The progress of selenized Cu(In,Ga)Se₂ (CIGSe) solar cells is limited by low open-circuit voltage (Voc), which results from the Ga-deficient surface and undesirable bandgap profile after selenization. Controlling the Ga grading, especially on the CIGSe surface, is challenging but critical for further efficiency improvement. Here, the simple sputtering route with K incorporation is presented to engineer single- or double-graded bandgap. The K incorporation through sputtered precursors can considerably affect the Ga profile in CIGSe during selenization, essentially distinct from reported KF post-deposition treatment, in which the Ga profile keeps unchanged. Using synchrotron-based X-ray absorption spectroscopy and first-principle calculations, we verify that Ga diffusion via Cu vacancies is restrained due to the presence of K_Cu defects. Therefore, by introducing a CuGa:KF surface layer on the bi-layer precursors, the surface Ga content of CIGSe is increased effectively, achieving a notch-like Ga distribution after selenization. This unique CuGa:KF layer significantly boosts the Voc and yields over 15% efficiency, even with a low reactive Se vapor for selenization. Our approach, completely compatible with the existing fabrication process, offers a new direction for engineering band structure without sulfurization.

硒化Cu（In，Ga）Se _2的研究进展（CIGSe）太阳能电池受低开路电压（Voc）的限制，这是由于Ga缺乏的表面和硒化后不希望的带隙分布造成的。控制Ga的分级，特别是在CIGSe表面上，具有挑战性，但对于进一步提高效率至关重要。在这里，介绍了掺入K的简单溅射路线，以设计单级或双级带隙。在硒化过程中，通过溅射的前驱体掺入的K可以显着影响CIGSe中的Ga分布，这与报道的KF沉积后处理（其中Ga分布保持不变）基本不同。使用基于同步加速器的X射线吸收光谱法和第一性原理计算，我们验证了由于K _Cu的存在，Ga通过Cu空位的扩散受到了抑制缺陷。因此，通过在双层前体上引入CuGa：KF表面层，有效地增加了CIGSe的表面Ga含量，实现了硒化后的缺口状Ga分布。这种独特的CuGa：KF层可显着提高Voc并产生超过15％的效率，即使硒化反应中的Se蒸气含量较低也是如此。我们的方法与现有的制造工艺完全兼容，为无硫化的工程带结构提供了新的方向。