many coalesced nanoparticles of 50 to 100 nm in size are observed inside the ablation crater. These results and an order of magnitude analysis indicate that the absorbed thermal energy is confined within the nanoparticles, causing melting of nanoparticles and their coalescence to larger agglomerates, which are removed following melting and subsequent partial vaporization.
Ablation of metal nanoparticle film using frequency doubled Nd:YAG nanosecond laser is explored to apply for
trimming drop on demand (DOD) inkjet printed electrical micro-conductor for flexible electronics. While elevated rim
structure due to expulsion of molten pool is observed in sintered nanoparticle film, the ablation of unsintered
nanoparticle film results in a Gaussian-shaped ablation profile, so that a clean precise patterning is possible. In addition,
the ablation fluence threshold of unsintered metal nanoparticle film is at least ten times lower than that of a
corresponding metal film. Therefore, by using nanosecond laser ablation, inkjet printed metal nanoparticles compatible
for flexible polymer can be patterned efficiently with a high resolution.
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