Strain engineering is one promising strategy which has been proposed to improve the stability of metal halide perovskite solar cells, a key obstacle which must be overcome before they can be widely deployed commercially. However, even nominally similar perovskites under near-identical strain conditions can display very different responses to applied stress. Understanding how strain impacts the optoelectronic properties of perovskites can be advantageous for device makers to exploit these impacts in device design. Probing mechanical strain directly can provide a clearer insight into the impact of strain on these materials. In this work, we investigate the effects of in-situ externally applied tensile strain on both the structural and optical properties of CsPbBr3 microcrystals using a piezo-electric strain stage.

We mapped the structural evolution of the crystals under unstrained and strained conditions at Diamond Light Source using nano X-ray diffraction. By measuring the shifts in interplanar spacings as the samples undergo strain, we produced maps showing the strain distribution across the crystal for different crystallographic planes. This revealed spatially heterogeneous strain distributions across individual crystals. We also probed the latency of the sample response to applied strain and it is demonstrated how the shift in interplanar spacing occurs at different temporal rates across one crystal.

Optical maps were also collected of the samples under the strain conditions to investigate how strain impacts the charge carrier dynamics within the microcrystals. A time-resolved hyperspectral microscopy system was developed to be able to observe the photoluminescence with sub-nanosecond temporal resolution and across a wide spectral range. This developed system can be used to achieve up to eight orders of dynamic range for temporal measurements, meaning that photoluminescence can still be detected hundreds of microseconds after the initial excitation. These optical datasets can now be correlated with the structural maps collected at Diamond, providing a deeper insight into how strain directly impacts the optical properties of the material. The resulting decays are used to investigate the impact that applied tensile mechanical strain has on the recombination dynamics and defect mediated processes occurring within the CsPbBr3 microcrystals.