Bending Fracture Behavior and Chemical Degradation of Polymer-Passivated Flexible Organic Lead Halide Perovskite Thin Films

Although halide perovskites have significant potential for flexible electronic and optoelectronic devices, detailed bending mechanical behavior of encapsulated halide films has not been reported yet. Herein, we report the enhanced bending fracture behavior of flexible methylammonium lead triiodide (MAPbI3) thin films passivated with two selected polymer over-layers of polystyrene (PS) and poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The substantial mechanical enhancements were evident from the estimated fracture parameters, including critical strain, fracture energy, and film strength. For example, a highly concentrated PS passivation layer with ~51 nm thickness exhibited the largest fracture energy of 60.4 Jm-2 and the highest film strength of 299.9 MPa, which correspond respectively to ~96% and ~40% improvements compared to those of the non-passivated reference. Effects of the chemical passivation was also confirmed by chasing phase-dissolution of the perovskite with correlative changes of Hall-electrical properties.