Kavanagh Seán R, Savory Christopher N, Liga Shanti M, Konstantatos Gerasimos, Walsh Aron, Scanlon David O
Thomas Young Centre and Department of Chemistry, University College London, 20 Gordon Street, LondonWC1H 0AJ, U.K.
Thomas Young Centre and Department of Materials, Imperial College London, Exhibition Road, LondonSW7 2AZ, U.K.
J Phys Chem Lett. 2022 Dec 1;13(47):10965-10975. doi: 10.1021/acs.jpclett.2c02436. Epub 2022 Nov 22.
Low-cost, nontoxic, and earth-abundant photovoltaic materials are long-sought targets in the solar cell research community. Perovskite-inspired materials have emerged as promising candidates for this goal, with researchers employing materials design strategies including structural, dimensional, and compositional transformations to avoid the use of rare and toxic elemental constituents, while attempting to maintain high optoelectronic performance. These strategies have recently been invoked to propose Ti-based vacancy-ordered halide perovskites (ATiX; A = CHNH, Cs, Rb, or K; X = I, Br, or Cl) for photovoltaic operation, following the initial promise of CsSnX compounds. Theoretical investigations of these materials, however, consistently overestimate their band gaps, a fundamental property for photovoltaic applications. Here, we reveal strong excitonic effects as the origin of this discrepancy between theory and experiment, a consequence of both low structural dimensionality and band localization. These findings have vital implications for the optoelectronic application of these compounds while also highlighting the importance of frontier-orbital character for chemical substitution in materials design strategies.
低成本、无毒且储量丰富的光伏材料一直是太阳能电池研究领域长期追求的目标。受钙钛矿启发的材料已成为实现这一目标的有前途的候选材料，研究人员采用了包括结构、维度和成分转变在内的材料设计策略，以避免使用稀有和有毒的元素成分，同时试图保持高光电性能。继CsSnX化合物展现出初步前景之后，这些策略最近被用于提出基于Ti的空位有序卤化物钙钛矿（ATiX；A = CHNH、Cs、Rb或K；X = I、Br或Cl）用于光伏操作。然而，对这些材料的理论研究一直高估了它们的带隙，而带隙是光伏应用的一个基本属性。在这里，我们揭示了强激子效应是理论与实验之间这种差异的根源，这是低结构维度和能带局域化共同作用的结果。这些发现对这些化合物的光电应用具有至关重要的意义，同时也突出了前沿轨道特性在材料设计策略中化学取代方面的重要性。
