Sigalit Aharon1,Davide Ceratti2,Naga Jasti3,Llorenç Cremonesi4,Yishay Feldman1,Marco Potenza4,David Cahen1
Weizmann Institute of Science1,Institut Photovoltaïque d’Ile-de-France2,Bar-Ilan University3,University of Milan4
Sigalit Aharon1,Davide Ceratti2,Naga Jasti3,Llorenç Cremonesi4,Yishay Feldman1,Marco Potenza4,David Cahen1
Weizmann Institute of Science1,Institut Photovoltaïque d’Ile-de-France2,Bar-Ilan University3,University of Milan4
Adding a 2D character to halide perovskite (HaP) active layers in ambient-protected cells can improve their stability drastically, which is not obvious from the hydrophobic large cations that force the HaP into a 2D structure. We report now, using two-photon confocal microscopy to study the interior of single crystal, inherent photo-stability of pure 2D Pb iodide HaPs. Compared to 3D HaP crystals, the 2D ones have higher photo-stability and, under conditions equivalent to a few suns, they self-heal efficiently after photo-damage. Using both photoluminescence (PL) intensities (as function of time after photo-damage), and spectra, we compare the self-healing dynamics of 2D HaPs with n=1 or 3 ((C<sub>4</sub>H<sub>9</sub>NH<sub>3</sub>)<sub>2</sub>PbI<sub>4</sub>, (C<sub>4</sub>H<sub>9</sub>NH<sub>3</sub>)<sub>2</sub>(CH<sub>3</sub>NH<sub>3</sub>)<sub>2</sub>Pb<sub>3</sub>I<sub>10</sub>) and 3D MAPbI<sub>3</sub>. We find differences between the 2D HaPs in their response to photo-damage and ability to self-heal from different degrees of photo-damage. Based on our findings we suggest a possible chemical mechanism for photo-damage and self-healing of these 2D HaPs: the layered lattice arrangement limits out-diffusion of degradation products, facilitating damage reversal, leading to increased 2D HaP photo-stability, also improving self-healing uniformity. One of the implications of the layered structures’ resilience is transfer of their increased stability to devices, based on them, such as photovoltaic solar cells and light-emitting diodes.