Outstanding Fill Factor in Inverted Organic Solar Cells with SnO₂ by Atomic Layer Deposition

Abstract

Transport layers are of outmost importance for thin‐film solar cells, determining not only their efficiency but also their stability. To bring one of these thin‐film technologies toward mass production, many factors besides efficiency and stability become important, including the ease of deposition in a scalable manner and the cost of the different material's layers. Herein, highly efficient organic solar cells (OSCs), in the inverted structure (n‐i‐p), are demonstrated by using as electron transport layer (ETL) tin oxide (SnO2) deposited by atomic layer deposition (ALD). ALD is an industrial grade technique which can be applied at the wafer level and also in a roll‐to‐roll configuration. A champion power conversion efficiency (PCE) of 17.26% and a record fill factor (FF) of 79% are shown by PM6:L8‐BO OSCs when using ALD‐SnO2 as ETL. These devices outperform solar cells with SnO2 nanoparticles casted from solution (PCE 16.03%, FF 74%) and also those utilizing the more common sol–gel ZnO (PCE 16.84%, FF 77%). The outstanding results are attributed to a reduced charge carrier recombination at the interface between the ALD‐SnO2 film and the active layer. Furthermore, a higher stability under illumination is demonstrated for the devices with ALD‐SnO2 in comparison with those utilizing ZnO.

Understanding the Surface Chemistry of SnO2 Nanoparticles for High Performance and Stable Organic Solar Cells

“…[7,8] Moreover, ZnO has been reported to trigger photodegradation of photoactive molecules at the interface, thus strongly affecting device stability. [9,10] Recently, SnO 2 has emerged as an alternative to ZnO due to its proven high electron mobility of over 400 cm 2 V s −1 and wider bandgap, making it less sensitive to UV light. [11][12][13] Its deposition from a colloidal dispersion of nanoparticles in nontoxic solvents like ethanol or water has become a standard, especially in the field of perovskite solar cells.…”

Tuning Surface Defect States in Sputtered Titanium Oxide Electron Transport Layers for Enhanced Stability of Organic Photovoltaics

“…Several routes have been shown to mitigate this effect, for example via C 60 self-assembled monolayers or via different surface treatments that passivate the surface defects leading to the hydroxyl radical-mediated degradation mechanisms. − While some of these methods have presented good stability, they appear as challenging to scale up due to a lack of compatibility with roll-to-roll-based techniques, and thus alternative solutions must be explored. Another approach to limiting the photocatalytic degradation of NFA molecules by metal oxide ETLs is replacing TiO x and ZnO ETLs with other metal oxides that do not have a strong photocatalytic activity, e.g., SnO 2 …”

Bifunctional Urea–Polyethyleneimine‐Mediated Surface Engineering in SnO2 Electron‐Transport Layer for Efficient and Stable Organic Solar Cells

“…[26,27] To address these issues, extensive studies have been undertaken to modify the SnO 2 surface. [28][29][30][31][32][33] Amine functionalization has proven to be effective for modifying the WF of SnO 2 to be aligned with the LUMO level of Y-series NFAs. [29,30,32,33] In particular, amine-rich polyethyleneimine (PEI) has exhibited WF modification abilities originating from the strong dipole moment and hydrogen-bonding abilities of amine groups.…”