eV), [1][2][3] remarkable absorption coefficient (≈10 5 cm −1 ), [4,5] excellent stability, and low-toxicity component. To promote the power conversion efficiency, many methods have been successfully applied to fabricate Sb 2 (S x ,Se 1-x ) 3 solar cells. For example, the rapid thermal evaporation (RTE) method [6] have been gathered many attentions for the fabrication of Sb 2 Se 3 solar cells. Recently, Tang and co-workers used a novel vapor transport deposition (VTD) way to refresh the recorded efficiency of Sb 2 Se 3 solar cell to 7.6%, [7] which has been made a great progress since Sb 2 Se 3 was successfully achieved a power conversion efficiency (PCE) of 0.03% in 2002. [8] On the other hand, Choi et al. have achieved a PCE of 7.5% [9] for Sb 2 S 3 by chemical bath deposition (CBD). Although the VTD and CBD methods have achieved impressive efficiency over 7%, a number of processing issues arise in these approaches. For example, VTD deposition processes are complex and expensive. While the nonvacuums CBD method also has weaknesses such as (i) the film prepared from CBD method is tend to be amorphous; [8,10] (ii) the Sb 2 S 3 film prepared by CBD method is antimony rich which results in a higher mean coordination number (MCN) than the stoichiometric Sb 2 S 3 . It will make it too rigid to flatten out after the annealing step; [11] (iii) the Sb 2 S 3 film prepared by CBD method inevitably includes impurities such as SbOCl, Sb 2 O 3 , and Sb 2 (SO 3 ) 3 . [12][13][14] Meanwhile, although the crystalline of the film fabricated by RTE or VTD is promising, the compactness of the absorber needs a further improvement. Thus, seeking for an effective and easy-handle nonvacuum approach to improve Sb 2 (S x ,Se 1-x ) 3 thin film solar cells is urgently needed.Since the hydrothermal method is a useful method in thin film preparation, the quality and homogeneity of the film deposited by this method is remarkable, which is expected to be able to solve the problem mentioned above and cut down the cost of fabrication. Liu et al. have taken this method to prepare the Sb 2 S 3 thin films, but there is no device reported. [15] In our previous work, double buffer layer was used to tune the band align and reduce recombination, which has achieved V oc as high as 792 mV based on hydrothermal derived Sb 2 (S x ,Se 1-x ) 3 solar cell. [16] But the thick buffer layer (60 nm TiO 2 + 60 nm CdS) inevitably increases the R s of device and decreases the transmittance as well, both of which will reduce J sc and PCE. Besides, the formation mechanism for Sb 2 S 3 thin films based Antimony sulfide-selenide Sb 2 (S,Se) 3 as a promising absorber material has drawn extensive attention owing to its rewarding photoelectric properties, low toxicity, and earth abundant components. Here, an available and highly effective method, in situ hydrothermal growth accompanied with postselenization, is successfully applied to fabricate Sb 2 (S,Se) 3 solar cells. The rationale for the preparation of Sb 2 S 3 precursors by the hydrothermal method is discussed, and ...
