Abstract
Large-area light-emitting diodes (LEDs) fabricated by mass-production techniques are needed for low-cost flat-panel lighting. Nevertheless, it is still challenging to fabricate efficient large-area LEDs using organic small molecules (OLEDs), quantum dots (QLEDs), polymers (PLEDs), and recently-developed hybrid perovskites (PeLEDs) due to difficulties controlling film uniformity. To that end, we report sol-gel engineering of low-temperature blade-coated methylammonium lead iodide (MAPbI3) perovskite films. The precipitation, gelation, aging, and phase transformation stages are dramatically shortened by using a diluted, organoammonium-excessed precursor, resulting in ultra-flat large-area films (54 cm2) with roughness reaching 1 nm. The external quantum efficiency of doctor-bladed PeLEDs reaches 16.1%, higher than that of best-performing blade-coated OLEDs, QLEDs, and PLEDs. Furthermore, benefitting from the throughput of the blade-coating process and cheap materials, the expected cost of the emissive layer is projected to be as low as 0.02 cents per cm2, emphasizing its application potential.
Highlights
Large-area light-emitting diodes (LEDs) fabricated by mass-production techniques are needed for low-cost flat-panel lighting
We report highly efficient perovskite LEDs (PeLEDs) fabricated by a robust blade-coating approach at a low temperature of 50 °C
In order to figure out the origin of improved film morphology using very dilute precursor solutions and with excess fluorophenylmethylammonium iodide (FPMAI), we examined the film-forming process using an optical microscope (Supplementary Movies 1–4)
Summary
Large-area light-emitting diodes (LEDs) fabricated by mass-production techniques are needed for low-cost flat-panel lighting. The large-area, blade-coated films show great uniformity in terms of thickness, roughness, and optoelectronic properties. It should be noted that the blade-coating speed, temperature, and the N2 knife pressure affect the film morphology dramatically
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