Effect of silica encapsulation on the stability and photoluminescence emission of FAPbI3 nanocrystals for white-light-emitting perovskite diodes

The α-FAPbI 3 perovskite nanocrystals exhibit interesting optical properties, which make them attractive for versatile optoelectronic applications; however, the spontaneous phase transformation to the non-perovskite phase (δ-FAPbI 3 ) in humid conditions requires a new strategy to improve the phase stability of the material. We employed 3-Aminopropyl triethoxysilane (APTES)-assisted reprecipitation and sol-gel methods at ambient temperature to prepare stable α-FAPbI 3 nanocrystals embedded in a silica matrix. Transmission electron microscopy (TEM) and X-ray diffraction analysis determined that ultrafine perovskite nanocrystals (11.5 ± 3 nm) were uniformly distributed in a silica matrix. Investigations of the optical properties of the synthesized materials revealed that about 94% of the photoluminescence (PL) emission of silica-encapsulated FAPbI 3 nanocrystals was preserved under humid conditions (60%) after at least a month, while the PL emission of untreated FAPbI 3 was significantly decayed after few days. The thermal analysis also determined that the thermal stability of FAPbI 3 nanocrystals was improved by silica encapsulation. The red-emitting silica-encapsulated FAPbI 3 nanocrystals with a wavelength of 720 nm were used to fabricate white light-emitting diodes (LEDs) in a vertical structure consisting of a blue-chip, PMMA/CsPbBr 3 QDs, and PMMA/FAPbI 3 -SiO 2 QDs. Stable perovskite-based white LEDs with a color gamut of 144% NTSC were fabricated, which was better than many phosphor-based and perovskite-based LEDs. The synthesized composite perovskite nanocrystals could be used for next-generation optoelectronic devices. • Synthesis of silica-encapsulated FAPbI 3 quantum dots at ambient temperature by a combined LARP and sol-gel process. • Minor PL intensity loss in the humidified atmosphere after few months. • WLEDs with a high color gamut of 144% NTSC. • A pure red LED with coordination (0.729, 0.270).