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This paper presents the results of a combined experimental and computational study of the mechanisms of blister formation, and their effects on the degradation of organic light emitting devices (OLEDs). Blister formation is attributed to the effects of thermally induced mismatch stresses associated with applied bias. These result in interfacial cracking phenomena that are affected by the solvents that are used in OLED fabrication. The OLEDs are first fabricated using an electron transport layer of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) deposited on an active layer made from solutions of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] dissolved in different solvents (toluene, chloroform, and chlorobenzene). The formation of blisters and degradation is then studied under applied bias for devices fabricated using different solvents (toluene, chloroform, and chlorobenzene) and emissive layer thicknesses. The underlying layer mechanical properties are then incorporated into interfacial fracture mechanic models that explain the formation of blisters that degrade the performance of OLED structures.

This paper uses a combination of experiments and theory to study the effects of annealing temperature on the mechanical properties of hybrid organic–inorganic perovskites (HOIPs). We examined the mechanical (hardness and Young’s modulus), microstructural, and surface topography properties of the HOIP film at different annealing temperatures ranging from 80 to 170 °C. A mechanism-based strain gradient (MSG) theory is used to explain indentation size effects in films at different annealing temperatures. Intrinsic film yield strengths and hardness values (deduced from the MSG theory) are then shown to exhibit a Hall–Petch dependence on the inverse square root of the average grain size. The implications of the results are then discussed for the design of mechanically robust perovskite solar cells.