Polymeric substrates structured by roll-to-roll nano-imprint lithography for flexible perovskite solar cells with improved light management

SOLDERA, FLAVIO A.; LASAGNI, ANDRÉS FABIÁN; WANG, QIONG; ABATE, ANTONIO; SOLDERA, MARCOS M.; LANG, VALENTIN

Conferencia; 12th Conference on Hybrid and Organic Photovoltaics, HOPV20 Online Conference; 2020

nanoGe

Flexible perovskite solar cells are a promising efficient energy source in niche markets, such as in building integrated photovoltaics, portable devices and indoor electronic. Furthermore, flexible substrates allow the production of the whole solar module in roll-to-roll facilities which can significantly lower the manufacturing costs [1]. In order to further increase the device efficiency, a careful optical light management is needed to maximize the sunlight harvest without compromising the overall electrical performance. One possible path to pursue this goal is texturing the substrate before the deposition of the thin films, so that incoming light can be scattered or diffracted by the microfeatures enabling a light trapping effect inside the perovskite layer. In this contribution, an industrial scalable method is employed to structure polyethylene terephthalate (PET) foils suitable for substrates in flexible perovskite solar cells [2]. In the first step, a cylindrical Ni mold (300 mm length, 300 mm diameter) is structured with a periodic line-like texture using Direct Laser Interference Patterning (DLIP). In the second step, the microtexture in the Ni mold is transferred to PET foils by nanoimprint lithography (NIL) in a roll-to-roll process at a throughput of 1 m2/min. The topography characterization by confocal microscopy and scanning electron microscopy revealed that the texture of PET had a good overall uniformity and the grooves had a spatial period of 2.7 m and an aspect ratio of 0.22 [3]. Afterwards triple cation solar cells with a layer stack ITO/SnOx/perovskite/spiro-OMeTAD/Au were deposited onto these substrates. Current-voltage measurements showed that the textured solar cells delivered on average a 8% higher photocurrent than similar devices deposited on flat PET. UV-vis spectroscopic characterization with an integrating sphere suggests that the increase in the photocurrent is caused by a reduction of the textured solar cells? spectral reflectivity [4].[1] Krebs F C, Gevorgyan S A and Alstrup J 2009 A roll-to-roll process to flexible polymer solar cells: model studies, manufacture and operational stability studies Journal of Materials Chemistry 19 5442[2] Rank A, Lang V and Lasagni A F 2017 High-Speed Roll-to-Roll Hot Embossing of Micrometer and Sub Micrometer Structures Using Seamless Direct Laser Interference Patterning Treated Sleeves Adv. Eng. Mater. 19 1700201[3] Soldera M, Wang Q, Soldera F, Lang V, Abate A and Lasagni A F 2020 Patterning of transparent polymers using high-throughput methods: application in flexible perovskite solar cells with enhanced light trapping Laser-based Micro- and Nanoprocessing XIV Laser-based Micro- and Nanoprocessing XIV vol 11268 (International Society for Optics and Photonics) p 112680K[4] Soldera M, Wang Q, Soldera F, Lang V, Abate A and Lasagni A F 2020 Toward High-Throughput Texturing of Polymer Foils for Enhanced Light Trapping in Flexible Perovskite Solar Cells Using Roll-to-Roll Hot Embossing Advanced Engineering Materials 22 1901217