A high-efficiency of 25.9% for perovskite/Si heterojunction tandem solar cells is achieved with an open-circuit voltage of 1.74 V contributed by ≈1.02 and ≈0.72 V from the top and bottom cells, respectively. The results demonstrate that the addition of methylammonium chloride (MACl) effectively mitigates the open-circuit voltage loss in the perovskite cell, where the MA cation tunes the bandgap while the Cl anion facilitates grain growth with less boundaries. Meanwhile, the excess lead iodide (PbI₂) caused by the evaporation of MACl plays a beneficial passivation role to achieve high open-circuit voltage. The performance of the tandem solar cells is a synergic consequence of all cations and anions considering the thickness, bandgap, phase stability, and defect in the perovskite absorber.

中文翻译：

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通过探索阳离子和阴离子的协同效应，最大限度地减少钙钛矿/硅串联太阳能电池的开路电压损失

钙钛矿/硅异质结串联太阳能电池的效率为 25.9%，开路电压为 1.74 V，分别来自顶部和底部电池的 ≈1.02 和 ≈0.72 V。结果表明，甲基氯化铵 (MACl) 的添加有效地减轻了钙钛矿电池中的开路电压损失，其中 MA 阳离子调节带隙，而 Cl 阴离子促进晶粒生长，边界较少。同时，MACl蒸发引起的过量碘化铅（PbI ₂）对实现高开路电压起到了有益的钝化作用。考虑到钙钛矿吸收体的厚度、带隙、相稳定性和缺陷，串联太阳能电池的性能是所有阳离子和阴离子的协同结果。