Solid-State Encapsulation and Color Tuning in Films of Cesium Lead Halide Perovskite Nanocrystals for White Light Generation

Abstract

Perovskite nanocrystals (PNCs) are highly demanding nanomaterials for solid-state lighting applications. A challenge for their exploitation in practical applications is the insufficient ambient and water stability associated with their ionic nature. Here we report a novel route for solid-state encapsulation of films of perovskite nanocrystals (PNCs) through vapor-phase deposition of a thin and hydrophobic layer of fluoroalkyl­trichlorosilanes (FAS). High quality nanoscale crystals of CsPbBr3 were synthesized with well-established colloidal methods and coated on solid substrates. The films of PNCs were then subjected to vapor of FAS for short durations of time (<60 s) in ambient atmosphere, resulting in deposition of a thin (<20 nm) hydrophobic layer. Besides providing a barrier for water and humidity, the vapor-phase deposition of FAS was accompanied by the blue shift of the emission wavelength of the PNCs. The color shift results from the partial exchange of Br with Cl anions, which emerge during the self-hydrolysis of the silane molecules. Throughout this process, we demonstrate the enhanced water stability of the films of PNCs and fine tunability of the wavelength in films from 516 nm to 488 nm. The fabrication of a white-light-emitting diode and tunability of the color coordinates with the duration of the FAS deposition were demonstrated. The rapid, scalable, and inexpensive solid-state encapsulation approach shows great promise for films of halide perovskites.

Recent Advances in Ligand Design and Engineering in Lead Halide Perovskite Nanocrystals

“…[ 374 ] For example, fluoroalkyl trichlorosilanes have been added to a pre‐formed perovskite NC films through a vapor phase, rendering the film hydrophobic. [ 375 ] This created a barrier against water and humidity, allowing for enhanced stability compared to uncoated films when exposed to water (PL intensity reduced only 30% following exposure to water for 120 min compared to 80% for the uncoated film). [ 375 ]…”

“…[ 375 ] This created a barrier against water and humidity, allowing for enhanced stability compared to uncoated films when exposed to water (PL intensity reduced only 30% following exposure to water for 120 min compared to 80% for the uncoated film). [ 375 ]…”

Color‐Stable Deep‐Blue Perovskite Light‐Emitting Diodes Based on Organotrichlorosilane Post‐Treatment

“…[21][22][23] For R-SiCl 3 , reports show that its hydrolysis releases HCl, after which R-SiCl 3 crosslinks with itself. The HCl diffuses into the perovskite film and further interacts with the perovskite via halide anion exchange (e.g., Br − in perovskite with Cl − in HCl) to form a mixed halide perovskite, [18,21,24] which can be described by the following equations:…”

Writing chemical patterns using electrospun fibers as nanoscale inkpots for directed assembly of colloidal nanocrystals

“…To make the surface hydrophobic, the silicon substrate was treated with fluoroalkyl silane (FAS), namely tridecafluoro-1,1,2,2-tetrahydrooctyl-trichlorosilane via vapor-phase deposition. 72 For the freshly cleaned surface, the substrate was treated in a UV-ozone chamber to increase the hydrophilicity. We confirmed the extent of modification by measuring the water contact angles (see ESI Fig.…”