Gradient bandgap engineering has been acknowledged as an effective approach for improving the efficiency of CIGS solar cells. However, an effective method for achieving gradient bandgap engineering in quaternary sputtered CIGS films has not yet been identified.This is due to the uniform and singular nature of the quaternary target composition, as well as the complex kinetic mechanisms that result in the rearrangement of film elements (particularly Ga) during the annealing process. In this study, a grain boundary migration-driven diffusion mechanism for the Ga element in CIGS thin films was established to address the presented issue. The segregation of Ga element is believed to be caused by the flow velocity field generated from the migration of grain boundaries, and the distribution of Ga element can be precisely calculated using the mass transport equation. By modulating the V-shaped bandgap, a notable enhancement in open-circuit voltage (V) was achieved, with an increase from 0.405 V to 0.515 V, leading to an effectively improvement of solar cell's efficiency. By comparing and analyzing the actual performance parameters of the solar cells and the simulated results, we conclude that the increase in V is due to the alteration in bandgap structure. This study presents a novel approach to bandgap engineering in quaternary sputtered CIGS films through the quantitative calculation of Ga element distribution.

中文翻译：

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基于四元靶磁控溅射的CIGS薄膜Ga元素扩散机理及V型带隙调控研究

梯度带隙工程已被公认为是提高CIGS太阳能电池效率的有效方法。然而，目前尚未找到一种在四元溅射 CIGS 薄膜中实现梯度带隙工程的有效方法。这是由于四元靶材成分的均匀性和奇异性，以及导致薄膜重排的复杂动力学机制。退火过程中的元素（特别是Ga）。在这项研究中，建立了 CIGS 薄膜中 Ga 元素的晶界迁移驱动扩散机制来解决所提出的问题。 Ga元素的偏析被认为是由晶界迁移产生的流速场引起的，并且利用传质方程可以精确计算Ga元素的分布。通过调制V形带隙，开路电压（V）显着提高，从0.405 V增加到0.515 V，从而有效提高了太阳能电池的效率。通过对比分析太阳能电池的实际性能参数和模拟结果，我们得出结论：V的增加是由于带隙结构的改变所致。本研究通过定量计算 Ga 元素分布，提出了一种四元溅射 CIGS 薄膜带隙工程的新方法。