Young's modulus and pressure-induced bandgap changes in CsPbX3 nanoparticles

The nanomechanical properties of lead-halide perovskites are vital for flexible electronics but are challenging to measure directly in individual nanocrystals. Here, we present an original experimental method based on atomic force microscopy for the direct and precise measurement of Young's modulus for single CsPbX3 (X = Br, Cl) nanoparticles via uniaxial compression. The method is based on the measurement of the loading curves followed by their simulations, with a precise reproduction of the nanoparticle and probe tip's shapes. It revealed an apparent size-dependent behavior in the measured Young's moduli, which can be attributed to geometric and instrumental factors of the experiment. Subsequent multi-physical simulation of the experiment revealed more accurate elastic moduli of 16 and 24 GPa for CsPbBr3 and CsPbCl3, respectively. In addition, our calculations based on density functional theory demonstrate that mechanical compression induces bandgap narrowing, particularly strong in CsPbCl3. The study establishes a direct correlation between mechanical stress and electronic structure in perovskite nanomaterials, providing a foundation for the development of compression-resistant and strain-engineered optoelectronic devices.