We fabricate two-dimensional Ruddlesden–Popper layered perovskite films by introducing 1-naphthylmethylamine iodide into the precursor, which forms a self-assembled multiple-quantum well (MQW) structure. Enabling outstanding electroluminescence properties, light-emitting diodes (LEDs) using the MQW structure also demonstrate significant improvement in stability in comparison with the stability of devices made from formamidinium lead iodide. To understand this, we perform electroabsorption spectroscopy, wide-field photoluminescence imaging microscopy and impedance spectroscopy. Our approach enables us to determine the mobility of iodide ions in MQW perovskites to be (1.5 ± 0.8) × 10–8 cm2 V–1 s–1, ∼2 orders of magnitude lower than that in three-dimensional perovskites. We highlight that activated ion migration is a requirement for a degradation pathway in which a steady supply of ions is needed to modify the perovskite/external contact interfaces. Therefore, the improvement in stability in a MQW perovskite LED is directly attributed to the suppressed ion migration due to the inserted organic layer acting as a barrier for ionic movement.

In this comprehensive study, the influence of (i) material specific properties (e.g., molecular weight, zero shear viscosity, D-content) and (ii) process parameters (e.g., saturation temperature, -time, -pressure, and pressure drop rate) on the expansion behavior during the autoclave foaming process were investigated on linear Polylactide (PLA) grades, to identify and evaluate the foam relevant parameters. Its poor rheological behavior is often stated as a drawback of PLA, that limits its foamability. Therefore, nine PLA grades with different melt strength and zero shear viscosity were systematically chosen to identify whether these are the main factors governing the foam expansion and whether there is a critical value for these rheological parameters to be exceeded, to achieve low density foams with fine cells. With pressure drop induced batch foaming experiments, it could be shown that all of the investigated PLA grades could be foamed without the often used chemical modifications, although with different degrees of expansion. Interestingly, PLAs foaming behavior is rather complex and can be influenced by many other factors due to its special nature. A low molecular weight combined with a high ability to crystallize only lead to intermediate density reduction. In contrast, a higher molecular weight (i.e., increased zero shear viscosity) leads to significant increased expandability independent from the D-content. However, the D-content plays a crucial role in terms of foaming temperature and crystallization. Furthermore, the applied process parameters govern foam expansion, cell size and crystallization.