发表机构
Universitat Politècnica de Catalunya; Research Center in Multiscale Science and Engineering, Universitat Politècnica de Catalunya（加泰罗尼亚理工大学; 加泰罗尼亚理工大学多尺度科学与工程研究中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过第一性原理计算和器件模拟，揭示低维磷族硫卤化物表面取向对带边对齐及电荷提取的关键影响，为提升MChX太阳能电池效率提供新设计原则。
AI 中文摘要
低维磷族硫卤化物（MChX；M = Bi, Sb；Ch = S, Se；X = I, Br）是有前景的用于太阳能转换的无毒半导体，然而MChX太阳能电池的功率转换效率仍低于10%，远未达到其约30%的Shockley-Queisser极限。有效的电荷提取关键取决于吸收体与电荷选择性接触之间的带边对齐，这是一种表面性质。在此，我们结合第一性原理计算与器件级建模，研究MChX家族中的表面能量学和带对齐。对晶体取向的详尽采样，包括低对称性晶面，确定了在所有八种化合物中（011）和（010）表面是最稳定的终止面。它们的形成能仅相差约0.01-0.03 J m⁻²，但它们的带边相对于彼此刚性移动高达0.8 eV。对BiSBr的漂移-扩散模拟表明，即使在一个其他方面理想、无缺陷的吸收体中，这种晶面的共存也能将开路电压降低高达0.6 V。因此，表面取向成为电荷提取的一个隐藏设计参数。这项研究可能有助于解释MChX太阳能电池理论与实验效率之间的差距，并为基于MChX的光伏和光催化技术提供了新的设计原则。
英文摘要
Low-dimensional pnictogen chalcohalides (MChX; M = Bi, Sb; Ch = S, Se; X = I, Br) are promising non-toxic semiconductors for solar energy conversion, yet the power conversion efficiencies of MChX solar cells remain below 10%, far from their Shockley-Queisser limit of $\sim$30%. Efficient charge extraction depends critically on the band-edge alignment between the absorber and the charge-selective contacts, which is a surface property. Here, we combine first-principles calculations with device-level modelling to investigate the surface energetics and band alignments across the MChX family. An exhaustive sampling of crystal orientations, including low-symmetry facets, identifies the (011) and (010) surfaces as the most stable terminations in all eight compounds. Their formation energies differ by only $\approx 0.01$-$0.03\mathrm{J\,m^{-2}}$, yet their band edges are shifted rigidly with respect to each other by up to $0.8$eV. Drift-diffusion simulations of BiSBr show that the coexistence of such facets can reduce the open-circuit voltage by up to $0.6$V, even in an otherwise ideal, defect-free absorber. Surface orientation thus emerges as a hidden design parameter for charge extraction. This study may help to explain the gap between the theoretical and experimental efficiencies of MChX solar cells, and it provides new design principles for MChX-based photovoltaic and photocatalytic technologies.
Comments10 pages, 5 figures
