Asymmetric Response Optoelectronic Device Based on Femtosecond-Laser-Irradiated Perovskite

We have explored an asymmetric optoelectronic response of an FAPb(I_0.8Br_0.2)₃ (FA = formamidine) perovskite device irradiated by a femtosecond (fs) laser at different laser-fluence values. Photoluminescence (PL) spectra indicated a blue shift from 772 nm (1.606 eV) to 745 nm (1.664 eV) and more than 80% quenching of the irradiated perovskite. The blue shift of the PL spectra can be attributed to compositional variation, which was confirmed through elemental analysis and X-ray diffraction. Two distinct characteristic time constants 193-46 ps and 1.9-0.61 ns were obtained by using fs transient absorption spectroscopy. The fast one represents recombination at the interface, whereas the slow one represents band-to-band recombination in the interior of the grain. Interestingly, after the perovskite was irradiated by a femtosecond laser with an appropriate laser fluence (0.135 J/cm²), an asymmetric I-V characteristic was achieved, which should result from irreversible electric domain deflection. Due to the electron-phonon scattering induced by defects, the degree of asymmetry was sensitive to the illumination power. As the photosensitive asymmetric I-V characteristics have a bearing on its photoelectric properties, the findings would be of value in photodiode, memory, and other photoelectric devices.