Tandem polymer photovoltaic cells—current status, challenges and future outlook

In this article, we review general approaches, challenges and solutions, as well as latest research progress, in the field of polymer tandem solar cells. Despite many limiting factors ranging from processing issues to characterization issues, it has been shown that high efficiency and in-depth understanding of tandem cell operation can be achieved via smart device design and analysis, and interface engineering. We further discuss in detail the operation principles and design rules of polymer tandem cells, revealing a bright future to reach double-digit power conversion efficiency from polymer tandem cells.