All existing solar cell materials including hybrid perovskites show rather small absorption coefficient (α) of ≈10⁴ cm⁻¹ in the bandgap (E_g) transition region. The weak band‐edge light absorption is an essential problem, limiting conversion efficiency particularly in a tandem solar cell. Herein, all distorted chalcogenide perovskites (BaZrS₃, SrZrS₃, BaHfS₃, and SrHfS₃) are found experimentally to exhibit extraordinary high α exceeding 10⁵ cm⁻¹ near E_g, indicating the highest band‐edge α among all known solar cell materials. The giant absorption in the E_g region, which is consistent with the first principles, arises from the intense p–d interband transition enabled by dense S 3p valence states. For solar cell application, low‐gap BaZrS₃ derivatives, Ba(Zr,Ti)S₃ and BaZr(S,Se)₃, are further synthesized. Among the possible candidates of top‐cell materials, an earth‐abundant and nontoxic Ba(Zr,Ti)S₃ alloy shows great potential, reaching a maximum potential efficiency exceeding 38% in a chalcogenide perovskite/crystalline Si tandem architecture.

中文翻译：

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畸变硫属钙钛矿中异常强的带边吸收

所有现有的包括杂化钙钛矿的太阳能电池材料在带隙（E _g）过渡区域均显示约10 ⁴  cm ^-1的较小吸收系数（α）。弱的带边光吸收是一个基本问题，特别是在串联太阳能电池中，这限制了转换效率。在本文中，实验发现所有扭曲的硫族化物钙钛矿（BaZrS ₃，SrZrS ₃，BaHfS ₃和SrHfS ₃）在E _g附近均显示出异常高的α值，超过10 ⁵  cm ^-1，这表明带边缘的α值最高在所有已知的太阳能电池材料中。E _g区的巨大吸收与第一个原理一致，这是由密集的S 3p价态引起的强烈的p-d带间跃迁引起的。对于太阳能电池应用，可以进一步合成低能隙BaZrS ₃衍生物Ba（Zr，Ti）S ₃和BaZr（S，Se）₃。在可能用作顶层电池材料的候选材料中，富含稀土且无毒的Ba（Zr，Ti）S ₃合金显示出巨大的潜力，在硫属钙钛矿/晶体硅串联结构中，其最大潜在效率超过38％。