High Quality Inkjet Printed‐Emissive Nanocrystalline Perovskite CsPbBr₃ Layers for Color Conversion Layer and LEDs Applications

Abstract

Metal halide perovskites (MHPs) have shown outstanding optical emissive properties and can be employed in several optoelectronics devices. In contrast with materials of well‐established technologies, which are prone to degradation or require expensive processes, MHPs can be obtained by solution processing methods and increase stability. Inkjet printing is proposed as an industrial friendly technique to deposit MHPs. The inks have been developed from colloidal CsPbBr3 nanocrystals and printing procedures that allow the deposition of thin layers with intense green emission. High emissive printed layers are assured by carrying out thermal annealing in vacuum oven, which is demonstrated to promote compact layers with low roughness, corroborated by SEM and AFM. XRD measurements show CsPbBr3 crystalline layers with cubic symmetry and XPS provides insight into the stoichiometric composition and local bonding. Optical properties of inkjet‐printed CsPbBr3 films have been analyzed by UV–vis absorbance and photoluminescence (PL), to extract the bandgap energy and photoluminescence quantum yield (PLQY). CsPbBr3 printed layers emit at 524 nm with a narrow emission (FWHM ≈ 15 nm), exhibiting a PLQY up to 20%. These results enabled the large‐scale fabrication by inkjet printing of CsPbBr3 color conversion layers (CCLs) and pave the way for flexible LEDs.

Fabrication of Perovskite Nanocrystal Light-Emitting Diodes via Inkjet Printing with High-Temperature Annealing

“…Metal halide perovskite nanocrystals (NCs) have attracted attention as promising materials for solution-processed light-emitting diodes (LEDs) because of their near-unity photoluminescence quantum yield (PLQY) and high color purity over the entire visible-to-near-infrared range. − The external quantum efficiency (EQE) of perovskite NC-LEDs has improved by up to 23.4% in the past few years because of the development of various types of surface passivation techniques, structural engineering, and device structure optimization. − Inkjet printing is a promising solution-processed technique for organic light-emitting diodes (OLEDs) − and quantum-dot light-emitting diodes (QLEDs) − because of the possibilities of using mask-free methods and micropatterning with efficient ink utilization. In recent years, inkjet-printed perovskite LEDs have been fabricated using precursor solutions for perovskite films − and colloidal perovskite NCs inks. − Precursor solutions commonly consist of metal halide precursors, ammonium halides, and polymer binders, which are dissolved in a polar solvent, dimethyl sulfoxide (DMSO). The precursor materials are recrystallized to form a perovskite structure after solvent evaporation .…”

2D PEA2SnI4 Inkjet-Printed Halide Perovskite LEDs on Rigid and Flexible Substrates

“…It does not offer spatial resolution for the deposition of multiple LEDs in large areas, and a major amount of the precursors is wasted. 13 , 14 In contrast, inkjet printing is an emerging technology suitable to achieve smooth, uniform, and pinhole free thin films 15 that can be exploited to produce low-cost, large area, and even foldable devices and arrays. 16 Inkjet printing is believed to be the most feasible tool for patterning full color QD-LED displays for mass production.…”

“…Beyond materials demands, development of Pb-free PeLEDs will require industrial friendly fabrication methods, since spin-coating, the usual lab approach for film deposition, is not an appropriate technique for upscaling. It does not offer spatial resolution for the deposition of multiple LEDs in large areas, and a major amount of the precursors is wasted. , In contrast, inkjet printing is an emerging technology suitable to achieve smooth, uniform, and pinhole free thin films that can be exploited to produce low-cost, large area, and even foldable devices and arrays . Inkjet printing is believed to be the most feasible tool for patterning full color QD-LED displays for mass production …”

Progress in Color Conversion Technology for Micro‐LED

“…After selecting the right ink, high-resolution printing can be achieved. [117][118][119][120][121][122][123][124][125][126][127][128] Therefore, the CCL can be printed on each sub-pixel to display a full-color Micro-LED display. [104,129] In 2015, the H. C. Kuo research group used aerosol spraying technology to deposit colloidal QDs CdSe/ZnS on GaN chips, as shown in Figure 7a, showing a Micro-LED with independently addressable RGB pixels array, the display size is 5 mm × 5 mm, the resolution is 128 × 128, among which the size of a single chip is 35 µm, and the interval is 5 µm, [63] as shown in Figure 7b.…”