Record Efficiency Photovoltaic Heterostructures

在过去的3年里，Fafard的团队取得了突破性的光电器件进步，现在具有任何类型器件的最高光电转换效率。这一进展最近在几次受邀的国际演讲和最新的科学论文中进行了介绍。在先进的III-V异质结构领域的这一最新发展允许实现大于65%的光电转换效率。目前的建议是进一步推进这些新型III-V族半导体光传感器的理解和发展。记录效率的设备是基于一种新的垂直外延异质结构架构（VEHSA）的设计。由于对通过金属有机化学气相沉积外延或化学束外延生长的薄半导体层进行精确控制，因此可以通过适合各种应用的定制输出电压获得前所未有的性能。因此，拟议的研究是在纳米级p/n结领域，并将揭示与超薄基地，包括光子回收效应工程光伏器件非常有趣的属性。异质结构的设计产生了高的外部量子效率（EQE）值的实验研究的所有结构，多达20超薄子电池（PT 20设备）的日期。对于所有结构，包括最近的PT 20，证实了大于60%的转化效率。此外，这些高效率可以保持高的电输出功率，达到大于3 W的芯片只有几毫米2的面积。用PT 20研究的单片光伏电池获得了Voc > 23 V的高光电压值。PT 20结构已经实现了其最薄的基底，其厚度仅为24 nm，但对于未来的发展，器件建模表明，对于更高数量的异质结，预计可以实现高光电压和前所未有的转换效率值，进入二维量子阱效应变得显着的范围。例如，我们推导出PT 60结构的最靠前的子电池将具有薄至8 nm的基底，预计每个单独的子电池仍然产生1.14V的光电压，并且它将开始以二维量子阱效应为特征。该提案将使这一领域取得关键进展，同时利用在研究的非常富有成效的初始阶段取得的成就。通过在VEHSA设计中增加更多的n/p结，将使热化损耗最小化以达到更高的效率，并且将进一步增加开路电压。这些器械将内置于系统中，系统将受益于独特的器械属性。VEHSA设计也将应用于其他合金，实现更长的波长。

In the past 3 years, Fafard's team made breakthrough optoelectronic device advancements, now featuring the highest optical to electrical conversion efficiency ever for any type of devices. The progress has been presented recently at several invited international presentations and late-news scientific papers. This recent development in the area of advanced III-V heterostructures allowed attaining greater than 65% optical to electrical conversion efficiencies. The current proposal is to further advance the understanding and the development with these novel III-V semiconductor phototransducers. The record-efficiency devices are based on a novel vertical epitaxial heterostructure architecture (VEHSA) design. Thanks to a precise control of thin semiconductor layers grown by Metal-Organic Chemical Vapor Deposition epitaxy or by chemical beam epitaxy, the unprecedented performance can be obtained with tailored output voltages adapted for various applications. The proposed research is therefore in the area of nanoscale p/n junctions and will reveal very interesting properties for photovoltaic devices engineered with ultra-thin bases, including photon recycling effects. The heterostructure designs yielded high external quantum efficiency (EQE) values for all the structures studied experimentally, up to 20 ultra-thin subcells (PT20 devices) to date. Conversion efficiencies greater than 60% were confirmed for all structures, including recently the PT20s. Additionally, these high efficiencies can be maintained for high electrical output powers, reaching greater than 3W for chips only a few mm2 in area. Record high-photovoltage values for monolithic photovoltaic cells with Voc > 23V have been obtained with the PT20 studied. The PT20 structure has been implemented with its narrowest ultrathin base having a remarkable thickness of only 24nm, but for future developments, the device modeling shows that the high-photovoltage and the unprecedented conversion efficiency values are expected to be achievable for a much higher number of ultrathin junctions, getting into the range where 2-dimensional quantum well effects are becoming significant. For example, we derived that the narrowest subcell of a PT60 structure would have a base as thin as 8nm, it is expected to still generate a photovoltage of 1.14V per individual subcell, and it will begin to feature 2-dimensional quantum well effects. The proposal will enable key progress in this area while leveraging the achievements accomplished in the very fruitful initial phase of the research. The thermalization losses will be minimized to reach higher efficiencies and the open circuit voltage will be further increased by adding more n/p junctions to the VEHSA design. The devices will be built into systems that will benefit from the unique device properties. Also the VEHSA design will be implemented to other alloys, enabling longer wavelengths.