Charge carrier and exciton dynamics in organic-inorganic perovskite compounds

2012年首次报道了由有机-无机钙钛矿化合物制成的太阳能电池。在一年内，这些太阳能电池的效率已经从最初的3%提高到今天的15%以上。这种材料的制作很简单。因此，它已成为未来最具成本效益的光伏电池之一。从基础研究人员的角度来看，问题出现了，太阳能电池中太阳能到电能的转换机制是什么？这种材料在没有照明的情况下表现出低导电性。那么，光激发的载流子是如何在介质中传输的呢？我建议应用超快光谱学来澄清这些问题。因此，钙钛矿将使用持续时间小于十亿分之一秒的激光脉冲照射。然后用第二个同样短的激光脉冲跟踪材料的反应。这些实验结果不仅与太阳能电池的应用有关。正在研究的钙钛矿是一大类材料的一部分。这些系统都有一个共同的层状原子结构。它们最突出的代表是“石墨烯”，它由单层碳原子组成。海姆（A. Geim）和诺沃谢洛夫（K. Novoselov）因在石墨烯上进行输运测量而获得2010年诺贝尔奖。哥伦比亚大学是世界上研究这些材料的领先研究机构之一。对钙钛矿层内的电流输运以及不同层之间的相互作用的研究，可能会导致凝聚态物理中新现象的发现。

The fabrication of solar cells made from organic-inorganic perovskite compunds was first reported in 2012. Within one year, the efficiency of those solar cells has been increased from originally 3% to todays more than 15%. The production of the material is simple. Thus it has become one of the most promising candidates for cost-efficient future photovoltaics.From a basic researcher's point of view, the question arises, what the mechanisms of solar-to-electric power conversion are in those solar cells. The materials exhibit a low conductivity in the absence of illumination. So, how are photoexcited carriers transported through the medium? I propose to apply ultrafast spectroscopy to clarify these points. Therefore, perovskites will be illuminated using a laser pulse with a duration of less than a billionth of a second. The reaction of the material will then be followed using a second, similarly short laser pulse.Results of these experiments are not only relevant for application in solar cells. The perovskites under study are part of a much larger group of materials. These systems have in common a layered atomic structure. Their most prominent representative is "graphene", which consists of a single layer of carbon atoms. A. Geim and K. Novoselov were awarded the Nobel prize for transport measurements on graphene in 2010. Columbia University is one of the leading research institues in the world in research on these materials. The intended investigations on both, the current transport within individual perovskite layers as well as the interaction between different layers, may give rise to the discovery of new phenomena in condensed matter physics.