Optoelectronic, chemical and structural characterization of 2D PEA2PbBr4 perovskite micro-crystalline films

The remarkable potential of hybrid organic inorganic perovskite semiconductors makes them promising candidates for various applications such as solar cells, LEDs and photo-detectors. However, one critical challenge hindering their widespread commercialization is their limited long-term stability and optoelectronic quality, arising from ion migration and structural defects. This work aims to investigate the chemical and structural properties of 2D PEA2PbBr4 perovskite thin films. We used four different perovskite solutions, with distinctive fabrication parameters, to vary the grain size of the films. Current voltage (I-V) characteristics (under dark and illumination) indicate that the grain size has a strong influence on the photocurrent, in fact, samples with larger grains demonstrate higher currents than the ones with smaller grains. Via photocurrent spectroscopy, we found values for the energy gap and exciton binding energy, even though we encountered some discrepancy among the samples. Regarding the chemical characterization, we employed Glow Discharge – Optical Emission Spectroscopy (GD-OES). The results of this analysis indicate that the film was chemically uniform, avoiding compositional mismatch between the surface and the bulk, leading to unwanted and detrimental effects. As the structural characterization, scanning electron microscopy (SEM) imaging was performed in order to obtain detailed information about the grain size and grain boundaries morphology. We confirmed the diversity of grain size of the four different samples, as we expected, but we could not reveal their orientations through Electron Backscattered Diffraction (EBSD). We believe that one of the reasons for this is that the film surface was not flat enough to allow for the employment of this technique. Lastly, Photo-Induced Current Transient Spectroscopy (PICTS) was adopted to try to highlight the effect of thermally activated defects in the perovskite film, but without significant results.