Failure Mechanisms of Stretchable Perovskite Light-Emitting Devices under Monotonic and Cyclic Deformations

This paper presents the results of experimental and analytical studies of the failure mechanisms of stretchable perovskite light-emitting devices (PeLEDs). The multilayered PeLED structures consist of an anodic layer of poly(3,4-ethylenedioxythiophene):polystyrene-sulfonate (PEDOT:PSS), an emissive layer of methylammonium lead bromide (MAPbBr(3)), and a eutectic gallium-indium (EGaIn) cathodic layer, which are deposited onto treated polydimethylsiloxane substrates. The intrinsically nonstretchable MAPbBr(3) and PEDOT:PSS are modified with poly(ethylene oxide). The failure mechanisms of the layered stretchable PeLED structures are then investigated under monotonic and cyclic deformations. The optical and scanning electron microscopy images show the deflection and propagation of cracks and wrinkles under applied strains. Cracking of perovskite crystal and debonding of films are also observed with increased cyclic deformation. The effects of the failure mechanisms on the optoelectronic properties of the devices are then studied. The in situ measured transmittance of the PEDOT:PSS (approximate to 75%) reduces with increasing uniaxial strain, and then is increased close to its initial value when the strain is released. The turn-on voltage of the device increases with increasing number of cycles between 50 and 1000 cycles at 20% strain level. The fatigue lifetimes of the PeLED structures are used to explain the design of stretchable perovskite devices.