Efficient Light Harvesting in Thick Perovskite Solar Cells Processed on Industry-Applicable Random Pyramidal Textures
Ahmed Farag, Raphael Schmager, Paul Faßl, Philipp Noack, Bianca Wattenberg, Torsten Dippell, Ulrich W. Paetzold
Abstract
Light management is key to high-performance solar cells, particularly to monolithic perovskite/Si tandem solar cells and in real field applications. Random pyramidal textures of commercial Si solar cells (height ∼2–5 μm) allow for efficient light harvesting; however, solution processing of conventional perovskite thin films (thickness ∼0.5 μm) over these large textures exhibits bad coverage, resulting in shunting paths. In response to this challenge, we present high-efficiency perovskite solar cells (PSCs) processed on replicated industry-applicable random pyramidal textures with a smaller pyramid size of ∼1–2 μm. As a first step, we develop planar PSCs with close to micrometer thick perovskite absorber layers that maintain efficient charge carrier extraction by using a Lewis base additive and exhibit a power conversion efficiency of up to 18%. Employing these thick films in textured PSCs with inverted pyramids improves the light management as compared to the planar reference, with the AM 1.5G weighted reflectance being reduced from 9.9 to 5.2%. The reduced broadband reflectance in conjunction with enhanced light trapping increases the current generation by 7.7% relative, which corresponds to 87.3% of the maximum attainable short-circuit current density. In addition, we maintain a high fill factor and open-circuit voltage comparable to that of the planar reference PSC despite the increased surface area of the texture. Thereby, our champion textured PSC exhibits a stabilized power output of 18.7% at maximum power point tracking for 5 min. Finally, the textured PSCs also exhibit improved current generation for all angles of incidence, emphasizing their advantages at realistic irradiation conditions and for bifacial applications.