Mechanical properties of organic–inorganic halide perovskites, CH3NH3PbX3 (X = I, Br and Cl), by nanoindentation†
We report an experimental study of the mechanical properties of the organic–inorganic halide perovskites, CH3NH3PbX3 (X = I, Br and Cl). Nanoidentation on single crystals was used to obtain Young's moduli (E) and hardnesses (H) of this class of hybrid materials, which have attracted considerable attention for photovoltaic applications. The measured Young's moduli of this family lie in the range 10–20 GPa and a trend of ECl > EBr > EI is observed. The physical properties are consistent with the underlying crystal structure. In particular, the results are in reasonable agreement with recent calculations using density functional theory and align with expectations based upon bond energy, packing, and hydrogen-bonding considerations. The anisotropy in these systems is quite small, with E100 > E110 for the cubic bromide and chloride cases and E112 ≈ E100 for the tetragonal iodide perovskites. Interestingly, CH3NH3PbI3 is harder than the Br- and Cl-based perovskites.