Perovskite/silicon tandem solar cells are emerging as a highefficiency and prospectively cost-effective solar technology with great promise for deployment at the utility scale. However, despite the remarkable performance progress reported lately, assuring sufficient device stabilityparticularly of the perovskite top cellremains a challenge on the path to practical impact. In this work, we analyze the outdoor performance of encapsulated bifacial perovskite/silicon tandems, by carrying out field-testing in Saudi Arabia. Over a six month experiment, we find that the open circuit voltage retains its initial value, whereas the fill factor degrades, which is found to have two causes. A first degradation mechanism is linked with ion migration in the perovskite and is largely reversible overnight, though it does induce hysteretic behavior over time. A second, irreversible, mechanism is caused by corrosion of the silver metal top contact with the formation of silver iodide. These findings provide directions for the design of new and more stable perovskite/silicon tandems

By using ultra-sensitive techniques for mapping charge-carrier dynamics on surfaces, we revealed for the first time that photo-generated carriers can diffuse orders of magnitude higher on the surfaces of CdTe single crystals than those in the crystal's bulk. Also, we found a strong correlation between carrier-transport mobility and the orientation and termination of the investigated surfaces. The exceptional surface-carrier transport can be easily suppressed by the presence of oxide layers on polar surfaces. This phenomenon is expected to be present in other semiconductors similar to CdTe.

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Single-particle spectroscopy has demonstrated great potential for analyzing the microscopic behavior of various nanoparticles (NPs). However, high-resolution optical imaging of these materials at the nanoscale is still very challenging. Here, we present an experimental setup that combines high sensitivity of time-correlated single-photon counting (TCSPC) techniques with atomic force microscopy (AFM). This system enables single-photon detection with a time resolution of 120 ps and a spatial resolution of 5 nm. We utilize the setup to investigate the photoluminescence (PL) characteristics of both zero-dimensional (0D) and three-dimensional (3D) perovskite nanocrystals and establish a correlation between the particles’ sizes, their PL blinking, and the lifetime behavior. Our system demonstrates an unprecedented level of information, opening the door to understanding the morphology–luminescence correlation of various nanosystems.

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