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Improving the electro-optical properties of the electron transport layers (ETLs) is considered one of the most promising solutions to increase the efficiency of the perovskite solar cells (PSCs). In this study, we focused on the spin-coated tin­(IV) sulfide (SnS2) as the ETL with two different sulfur sources, thiourea (TU) and thioacetamide (TAA) (SnS2(TU) and SnS2(TAA)), and investigated the effects of surface passivation of the prepared ETL with TU and TAA (SnS2-TU and SnS2-TAA). The treatment is shown to be useful in reducing the surface roughness of the SnS2 ETL and to passivate the interfacial trap states at the ETL/perovskite interface, leading to better contact between them. Among the prepared samples, the SnS2(TU) led to a smoother ETL rather than SnS2(TAA). Finally, the best results of the produced PSCs were related to the samples with SnS2(TU) and passivated with TAA (SnS2(TU)-TAA) in which the power conversion efficiency (PCE) promoted from 11.98% in the case of SnS2(TU) ETL to 15.14% in SnS2(TU)-TAA ETL with a 37% increase in power conversion efficiency (PCE). As an important role, TAA treatment could compensate the sulfur vacancy which was proved by XPS tests. Moreover, the SnS2(TU)-TAA ETL increased the long-term stability of the device without any encapsulation under ambient conditions, retaining 86% of the initial PCE after 30 days, while the device with the SnS2(TU) ETL could maintain about 64% of the original PCE.

Perovskite solar cell (PSC) technology experiences a remarkably rapid growth toward commercialization with certified efficiency of over 25%, along with the outstanding breakthrough in the development of SnO2. Owing to the wide bandgap, high electron mobility, chemical stability, and low photocatalytic activity, SnO2 has been the rising star to serve as electron transporting layer (ETL). More importantly, the low‐temperature fabrication process (<200 °C) enables SnO2 a promising candidate for the industry, making it compatible with the plastic substrates and large‐scale production, which is crucial for the flexible and scalable devices fabrication. In this review, the processing methods (solution‐based, vacuum‐based, and vapor‐based deposition) of low‐temperature SnO2 (LT‐SnO2) and the pros and cons of them with a focus on their scalability are discussed. Additionally, the morphologies of obtained LT‐SnO2 are investigated to guide the design and performance improvement of devices. The modification strategies to reduce undesired nonradiative recombination and passivate the defects in the bulk or at the interface of LT‐SnO2, influencing the quality of perovskite films, together with the efficiency and stability of cells are summarized. This review is a comprehensive overview of the studies on low‐temperature SnO2 ETL and provides detailed instructions for scalable PSCs.

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