Control of morphology and grain size for efficient perovskite light-emitting diodes

Abstract

Nowadays paradigm of display industries have shifted flat screen into flexible or curved screen with emerging of plastic organic light emitting diodes (POLED). In spite of the obvious strength of POLED, our next assignments are focusing on realize both high performance and low cost display. From this perspective, Organic-inorganic hybrid perovskite is promising emitting material as new generation emitter for light emitting diodes (LED) owing to their high color purity, easy band gap tunable structure, quantum well structure formation with brilliant charge carrier mobility and scalable soluble processing at low temperature. However, intrinsic delimitation of perovskite that weak exciton binding energy, long exciton diffusion length, humidity and thermal stability, etc. should be overcome for convincing light emitting material.

In this work, we research systematically methodology on crystallization with methyl-ammonium lead bromide ($MAPbBr_3$) perovskite in order for high functional emitting layer, define the perovskite film morphology and device performance of the organic-inorganic hybrid perovskite LED (PeLED) by various solvent engineering method and post thermal treatment. We demonstrate precisely controllable crystallization of PeLEDs by utilizing beam-damage-free near infrared (NIR) diode laser. In result, we have found out critical relationship among the crystal grain size and thin film morphology, efficiency of PeLEDs are established while attaining the device performance of 0.95 cd$A^{-1}$ efficiency and 1784 cd$m^{-2}$.

Laser crystallization is a convincing methodology for material processing owing to its intrinsic competitiveness such as highly rapid heating and cooling, low temperature continuous processing, compatibility with flexible device process, scalability and area selectivity. While research demand for the commercialization of perovskite diodes is growing, large area film deposition methods with high speed and process continuity are becoming more significant. A laser crystallization method which is available for large area/flexible devices at low-temperature with process continuity is a significant achievement for eventual commercial success.