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 perovskite devices include 1) CsPbBr₃-poly(ethylene oxide) layer as emissive layer, 2) NiO_x: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 encapsulation layers consist of metal catalyst-free cross-linked polymethylhydrosiloxane and polydimethylsiloxane 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 polydimethylsiloxane layer is required as a mechanical supporting layer. The polymethylhydrosiloxane/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.