Understanding the Structural Dynamics of 2D/3D Perovskite Interfaces.

The use of 2D perovskite capping layers to passivate the surface defects of 3D perovskite active layers has become ubiquitous in high performance lead halide perovskite solar cells. However, these 2D/3D interfaces can be highly dynamic, with the structure evolving to form various mixed dimensional phases when exposed to thermal stress or illumination. Changes in the photoluminescence spectrum of formamidinium lead iodide (FAPbI) films capped with alkylammonium-based 2D perovskites as they age at 100 °C or under simulated 1 sun illumination indicate that the 2D perovskite transforms to progressively larger inorganic layer thicknesses (denoted by layer number ), eventually approaching a steady-state condition where only the 3D perovskite ( = ∞) is detectable.

A General Approach to Activate Second-Scale Room Temperature Photoluminescence in Organic Small Molecules.

Organic small molecules that exhibit second-scale phosphorescence at room temperature are of interest for potential applications in sensing, anticounterfeiting, and bioimaging. However, such materials systems are uncommon-requiring millisecond to second-scale triplet lifetimes, efficient intersystem crossing, and slow rates of nonradiative recombination. Here, a simple and scalable approach is demonstrated to activate long-lived phosphorescence in a wide variety of molecules by suspending them in rigid polymer hosts and annealing them above the polymer's glass transition temperature.

Accelerated aging of all-inorganic, interface-stabilized perovskite solar cells.

To understand degradation routes and improve the stability of perovskite solar cells (PSCs), accelerated aging tests are needed. Here, we use elevated temperatures (up to 110°C) to quantify the accelerated degradation of encapsulated CsPbI PSCs under constant illumination. Incorporating a two-dimensional (2D) CsPbICl capping layer between the perovskite active layer and hole-transport layer stabilizes the interface while increasing power conversion efficiency of the all-inorganic PSCs from 14.