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.

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.

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.

Perovskite solar cells (PSCs) have emerged as an attractive technology in the photovoltaic field, due to their exceptional power conversion efficiency (PCE), solution processability and low cost. Among them, the carbon-based PSC without hole transport layer has shown great potential for application by simplifying the device structure, reducing material costs and improving environmental resistance. In the past decade, although the PCE of carbon-based PSC has been rapidly increased, the defects in perovskite materials can lead to severe carrier recombination and the reduction of carrier mobility and lifetime, thus negatively affecting the performance improvement of such devices. In addition, the inherent poor stability of perovskite thin films to external environments is not conducive to the long-term, stable, and efficient operation of devices. To address these issues, various strategies, including component engineering, additive engineering, interface engineering and device packaging technology, have been adopted to optimize the device's efficiency and stability. Among them, interface engineering has shown great potential due to its direct effect on defect enriched interface areas. In this article, tetraethyl orthosilicate (TEOS) was introduced onto the surface of perovskite. The silicon oxygen oligomers formed by the reaction between TEOS and water in air effectively passivate the surface defects of perovskite and reduce the probability of carrier recombination. Meanwhile, the protective film formed by silicon oxygen oligomers effectively prevents the penetration of moisture and oxygen from air, effectively improving the PCE and operational stability of the carbon-based PSC without hole transport layer.

TEOS/isopropanol solutions with different concentrations were spin coated onto the surface of perovskite films at a speed of 5000 r·min⁻¹ for 30 s, followed by heating at 60 ℃ for 5 min to form a passivation layer. Then, a carbon-based PSC without hole transport layer was prepared. The microstructure of the sample was observed by using a scanning electron microscope (SEM). The chemical interaction was analyzed by using Fourier transform infrared spectrometer (FTIR). To obtain the crystal structure of the sample, an X-ray diffractometer (XRD) was used. By using a fluorescence spectrometer to test steady-state fluorescence spectra (PL) and transient fluorescence spectra (TRPL), the photoexcitation characteristics and carrier behavior of the sample were studied. J-V curve was measured and calculated using AM 1.5 G and a digital source instrument.

The perovskite prepared by airflow assisted extraction method exhibits a uniform and dense surface morphology. From the PL and TRPL results, the perovskite film modified with TEOS exhibits stronger fluorescence and longer carrier lifetime (enhanced from 93.51 ns to 123.38 ns), indicating suppressed carrier recombination. In FTIR spectra, the shift of the peak clearly indicates that, after TEOS interface modification, the surface modified material undergoes bonding with perovskite. The champion PCE of the TEOS modified PSC increased from 14.52% to 16.33%. From XRD pattern, the TEOS modified perovskite film aged for 35 days at humidity ≈30% and temperature ≈25 ℃ did not show the characteristic peak of PbI₂, while the unmodified sample clearly showed the PbI₂ peak, indicating the good moisture stability of the TEOS modified perovskite film. Heated at 65 ℃ for 4 h, the unmodified sample showed that the characteristic peak of PbI₂ began to appear, while the modified samples showed no such peak, indicating the good thermal stability of the TEOS modified perovskite film. Under atmospheric conditions (humidity ≈30%, temperature ≈25 ℃), the TEOS modified devices exhibit excellent stability, with their PCE to be maintained 80% of the initial value on the 100th day.

With TEOS modification, Si-O oligomers were formed on the surface of perovskite thin films due to the reaction of TEOS and water, passivating surface defects and improving the carrier transport performance at the perovskite/carbon interface. Meanwhile, Si-O oligomers located on the surface of perovskite can greatly prevent the damage of the water and oxygen and enhance the stability of perovskite thin films and PSC devices during preparation and service. The strong interaction between Si-O oligomers and perovskite enhances the integrity and resistance to decomposition of the perovskite structure. Also, the Si-O oligomer coating could avoid the volatilization of organic components. This work is expected to provide effective support and technical guarantee for the practical application and commercial promotion of carbon-based PSC.