Effect of Grain Size on the Fracture Behavior of Organic-Inorganic Halide Perovskite Thin Films for Solar Cells

Organic-inorganic halide perovskite (OIHP) thin films at the heart of the new perovskite solar cells (PSCs) are very brittle, limiting the mechanical reliability of PSCs. Here we show that fine-grained MAPbI(3) (prototypical OIHP) films with grain size (similar to 290 nm) smaller than the typical film thickness (similar to 500 nm) tend to fracture intergranularly, resulting in low toughness (0.41 J.m(-2)). In contrast, MAPbI(3) /substrate interfacial fracture occurs in films with grains larger (similar to 730 nm) than the film thickness, resulting in much higher toughness (1.14 J.m(-2)). Thus, coarse-grained OIHP films are deemed desirable for not only improved PSCs performance and stability but also mechanical reliability. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.