The surface of individual grains of metal halide perovskite films can determine the properties of heterointerfaces at the microscale and the performance of the resultant solar cells. However, the geometric characteristics of grain surfaces have rarely been investigated. Here we elaborate on the existence of grain surface concavities (GSCs) and their effects on the charge-extracting, chemical and thermomechanical properties of buried perovskite heterointerfaces. The evolution of GSCs is triggered by grain-coalescence-induced biaxial tensile strain and thermal-coarsening-induced grain-boundary grooving. As such, GSCs are tailorable by regulating the grain growth kinetics. As a proof of concept, we used tridecafluorohexane-1-sulfonic acid potassium to alleviate biaxial tensile strain and grain-boundary grooving by molecular functionalization, thus forming non-concave grain micro-surfaces. The resultant perovskite solar cells demonstrate enhanced power conversion efficiency and elevated power conversion efficiency retention under ISOS-standardized thermal cycling (300 cycles), damp heat (660 h) and maximum power point tracking (1,290 h) tests. This work sheds light on micro-surface engineering to improve the durability and performance of perovskite solar cells and optoelectronics.

金属卤化物钙钛矿薄膜单个晶粒的表面可以决定微尺度异质界面的性质以及所得太阳能电池的性能。然而，颗粒表面的几何特征很少被研究。在这里，我们详细阐述了晶粒表面凹陷（GSC）的存在及其对埋入式钙钛矿异质界面的电荷提取、化学和热机械性能的影响。 GSC 的演化是由晶粒聚结引起的双轴拉伸应变和热粗化引起的晶界开槽触发的。因此，GSC 可以通过调节晶粒生长动力学来定制。作为概念验证，我们使用十三氟己烷-1-磺酸钾通过分子功能化来减轻双轴拉伸应变和晶界凹槽，从而形成非凹晶粒微表面。由此产生的钙钛矿太阳能电池在 ISOS 标准化热循环（300 次循环）、湿热（660 小时）和最大功率点跟踪（1,290 小时）测试中表现出增强的功率转换效率和更高的功率转换效率保持力。这项工作为微表面工程提供了线索，以提高钙钛矿太阳能电池和光电器件的耐用性和性能。