Although the substitution of Cu by Ag to suppress Cu_Zn defects offers several advantages in overcoming the large open-circuit voltage (V_oc) deficit for Cu₂ZnSn(S,Se)₄ (CZTSSe) solar cells, an excellent performance has not been achieved to date primarily due to the Fermi level pinning at the CdS/absorber interface and large recombination at the absorber/Mo interface. Herein, we developed a composition grading strategy to achieve a V-shaped Ag-graded structure with a higher Ag content on both the back and front surfaces of the (Cu,Ag)₂ZnSn(S,Se)₄ (CAZTSSe) layer. The key advantages of this Ag-graded structure are as follows: the higher content towards the CdS/absorber interface can create weak n-type donor defects and retard Fermi level pinning, whereas the lower content at the interlayer maintains the conductivity and light absorption; moreover, the other higher content towards Mo back contact can effectively suppress the recombination and improve the utilization of long-wave incident light. By appropriately adjusting the Ag gradient, we demonstrated a significant increase in V_oc, and an unexpected conversion efficiency of 11.2% was achieved. This is the highest efficiency achieved to date for Ag-substituted CZTSSe solar cells, and the result supports a new aspect that synthesis of a composition-graded CAZTSSe absorber has great potential for future research.

中文翻译：

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通过Ag级活性层对有效（Cu，Ag）₂ ZnSn（S，Se）₄太阳能电池进行界面带弯曲和缺陷消除的工程

尽管用Ag替代Cu以抑制Cu _Zn缺陷在克服Cu ₂ ZnSn（S，Se）₄（CZTSSe）太阳能电池的大开路电压（V _oc）缺陷方面提供了许多优势，但仍未获得出色的性能。迄今为止取得的成就主要归因于CdS /吸收体界面处的费米能级钉扎和吸收体/ Mo界面处的大量复合。本文中，我们开发了一种成分分级策略，以在（Cu，Ag）₂ ZnSn（S，Se）₄的背面和正面实现具有较高Ag含量的V形Ag渐变结构（CAZTSSe）层。这种Ag分级结构的主要优点如下：CdS /吸收体界面的含量较高可产生弱的n型施主缺陷，并阻止费米能级钉扎，而中间层的含量较低可保持导电性和光吸收。此外，Mo背接触的其他更高含量可以有效地抑制复合，并提高长波入射光的利用率。通过适当地调整Ag梯度，我们证明了V _oc的显着增加，并且获得了意外的11.2％的转换效率。这是迄今为止Ag取代的CZTSSe太阳能电池获得的最高效率，其结果支持了一个新的方面，即成分分级的CAZTSSe吸收剂的合成在未来的研究中具有巨大的潜力。