RESUMEN
Organic diammonium cations are a promising component of both layered (2D) and conventional (3D) hybrid halide perovskites in terms of increasing the stability of perovskite solar cells (PSCs). We investigated the crystallization ability of phase-pure 2D perovskites based on 1,4-butanediammonium iodide (BDAI2) with the layer thicknesses n = 1, 2, 3 and, for the first time, revealed the presence of a persistent barrier to obtain BDA-based layered compounds with n > 1. Secondly, we introduced BDAI2 salt into 3D lead−iodide perovskites with different cation compositions and discovered a threshold-like nonmonotonic dependence of the perovskite microstructure, optoelectronic properties, and device performance on the amount of diammonium additive. The value of the threshold amount of BDAI2 was found to be ≤1%, below which bulk passivation plays the positive effect on charge carrier lifetimes, fraction of radiative recombination, and PSCs power conversion efficiencies (PCE). In contrast, the presence of any amount of diammonium salt leads to the sufficient enhancement of the photothermal stability of perovskite materials and devices, compared to the reference samples. The performance of all the passivated devices remained within the range of 50 to 80% of the initial PCE after 400 h of continuous 1 sun irradiation with a stabilized temperature of 65 °C, while the performance of the control devices deteriorated after 170 h of the experiment.
RESUMEN
We found that laser irradiation, being widely used in perovskite photovoltaics for both laser scribing and materials characterization, inevitably causes a cascade of complex photo- and thermochemical conjugated reactions, material melting, and ablation with deep morphological and composition changes of perovskite thin films over a much larger area compared to the initial laser spot. A crucial issue in the advancing or suppression of these degradation processes is related to the origin of the surrounding atmosphere. In particular, an effective approach utilizing an inert gas flow directed onto the exposed area is suggested for the first time to eliminate the negative consequences of perovskite laser scribing. This finding is naturally related to experimental observations of spreading the volatile decomposition products, including elemental iodine, over the pristine perovskite material, regardless of its composition, followed by laser-induced formation of liquid polyiodides. Suppression of decomposition product amount by proper selection of the gas atmosphere and power regime of the laser treatment is of interest to enhance the scribing procedure.