| Summary: | Perovskite solar cells have become a popular alternative to traditional silicon solar cells due to their potential to provide high-efficiency, low-cost, and lightweight solar energy harvesting solutions. However, the multilayer architecture of perovskite solar cells demands careful investigation of the interaction and interfacing between the various layers, as they play a crucial role in determining the overall performance of the cell. In this context, the present work aims at analyzing the coupling between a spongy transparent electron-transporting layer (ETL) and perovskite in a formulation CsPbI<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mn>3</mn></msub></semantics></math></inline-formula>:EuI<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mn>2</mn></msub></semantics></math></inline-formula>. The ETL used in this work is a transparent mesoporous TiO<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mn>2</mn></msub></semantics></math></inline-formula> layer called “gig-lox” (grazing incidence angle geometry–local oxidation), which has been optimized to boost the interfacing with the perovskite for achieving a highly interconnected blend of materials. The gig-lox TiO<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mn>2</mn></msub></semantics></math></inline-formula> ETL shows a high surface wettability with respect to the perovskite solution, especially after pre-annealing at 500 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mo>°</mo></msup></semantics></math></inline-formula>C, and this enables the perovskite material to deeply infiltrate throughout it. The surface wettability of the gig-lox TiO<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mn>2</mn></msub></semantics></math></inline-formula> has been estimated by contact angle measurements, while the deep infiltration of the perovskite material has been demonstrated through X-ray diffraction and transmission electron microscopy analyses. Thanks to the achieved deep infiltration, the photo-generated charge injection from the perovskite into the mesoporous oxide is enhanced with respect to the use of a planar compact oxide, as shown by the photoluminescence measurements. The mainstay of the approach resides in the ETL that is deposited by a solvent-free sputtering method and is up-scalable for high industrial throughput.
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