Metal halide semiconductors: materials discovery beyond ABX3 perovskites

气候变化和能源安全是人类在下个世纪面临的一些最大挑战。可再生能源和提高能源效率是关键的解决办法，将使世界能够保持和提高目前的繁荣水平。尤其是光伏电池，可以实现大规模、可持续的发电：一小时内发生在地球表面的太阳能事件足以满足整个世界目前的年度能源需求。此外，用于固态照明的发光二极管可以显著降低照明的电力需求，但仍需要进一步提高每种特定光线质量的成本。这些领域的进一步进展关键取决于新型半导体材料的发现和开发，这种材料可以有效地将光转化为电能，反之亦然。最近，杂化金属卤化物钙钛矿半导体在光伏和发光设备中的应用尤其令人兴奋。这些材料现在提供的太阳能电池的单结薄膜电池的功率转换效率超过25%(接近30%的热力学限制)，以及高效的发光二极管。然而，目前这类ABX3金属卤化物钙钛矿仍然存在一些问题，包括性能最好的材料中加入的铅的毒性，以及更高效率的串联太阳能电池和颜色可调发光所需的长期材料稳定性和稳定的带隙可调性。因此，在这一点上，发现一种能够克服这些问题的新的半导体目录将是非常令人兴奋的。这一研究计划将使人们能够在更广泛的金属卤化物组成中发现新的半导体(除了现在已经确立的ABX3钙钛矿组成之外)，这一发现仍未被探索到令人惊讶的程度。新材料的发现将通过一个紧密联系的反馈回路来实现，该回路基于四名合作研究人员的互补和世界领先的专业知识组合，包括计算建模和预测、材料合成、薄膜制造和钝化以及组合光谱表征。这些活动将按三个明确的方向发展，侧重于计算设计、材料合成和加工以及关键材料性能的实验评估。这些链将并行进行，将非常好地相互关联，并作为反馈循环的一部分进化，在反馈循环中，一条链中的任何新发现都将向其他两条链提供高度有用的信息。这种协调一致的努力将使我们能够将新半导体的发现从目前缓慢、反复试验、大海捞针的搜索，转变为对一大批潜在候选材料的快速、有针对性和系统的探索。这种定向发现将发现一个新的高性能材料库，因为目前可用的材料很可能只是实际可用的、但尚未发现的半导体的冰山一角。

Climate change and energy security are some of the greatest challenges to be faced by mankind over the coming century. Renewable sources of energy and increases in energy efficiency are key solutions that will allow the world to maintain and enhance its current level of prosperity. Photovoltaic cells, in particular, allow large-scale, sustainable generation of electricity: the solar energy incident on the surface of the earth in one hour is enough to provide the whole world's current annual energy requirements. In addition, light-emitting diodes for solid-state lighting can significantly reduce the power demand for lighting, but still require further improvements in cost per given quality of light. Further advances in these fields rely crucially on the discovery and development of new semiconducting materials that can efficiently turn light into electricity, and vice versa.The relatively recent use of hybrid metal halide perovskite semiconductors in photovoltaic and light-emitting devices has been particularly exciting here. These materials now deliver solar cells with power conversion efficiencies exceeding 25% for single-junction thin-film cells (close to the thermodynamic limit of 30%), and efficient light-emitting diodes. However, some issues remain with this current class of ABX3 metal halide perovskites, including toxicity of lead which is incorporated in the highest performing materials, as well as long-term material stability, and stable band-gap tunability, required for higher efficiency tandem solar cells and colour-tunable light emission. Therefore, the discovery of a new catalogue of semiconductors which overcome such issues would be extremely exciting at this point.This research programme will enable the discovery of new semiconductors within the broader class of metal-halide compositions (beyond the now well-established group of ABX3 perovskites) which is still unexplored to a surprising extent. New materials discovery will be enabled by a closely-knit feedback loop based on the complementary and world-leading expertise portfolios of the four co-investigators, encompassing computational modelling and prediction, materials synthesis, thin-film fabrication and passivation and combinatorial spectroscopic characterization. These activities will evolve in three well-defined strands, focusing on computational design, materials synthesis and processing, and experimental assessment of critical material properties. These strands will be carried out in parallel, will be exceptionally well interlinked, and evolve as part of a feedback loop in which any new finding in one strand will feed highly useful information into the other two strands. This co-ordinated effort will allow us to turn discovery of new semiconductors from the current slow, trial-and-error, needle-in-a-haystack search into a rapid, targeted and systematic exploration of a vast group of potential candidate materials. Such directed discovery will unearth a new library of high-performance materials, given that the currently available materials are likely to be just the tip of the iceberg of actually available, but as yet undiscovered semiconductors.