FAN Kaiwen ¹, CHU Qianqian ²

(1. Glasgow College, University of Electronic Science and Technology of China, Chengdu 611731, Sichuan, China;2. School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050, Gansu, China)

Extended abstract:[Significance] In the ever-evolving landscape of renewable energy technologies, the quest for sustainable and efficient photovoltaic solutions has been globally imperative. Tin-based perovskite solar cells (PSC) have emerged as a promising candidate, capturing the attention of researchers worldwide, due to their distinctive combination of low toxicity and remarkable optoelectronic performance. Unlike their lead-based counterparts, which raise concerns about environmental pollution and human health risks due to the toxicity of lead, tin-based PSC offers a more environmentally friendly alternative without compromising the essential photoelectric conversion capabilities. Their excellent optoelectronic performance, characterized by highlight absorption coefficients and efficient charge transport properties, positions them as a potential game-changer in the photovoltaic industry, holding the promise of making solar energy more accessible and sustainable. However, despite their significant potential, tin-based PSC still encounters several formidable challenges on the path to commercial viability. The first hurdle lies in the difficulties associated with preparing high-quality tin-based perovskite films. The fabrication process requires precise control over various parameters, including temperature, humidity and the concentration of precursor solutions. Secondly, the tin-based perovskite crystals and interfaces are plagued by numerous defects. These defects act as recombination centers for charge carriers, resulting in significant non-radiative recombination. Non-radiative recombination is a detrimental process that dissipates the energy of excited electrons and holes as heat instead of converting it into useful electrical energy. Another critical challenge is the energy level misalignment between the layers of tin-based PSC. The proper alignment of energy levels at the interfaces between different materials in the solar cell is essential for efficient charge extraction and transport. Therefore, tin-based PSC hold great promise but also face complex technical barriers. This paper was aimed to review the preparation methods of tin-based perovskite films and discuss the recent advancements of related photovoltaic devices. The influence mechanisms of composition engineering, additive regulation and interface optimization on device performances (such as photoelectric conversion efficiency and stability) are discussed in detail. Furthermore, the future development trends of tin-based PSC are predicted.[Progress] Research on tin-based perovskite solar cells (PSC) has advanced significantly through innovations in material preparation and device optimization. The crystal structure and preparation methods of tin-based perovskites were introduced. The preparation methods include solution-based methods, which are divided into one-step and two-step processing. One-step methods offer simplicity and scalability, while two-step methods provide better control over crystallization kinetics. Additionally, vapor deposition techniques have been adopted to minimize solvent-related defects and enhance film uniformity. The challenges limiting the performance of tin-based PSC were highlighted, primarily including Sn²⁺ oxidation, film defects and interfacial mismatches. To further enhance device performance, strategies such as composition engineering and additive engineering have been employed. Composition engineering involves modifying the perovskite structure by replacing cations (A-sites) or anions (X-site) to tailor electronic properties and improve stability. For example, incorporating mixing A-site cations (e.g., MA⁺, FA⁺ and Cs⁺) has been shown to reduce the concentration of defects and enhance film crystallization. Additive engineering, such as the use of SnF₂ or other salts, has also proven effective in suppressing Sn²⁺ oxidation and refining grain structure. Interface optimization has been another critical area of progress. By developing novel electron and hole transport materials, researchers have addressed interfacial energy-level mismatches, leading to improved charge extraction and device stability. These advancements collectively contribute to higher efficiencies and lay the foundation for the future commercialization of tin-based PSC.[Conclusions and prospects] The research progress of tin-based PSC was summarized. Such PSCs are promising for sustainable photovoltaics, due to their low toxicity and favorable optoelectronic properties. However, the challenges, like Sn²⁺ oxidation, film quality issues and interface mismatch, hindered their practical application. Strategies, such as composition engineering and interface optimization, demonstrated effectiveness but required further development. Future research should focus on mechanism and strategies to inhibit Sn²⁺ oxidation and improvement of film crystallization. Exploring tandem architectures and applying machine learning for material design could accelerate progress toward commercialization. Collaborative academic and industrial efforts are essential to realize the full potential of tin-based PSC in renewable energy.

Key words: solar cell; tin-based perovskite; photoelectric conversion efficiency; stability