Suppressing Growth Strategy on Synthesizing Stable and High-Quality Blue-Emitting CsPbBr3 Quantum Dots

Abstract

In recent years, deep-blue perovskite light-emitting diodes (PeLEDs) based on ultra-small CsPbBr3 quantum dots (QDs) have attracted increased attention. However, ultra-small CsPbBr3 QDs tend to have more defects and more nonradiative processes because of their ultrafast nucleation and growth rates. How to suppress the nucleation and growth rate is an important issue for developing deep-blue emitting CsPbBr3 QDs with high performance. Herein, a modified hot-injection method (MM) is designed for suppressing the growth process of CsPbBr3. The ligands of oleic acid (OA) and oleylamine (OAm) are employed instead of octadecene (ODE) as the solution, and as a result, the strong confined and high-quality CsPbBr3 QDs (∼4.45 nm) are obtained, presenting strong deep-blue emission (≈465 nm) with a photoluminescence quantum yield (PLQY) of 95%, an average lifetime of 8.84 ns, and a large exciton binding energy of 268.7 meV, which can maintain blue emission over 30 days under atmospheric conditions. Compared with the CsPbBr3 nanocubes (NCs) obtained by the common hot-injection method (CM), the CsPbBr3 QDs obtained by MM have fewer defects and trap states, resulting in less nonradiative processes. In addition, the fabricated PeLEDs based on the above CsPbBr3 QDs show deep-blue emission with Commission Internationale de l’Eclairage (CIE) color coordinates of (0.129 and 0.074), which is better than the blue standard of the National Television Standards Committee (NTSC). Evidently, this work provides a way to synthesize ultra-small CsPbBr3 QDs and also reflects the important influence of the reaction solvent on perovskite synthesis.