Photonic Structuration of Perovskite Solar Cells Towards Enhanced Light Absorption
Anthony Maho a, Nathan Daem a, Michaël Lobet b c, Pierre Piron b, Alexandre Mayer c, Pierre Colson a, Jérôme Loicq b d, Catherine Henrist a, Rudi Cloots a, Jennifer Dewalque a
a CESAM-GREENMAT, University of Liège, Allée du Six-Août 13, Sart-Tilman, 4000 Liège, Belgium.
b Centre Spatial de Liège, Avenue du Pré-Aily, 4031 Angleur, Belgium.
c Solid-State Physics Laboratory, University of Namur, Rue de Bruxelles 61, 5000 Namur, Belgium.
d Delft University of Technology, PO Box 5, 2600 AA Delft, The Netherlands.
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)
València, Spain, 2022 May 19th - 25th
Organizers: Pablo Docampo, Eva Unger and Elizabeth Gibson
Contributed talk, Anthony Maho, presentation 052
Publication date: 20th April 2022

Photonic structures have attracted a lot of attention due to their ability to efficiently manage light absorption in various optoelectronic materials. Among multiple approaches, highly-ordered opal structures can be experimentally designed from the self-assembly of sacrificial monodisperse sub-micrometer spheres as colloidal photonic crystals, using wet chemistry methodologies. A corresponding strategy is considered here for the processing of 3D-structured layers in perovskite solar cells (PSCs) so to enhance light harvesting properties due to the excitation of quasi-guided modes within the photoactive layer [1,2], while facilitating the further incorporation of the materials and consequently at improving the charge extraction and separation, and impact the photoconversion efficiency.

Practically, polystyrene beads are considered as hard templating sacrificial agents for the design of inverse-opal electron-conducting TiO2 [3] or of CH3NH3PbI3 perovskite porous layers [submitted] through spin coating protocols, from which full solid-state architectures of PSCs are consecutively assembled (see TOC graphic). The positive effect of the porous structuration of the photoactive layers in comparison with dense, unstructured counterparts is demonstrated. Moreover, the specific impact of the pore dimensions on the morphological and optoelectronic properties of the structured layers is studied through structural (SEM, XRD), optical (UV-VIS-NIR, ellipsometry) and electronic analyses (I-V curves, EIS). The influence on the photon absorption intensity and lifetime on the charge recombination mechanisms within structured and unstructured active layers is further discussed.

Ultimately, optimums of structural configurations are experimentally established in terms of light harvesting and of power conversion efficiency, in good correspondence with recent numerical studies. Maximized light absorption is reached for 500 nm diameter pores structure, with photonic enhancement factors as high as 9% with inverse opal TiO2 photoanodes and 16% with inverse opal perovskite layers, compared to unstructured compact benchmarks.

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