Stressing Halide Perovskites with Light and Electric Fields

Building an understanding of the impacts that illumination and electric field have on the optoelectronic properties and structure of lead halide perovskites can be leveraged to generate an in-depth structure function relationship and inform further development of perovskite devices. Scanning probe microscopy in combination with various spectroscopic techniques extends the resolution of electronic and optical characterization into the nanoscale via local enhancement of the electric field around the tip. We use scanning tunneling microscopy (STM) techniques to study local surface inhomogeneity of mixed A-site cation/mixed halide perovskite thin films. Under pulsed 532 nm photoexcitation, changes in grain-to-grain absorption behaviors and reduction in electric band gap were observed with the use of single-molecule absorption scanning tunneling microscopy (SMA-STM). Synchrotron X-ray STM (SX-STM) is utilized to correlate the observed absorption signal changes to structural changes within the perovskite lattice. Lastly, pump-probe time-resolved X-ray absorption scattering measurements further indicate that under photoexcitation the perovskite lattice is distorted, in support of the electronic changes observed by our STM measurements.