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Material processing is critical for obtaining high-performance solar cells, which influences the morphological, crystal, and electrical properties of the functional materials in a device. Sb 2 (S,Se) 3 can be considered as a quasi-binary compound since sulfur and selenium can be alloyed with a continuous ratio due to the identical crystal structure of Sb 2 S 3 and Sb 2 Se 3 and close ionic radius between sulfur and selenium. [1-3] This simple chemical composition allows for facile synthesis of Sb 2 (S,Se) 3 film with a well-defined crystal structure. In this regard, both

Continuously boosting the power conversion efficiency (PCE) and delving deeper into its functionalities are essential problems faced by the very new antimony selenosulfide (Sb2(S,Se)3) solar technology. Here, a convenient and effective solution post‐treatment (SPT) technique is used to fabricate high‐performance Sb2(S,Se)3 solar cells, where alkali metal fluorides are applied to improve the quality of Sb2(S,Se)3 films in terms of morphology, crystallinity, and conductivity. In particular, this approach is able to manipulate the S/Se gradient in the films and creates favorable energy alignment which facilitates the carrier transport. As a result, the fill factor and short‐circuit current density of Sb2(S,Se)3 solar cells (Glass/FTO/Zn(O,S)/CdS/Sb2(S,Se)3/Spiro‐OMeTAD/Au) based on the SPT strategy are significantly enhanced, achieving a champion efficiency of 10.7%. To date, this conversion efficiency value represents the highest efficiency of all Sb‐based solar cells. This study provides an effective post‐treatment strategy for improving the quality of Sb2(S,Se)3 film which sheds new light on the fabrication of high‐efficiency Sb2(S,Se)3 solar cells.

SbS is a kind of new light-absorbing material possessing high stability in ambient environment, high absorption coefficient in the visible range, and abundant elemental storage. To improve the power conversion efficiency of SbS-based solar cells, here we control the defect in SbS absorber films. It is found that the increase of sulfur vacancy is able to upgrade photovoltaic properties. With the increase in sulfur vacancy, the carrier concentrations are increased. This n-type doping gives rise to an upshift of the Fermi level of SbS so that the charge transport from SbS to the electron selection material becomes dynamically favorable. The introduction of ZnCl in film fabrication is also found to regulate the film growth for enhanced crystallinity. Finally, the photovoltaic parameters, short-circuit current density, open-circuit voltage, and the fill factor of the device based on the SbS film are all considerably enhanced, boosting the final power conversion efficiency from 5.15 to 6.35%. This efficiency is the highest value in planar heterojunction SbS solar cells and among the top values in all kinds of SbS solar cells. This research provides a fundamental understanding regarding the properties of SbS and a convenient approach for enhancing the performance of SbS solar cells.

Antimony trisulfide (Sb2S3) is a kind of emerging light-harvesting material with excellent stability and abundant elemental storage. Due to the quasi-one-dimensional symmetry, theoretical investigations have pointed out that there exist complicated defect properties. However, there is no experimental verification on the defect property. Here, we conduct optical deep-level transient spectroscopy to investigate defect properties in Sb2S3 and show that there are maximum three kinds of deep-level defects observed, depending on the composition of Sb2S3. We also find that the Sb-interstitial (Sbi) defect does not show critical influence on the carrier lifetime, indicating the high tolerance of the one-dimensional crystal structure where the space of (Sb4S6)n ribbons is able to accommodate impurities to certain extent. This study provides basic understanding on the defect properties of quasi-one-dimensional materials and a guidance for the efficiency improvement of Sb2S3 solar cells.

According to Shockley-Queisser's theory, the maximum power conversion efficiency (PCE) of a single-junction Sb 2 S 3 solar cell is up to 28.64%. [2] Owing to the wide band gap (≈1.7 eV), it is also a suitable candidate for tandem solar cell applications. As an emerging solar cell material, its device efficiency has fallen far short of expectations and has remained limited for 8 years. [3] It has been acknowledged that the material processing method plays a vital role in improving device efficiency. In this regard, tremendous efforts have been made in developing film deposition techniques for Sb 2 S 3 absorbers, including hydrothermal, chemical bath deposition (CBD), fast chemical approach, vapor transport deposition, thermal evaporation, rapid thermal evaporation, atomic layer deposition, and closed space sublimation. [4] Among them, the CBD approach is featured as simple operation, low cost and high production capacity, [5] and the systematical survey (Figure 1f) suggested that the overall PCEs of Sb 2 S 3 solar cells are all lower than that reported in 2014 by Choi et al. using CBD method (7.5%). [3] Therefore, CBD is recognized as the most feasible and successful method for chalcogenide film deposition.Sb 2 S 3 as a light-harvesting material has attracted great attention for applications in both single-junction and tandem solar cells. Such solar cell has been faced with current challenge of low power conversion efficiency (PCE), which has stagnated for 8 years. It has been recognized that the synthesis of highquality absorber film plays a critical role in efficiency improvement. Here, using fresh precursor materials for antimony (antimony potassium tartrate) and combined sulfur (sodium thiosulfate and thioacetamide), a unique chemical bath deposition procedure is created. Due to the complexation of sodium thiosulfate and the advantageous hydrolysis cooperation between these two sulfur sources, the heterogeneous nucleation and the S 2releasing processes are boosted. As a result, there are noticeable improvements in the deposition rate, film morphology, crystallinity, and preferred orientations. Additionally, the improved film quality efficiently lowers charge trapping capacity, suppresses carrier recombination, and prolongs carrier lifetimes, leading to significantly improved photoelectric properties. Ultimately, the PCE exceeds 8% for the first time since 2014, representing the highest efficiency in all kinds of Sb 2 S 3 solar cells to date. This study is expected to shed new light on the fabrication of high-quality Sb 2 S 3 film and further efficiency improvement in Sb 2 S 3 solar cells.

Sb2S3 as a stable light harvesting material has received increasing attention for solar cell applications. To improve the device efficiency, much effort has been put into the materials synthesis, interfacial engineering, and device structure design. Here, it is demonstrated that doping of alkali metal (Li, Na, K, Rb, Cs) ions essentially affects the morphological, crystal, optical and electrical properties of Sb2S3 films. The structural and compositional analysis shows that the doping is in form of alkali metal‐sulfur chemical bond at both surface and grain boundaries of Sb2S3 films. Compared with the pristine Sb2S3, we observe that Li and Na doping are not able to improve the device efficiency, while K, Rb, and Cs notably increase energy conversion efficiency. The most effective enhancement is found in Cs‐doped Sb2S3, where the carrier concentration, crystallinity, and film formability show remarkable improvement. The device based on the Cs‐Sb2S3 film delivers a power conversion efficiency of 6.56%, which is the highest efficiency in planar heterojunction Sb2S3 solar cells, regardless of whether the films are fabricated by a solution process or thermal deposition. This research identifies that doping of heavy alkali metals is an effective approach to improve the performance of Sb2S3 solar cells.

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