Sulfide kesterite Cu₂ZnSnS₄ (CZTS)—a non-toxic and low-cost photovoltaic material—has always faced severe charge recombination and poor carrier transport, resulting in its cell efficiency record stagnating at around 11% for years. The implementation of gradient bandgaps is a promising approach to relieving these issues, but it has not been effectively realized in kesterite solar cells due to challenges around controlling the elemental distribution. Here, based on Cd-alloyed CZTS, we propose a pre-crystallization strategy to reduce the intense vertical mass transport and Cd rapid diffusion in the film growth process, thereby realizing a Cd-gradient CZTS absorber. This absorber, exhibiting a downward-bent conduction band structure, effectively enhances the bulk carrier transport and additionally improves the interface properties of the CZTS/CdS heterojunction. These benefits significantly enhance the photoelectric conversion performance of the cell and help in achieving a certified total-area cell efficiency of about 13.2% with obviously reduced voltage loss, realizing a substantial step forward for the pure-sulfide kesterite solar cell.

硫化物钙钛矿 Cu₂ZnSnS₄ （CZTS） 是一种无毒且低成本的光伏材料，一直面临严重的电荷复合和不良的载流子传输，导致其电池效率记录多年来停滞在 11% 左右。梯度带隙的实现是缓解这些问题的一种很有前途的方法，但由于控制元素分布的挑战，它尚未在 Kesterite 太阳能电池中有效实现。在这里，基于 Cd 合金 CZTS，我们提出了一种预结晶策略，以减少薄膜生长过程中强烈的垂直质量传递和 Cd 快速扩散，从而实现 Cd 梯度 CZTS 吸收剂。这种吸收器表现出向下弯曲的导带结构，有效地增强了散货船的传输，并进一步改善了 CZTS/CdS 异质结的界面特性。这些好处显着提高了电池的光电转换性能，并有助于实现约 13.2% 的认证总面积电池效率，并明显降低了电压损失，实现了纯硫化物钙钛矿太阳能电池的实质性进步。