Photocurrent and photoluminescence mapping of Au/FA0.9MA0.1PbI3 junctions: Probing carrier diffusion and thermo-optical degradation

We present a combined photocurrent (PC) and photoluminescence (PL) imaging study of FA0.9MA0.1PbI3 perovskite thin films patterned with Au gold pads forming planar Schottky junctions. From these measurements, we extract a room temperature carrier diffusion length between 6 and 10 μm, consistent with previous results on pure MAPbI3 compounds. This value decreases by a factor of 2–3 when the device temperature is raised to 75 °C. Interestingly, after 2 h of thermal stress at this temperature in ambient air, both the optical and electrical responses return to their initial levels upon cooling to room temperature, indicating reversible behavior and confirming the good thermal stability of this material at moderate operating conditions. In contrast, localized high-power laser illumination leads to irreversible degradation, characterized by the disappearance of both PL and PC signals. These results suggest that such materials can tolerate global short term temperature elevations without any permanent damage, such as those encountered under sunlight exposure.