Flexible Cu₂ZnSn(S,Se)₄ (CZTSSe) solar cells have attracted considerable attention due to their potential application in specific areas such as power sources for wearable electronics. However, the over-thick Mo(S_x,Se_1−x)₂ at the back contact is one of the factors that limit the device performance. Herein, a facile strategy to inhibit the thick Mo(S_x,Se_1−x)₂ layer by adding a proper proportion of sulfur during selenization is reported. It is found that the thickness of Mo(S_x,Se_1−x)₂ can be effectively tailored via tuning the proportion of S, enabling a substantial decrease in series resistance. The suppression mechanism is mainly ascribed to the change of orientation of Mo(S_x,Se_1−x)₂ induced by S, which limits the diffusion of Se to Mo. Accordingly, the total area efficiency of the flexible CZTSSe device improves significantly from 5.5 to 8.9% with the addition of 2% S, followed by a drop with more S. Furthermore, it is demonstrated that this strategy can also be applied to both kesterite and chalcogenide absorbers deposited on rigid Mo substrates to suppress the thick Mo(S_x,Se_1−x)₂ layer, indicating the universality of this method. Overall, this work provides a general, facile, and effective approach to modify the back contact interface without introducing extra blocking layers.

中文翻译：

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一种通用且简便的 Mo(Sx,Se1−x)2 厚度定制方法，有助于高效柔性 Cu2ZnSn(S,Se)4 太阳能电池

柔性 Cu ₂ ZnSn(S,Se) ₄ (CZTSSe) 太阳能电池因其在可穿戴电子设备电源等特定领域的潜在应用而引起了广泛关注。然而，背接触处过厚的Mo(S _x ,Se _{1− x} ) ₂是限制器件性能的因素之一。本文报道了一种通过在硒化过程中添加适当比例的硫来抑制厚 Mo(S _x ,Se _{1- x} ) ₂层的简便策略。发现Mo(S _x ,Se _{1− x} ) ₂的厚度可以通过调整 S 的比例来有效定制，从而大幅降低串联电阻。抑制机制主要归因于 S引起的 Mo(S _x ,Se _{1− x} ) ₂取向的变化，这限制了 Se 向 Mo 的扩散。因此，柔性 CZTSSe 器件的总面积效率从5.5% 至 8.9%，添加 2% S，然后下降更多 S。此外，表明该策略也可应用于沉积在刚性 Mo 基板上的锌黄铜矿和硫族化物吸收剂，以抑制厚 Mo(S _x ,Se _{1− x} ) ₂层，表明了这种方法的普遍性。总体而言，这项工作提供了一种通用、简便且有效的方法来修改背接触界面，而无需引入额外的阻挡层。