The study of thermoelectricity in molecular junctions is of fundamental interest for the development of various technologies including cooling (refrigeration) and heat-to-electricity conversion^1,2,3,4. Recent experimental progress in probing the thermopower (Seebeck effect) of molecular junctions^5,6,7,8,9 has enabled studies of the relationship between thermoelectricity and molecular structure^10,11. However, observations of Peltier cooling in molecular junctions—a critical step for establishing molecular-based refrigeration—have remained inaccessible. Here, we report direct experimental observations of Peltier cooling in molecular junctions. By integrating conducting-probe atomic force microscopy^12,13 with custom-fabricated picowatt-resolution calorimetric microdevices, we created an experimental platform that enables the unified characterization of electrical, thermoelectric and energy dissipation characteristics of molecular junctions. Using this platform, we studied gold junctions with prototypical molecules (Au–biphenyl-4,4′-dithiol–Au, Au–terphenyl-4,4′′-dithiol–Au and Au–4,4′-bipyridine–Au) and revealed the relationship between heating or cooling and charge transmission characteristics. Our experimental conclusions are supported by self-energy-corrected density functional theory calculations. We expect these advances to stimulate studies of both thermal and thermoelectric transport in molecular junctions where the possibility of extraordinarily efficient energy conversion has been theoretically predicted^2,3,4,14.

对分子结中的热电的研究对于包括冷却（制冷）和热电转换^1,2,3,4在内的各种技术的发展都具有根本的兴趣。在探索分子结^5,6,7,8,9的热功率（塞贝克效应）方面的最新实验进展使得能够研究热电与分子结构^10,11之间的关系。但是，仍然无法获得关于在分子连接处进行珀耳帖冷却的观察（这是建立基于分子的制冷的关键步骤）。在这里，我们报告了分子结中珀耳帖冷却的直接实验观察。通过集成导电探针原子力显微镜^12,13利用定制的皮瓦分辨率量热微器件，我们创建了一个实验平台，能够统一表征分子结的电，热电和能量耗散特性。使用这个平台，我们研究了与典型分子（Au–biphenyl-4,4'-dithiol–Au，Au–terphenyl-4,4''-dithiol–Au和Au–4,4'-bipyridine–Au）的金连接。并揭示了加热或冷却与电荷传输特性之间的关系。我们的实验结论得到了自能量校正的密度泛函理论计算的支持。我们期望这些进展将刺激对分子结中的热和热电传输的研究，在理论上已经预测了非常有效的能量转换的可能性^2,3,4,14。