Light management for ever-thinner photovoltaics: A tutorial review

Ultra-thin solar cells, an order of magnitude thinner than conventional technologies, are an emerging device concept that enables low-cost, flexible, lightweight, and defect-tolerant photovoltaics. However, the advent of ultra-thin technologies is hindered by the fundamental challenge of poor light harvesting in thinnest absorber layers, which entails prohibitive photocurrent and efficiency penalties. Here, from a tutorial perspective, we review different light-management platforms that can overcome this inherent limitation, namely, antireflection coatings, rear mirrors, and light-trapping textures. We then review the state-of-the-art performances that have been achieved with these strategies and that have led to records of ∼20% efficiency in ∼200 nm absorbers. Finally, we identify persisting challenges and potential development avenues for attaining competitive performance with ever-thinner photovoltaic devices.