Felix Lang

Combining high efficiency with good radiation tolerance, perovskite solar cells (PSCs) are promising candidates to upend expanding space photovoltaic (PV) technologies. Successful employment in a Near‐Earth space environment, however, requires high resistance against atomic oxygen (AtOx). This work unravels AtOx‐induced degradation mechanisms of PSCs with and without phenethylammonium iodide (PEAI) based 2D‐passivation and investigates the applicability of ultrathin silicon oxide (SiO) encapsulation as AtOx barrier. AtOx exposure for 2 h degraded the average power conversion efficiency (PCE) of devices without barrier encapsulation by 40% and 43% (w/o and with 2D‐PEAI‐passivation) of their initial PCE. In contrast, devices with a SiO‐barrier retained over 97% of initial PCE. To understand why 2D‐PEAI passivated devices degrade faster than less efficient non‐passivated devices, various opto‐electrical and structural characterications are conducted. Together, these allowed to decouple different damage mechanisms. Notably, pseudo‐ J–V curves reveal unchanged high implied fill factors (pFF) of 86.4% and 86.2% in non‐passivated and passivated devices, suggesting that degradation of the perovskite absorber itself is not dominating. Instead, inefficient charge extraction and mobile ions, due to a swiftly degrading PEAI interlayer are the primary causes of AtOx‐induced device performance degradation in passivated devices, whereas a large ionic FF loss limits non‐passivated devices.