Advanced Device Concepts for Next-Generation Photovoltaics

器件架构的发展是所有光伏（PV）技术性能增强的核心。对于硅光伏电池，它们始于20世纪50年代美国贝尔实验室早期p和n掺杂研究的p-n结，并已发展为带有电荷选择性“异质结”的钝化界面，夹在均匀掺杂的单晶片上。对于金属卤化物钙钛矿，早期的光伏实施例包括钙钛矿纳米晶体“增敏”介孔TiO2，并已发展为夹在平面异质结之间的固体钙钛矿吸收层，其界面钝化程度越来越好。然而，即使是由单一的太阳能吸收材料制成的完全钝化的太阳能电池也有其局限性，理论上最大的太阳能到电力的转换效率最高为30%。规避这些限制的最流行的途径是制造“多结”或串联太阳能电池，其中多个太阳能吸收材料和设备堆叠在彼此的顶部，这导致理论上两个结的效率提高到45%，三个结的效率提高到50%以上。串联电池的领跑者是将金属卤化物钙钛矿与硅结合起来，其效率已经超过31%，我们的合作伙伴之一牛津光伏公司正在加快生产第一个钙钛矿-硅串联技术。然而，串联电池并不是光伏效率的最终决定。我们的目标是开展多学科研究，通过相互关联的工作流程，探索和构思新的光伏设备概念和范例，使光伏效率的下一个重大变化成为可能。我们的愿景基于两个关键问题；我们预测光伏技术的下一个改变游戏规则的转变是什么？为了实现这种范式转变，我们现在需要发展哪些基础科学和技术进步？我们的目标是4个设备概念；*聚光光伏，在集中的太阳光下运行，与“一个太阳”运行技术相比，功率转换效率相对提高20%至30%；*量子切割，新型卤化物半导体的稀土掺杂可以导致每吸收一个高能光子产生两个低能光子，通过光子倍增提高光伏器件中的光电流产生；*热载流子收集，通过选择性地从太阳能电池中提取热电荷来克服载流子冷却损失，将理论效率限制一直提高到66%；*和一个“光子传输”电池的新想法，设计使大多数电荷通过光子传输到电荷收集界面，消除了吸收器主体的少数载流子，消除了内部重组损失，使PV电池达到理论“辐射”极限。光伏吸收材料将基于金属卤化物钙钛矿、硅和本项目设计和发现的新型低带隙硫系卤化物半导体。通过整体方法解决这些未来的先进概念，将使我们能够在2030年后成为下一代光伏技术的第一批关键科学发现和重要的重大技术进步。

Evolution in device architectures have been central to the performance enhancements in all photovoltaic (PV) technologies. For silicon PV cells, they started as p-n junctions originating from the early p and n-doping studies in Bell Labs, USA, in the 1950s and have progressed to passivated interfaces with charge selective "heterojunctions" sandwiching homogeneously doped single crystal wafers. For metal halide perovskites, the early PV embodiments comprised perovskite nanocrystals "sensitizing" mesoporous TiO2 and have progressed to solid-perovskite absorber layers sandwiched between planar heterojunctions with increasingly well passivated interfaces. However, even a perfectly-passivated solar cell fabricated from a single solar absorber material has its limitations, with theoretical maximum solar-to-electric power conversion efficiencies topping out at 30%. The most popular route to circumvent these limitations is to create "multi-junction" or tandem solar cells, where more than one solar absorber material and device are stacked on top of each other, which leads to a theorised increase in efficiency to 45% for two junctions and over 50% for three junctions. The top runner for tandem cells is combining metal-halide perovskites with silicon, which have already demonstrated over 31% efficiency, and one of our partners, Oxford PV, is ramping up production of the first perovskite-on-silicon tandem technology. However, tandem cells are not the final word in PV efficiency. Our ambition is to carry out multidisciplinary research, via inter-linked work streams, that will explore and conceive new photovoltaic device concepts and paradigms, enabling the next major step-change in photovoltaic efficiency.We base our vision on two key questions; what do we predict to be the next game-changing transformation to PV technology? and what fundamental science and technical advances do we need to develop now, in order to deliver such a paradigm shift? We target 4 device concepts; * CONCENTRATOR PV, which operate under concentrated sun light to result in a 20 to 30% relative increase in power conversion efficiency as compared to "1-sun" operation technologies; * QUANTUM CUTTING, for which rare-earth doping of novel halide semiconductors can result in the generation of two low-energy photons for every high-energy photon absorbed, boosting the photocurrent generation in a PV device through photon-multiplication; * HOT-CARRIER COLLECTION, where carrier cooling losses are overcome by selectively extracting hot charge from a solar cell, boosting the theoretical efficiency limit all the way to 66%; * and a novel idea of a "PHOTON-TRANSPORT" cell, designed so that the majority of charges are transported to charge collection interfaces via photons, with the elimination of minority carriers from the bulk of the absorber negating internal recombination losses and enabling PV cells to reach their theoretical "radiative" limit. The PV absorber materials will be based on metal-halide perovskites, silicon, and novel low-band-gap chalcogenide-halide semiconductors designed and discovered in this project. Addressing these future advanced concepts through a holistic approach will enable us to make the first key scientific discoveries and important major technical advances in what will become the next generation of PV technologies for beyond 2030.