Atomic Layer Deposition of Functional Layers in Planar Perovskite Solar Cells

Within less than a decade of development, perovskite solar cells (PSCs) have reached efficiency levels that trigger the question about commercialization of the technology. However, the steadily increasing efficiency of PSCs is still accompanied by concerns of long-term stability and open questions about upscaled manufacturing. Atomic layer deposition (ALD) is a technique that can provide unique contributions to both issues. On top of that, ALD is an enabling technology to unlock novel options regarding device architecture and processing that are not achievable by other coating techniques. As such, ALD has enjoyed some notable recent interest from the community of perovskite photovoltaics. Herein, the current state of the art in ALD-grown functional charge transport layers for PSCs is highlighted. The most urgent scientific issues that have to be tackled are emphasized and opportunities for further research are outlined.