Influence of double layer PMHS/PDMS encapsulation on CsPbBr3 PeLEC properties in high humidity conditions

In this paper we describe a new method to improve properties of a perovskite light-emitting electrochemical cell (PeLEC) by double layer polymer encapsulation. Our per-ovskite devices include 1) CsPbBr3-poly(ethylene oxide) layer as emissive layer, 2) NiOx:Cu nanoparticles layer as hole transport layer, 3) a transparent single wall carbon nanotubes as an electrode of the structure and 4) a double layer encapsulation polymer layers. These encap-sulation layers consist of metal catalyst-free cross-linked polymethylhydrosiloxane and poly-dimethylsiloxane Sylgard 184. After 168 hours of aging in 80% relative humidity conditions an increase in luminance and in photo luminance quantum yield of our devices was detected. Our encapsulation provides optimal exposure of water vapor on perovskite material, which improves device properties by partial phase transition of CsPbBr3 to Cs4PbBr6, which has been confirmed by X-ray diffraction method. The Cs4PbBr6 passivate CsPbBr3 crystals and then the polymethylhydrosiloxane layer does not allow agglomeration of perovskite grains. The poly-dimethylsiloxane layer is required as a mechanical supporting layer. The polymethylhydrosilox-ane/polydimethylsiloxane encapsulation of perovskite devices reveals a promising new way of development of flexible and stretchable perovskite light-emitting devices, which can work in extreme humid conditions.