functionality such as solution processing, have been the motivation driving these technologies. Additionally, compared to more conventional photovoltaics such as silicon solar cells, the device operation principles of many of these thin fi lm photovoltaic technologies are dependent on complex physical mechanisms, such as excitonic processes, photoinduced charge separation, functional material interfaces.Whereas initial research efforts were focused on understanding the underlying device physics and improvements in power conversion effi ciency, with increasing maturity of these photovoltaic technologies, growing efforts are now being invested into the understanding of underlying degradation mechanisms and the improvement of device stability. In addition to effi ciency, increased device lifetimes are fundamental requirements for transforming these technologies into an economic viability. In early studies, many stability investigations with various stress conditions were conducted in order to gain a better understanding of the degradation mechanisms. Currently, however, a consolidation towards some common stress scenarios for stability has been pursued in order to enable a better comparability between results of different research labs worldwide. A particularly well organized large scale effort was conducted within the framework of the International Summit on Organic Solar Cell Stability (ISOS), leading to the so-called ISOS-protocols. Nowadays, During the last few decades, and in some cases only the last few years, novel thin-fi lm photovoltaic (PV) technologies such as dye-sensitized solar cells (DSSC), organic solar cells (OPV), and, more recently, perovskite-based solar cells (PSC) have been growing in maturity with respect to device performance and device stability. Together with new material systems, novel device architectures have also been introduced. Both parameters will have an effect on the overall device stability. In order to improve the understanding of degradation effects and how they can be prevented, stress testing under different conditions is commonly applied. By careful combination of stress factors and thorough analysis of photovoltaic parameter decaying curves, an understanding of the underlying degradation pathways can be gained. With the help of standardized and accelerated stress tests, as described in the ISOS-protocols, statements concerning application lifetimes can fi nally be made and compared among different labs. Once a photovoltaic technology has proven long lasting durability, the ultimate barrier for entering the commercial market are the IEC tests, taking a deeper look on overall safety and reliability, not only on durability. Here, the most prominent stress tests are reviewed, discussed and extended with respect to learning the most about photovoltaic device stability.
