热历史通过结构和动力学调控卤化铅钙钛矿的光电响应
Thermal history controls the optoelectronic response of lead halide perovskites through structure and dynamics
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中文总结 AI 辅助
该研究发现热历史可通过调控卤化铅钙钛矿的局域结构动态纳米畴，改变其光电响应，热历史可作为与组分并列的材料设计变量。
中文摘要 AI 辅助
卤化铅钙钛矿是用于光伏、发光及探测的极具潜力的光电材料，其光伏效率目前已接近详细平衡极限，稳定性成为主要瓶颈。迄今研究的本征不稳定性集中于固定均匀晶格内的离子运动，本文揭示了隐藏在晶格动力学中的另一本征结构不稳定性来源。通过单晶X射线与中子漫散射、机器学习辅助分子动力学、现象学八面体倾斜模型及高光谱光致发光，绘制了基于铯、甲胺、甲脒的组分，以及含Cl、Br、I及混合X位的所有可及相的图谱，发现几乎所有组分都存在平衡态局域结构涨落：尺寸为数纳米的关联八面体倾斜动态纳米畴，会局域打破晶体对称性。三种互补的调控杠杆控制这些涨落：A位阳离子决定其对称性、形状与各向异性，从甲脒基组分中稀疏、各向异性的四方相，到名义上立方的铯基组分中密集、各向异性的正交相（为研究中局域无序程度最高的体系）；卤族元素调控动态无序与相变序列；热历史是第三种杠杆：不同升降温速率会使名义上相同的组分进入不同晶相，各相具有独特的隐藏局域有序。在MAPbI₃中，仅升温速率就能在相变范围内改变光致发光量子效率。由于这些相变发生在器件工作温度范围内，从地面热循环到极端空间环境，热历史可能在整个制备与运行过程中塑造局域结构，进而调控光电响应，使其成为与组分并列的设计变量。
英文摘要
Lead halide perovskites are promising optoelectronic materials for photovoltaics, light emission and detection. Their efficiencies in PV now approach the detailed-balance limit, leaving stability as the principal barrier. The intrinsic instabilities studied to date centre on ionic motion within a fixed, homogeneous lattice. Here we identify a further source of intrinsic structural instability, hidden in the lattice dynamics. Mapping caesium, methylammonium and formamidinium-based compositions with Cl, Br, I and mixed X-sites through all accessible phases, using single crystal X-ray and neutron diffuse scattering, machine-learning-assisted molecular dynamics, a phenomenological octahedral tilt model and hyperspectral photoluminescence, we find that nearly every composition hosts equilibrium local structural fluctuations: dynamic nanodomains of correlated octahedral tilts, a few nanometres in size, that locally break the crystallographic symmetry. Three complementary levers control them. The A-site cation sets their symmetry, shape and anisotropy, from sparse, isotropic and tetragonal in formamidinium-based compositions to dense, anisotropic and orthorhombic in nominally cubic caesium-based ones, the most locally disordered we studied. The halide controls the dynamic disorder and the phase-transition sequence. Thermal history is the third: different ramp rates drive nominally identical compositions into distinct crystallographic phases, each with its own hidden local order. In MAPbI3, the heating rate alone changes the photoluminescence quantum efficiency across the phase transition. Because these transitions lie within device operating ranges, from terrestrial thermal cycling to the extremes of space, thermal history may shape the local structure, and hence the optoelectronic response, throughout fabrication and operation, establishing it as a design variable alongside composition.
发表机构
- University of Cambridge（剑桥大学）
- Imperial College London（伦敦帝国理工学院）
- Ulsan National Institute of Science and Technology (UNIST)（蔚山科学技术院）
- Linköping University（林雪平大学）
- Chalmers University of Technology（查尔姆斯理工大学）
- Helmholtz-Zentrum Berlin für Materialien und Energie（柏林亥姆霍兹材料与能源中心）
- University of Oxford（牛津大学）
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