Record Efficiency Photovoltaic Heterostructures

在过去的3年里，法法德的团队取得了突破性的光电设备进步，现在任何类型的设备都具有有史以来最高的光电转换效率。这一进展最近在几个受邀的国际研讨会和最新的科学论文上得到了介绍。先进的III-V异质结领域的这一最新发展使光电转换效率达到65%以上。目前的建议是进一步推进对这些新型III-V半导体光换能器的认识和发展。记录效率器件基于一种新颖的垂直外延异质结构体系结构(VEHSA)设计。由于对金属-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了精确控制，因此可以通过定制的输出电压来获得前所未有的性能，以适应各种应用。因此，这项拟议的研究是在纳米级p/n结领域进行的，并将揭示用超薄基座设计的光伏设备的非常有趣的特性，包括光子循环效应。到目前为止，异质结构设计为所有实验研究的结构产生了高的外量子效率(EQE)值，多达20个超薄子单元(PT20器件)。所有结构的转换效率都超过60%，包括最近的PT20s。此外，这些高效率可以在高电子输出功率下保持，对于面积仅为几平方毫米的芯片，可达到3W以上。通过对PT20的研究，获得了VOC和GT；23V的单片光伏电池的创纪录的高光压值。PT20结构已经实现，其最窄的超薄基区仅有24 nm的显著厚度，但对于未来的发展，器件建模表明，高光电压值和前所未有的转换效率值有望在更多的超薄结上实现，进入二维量子阱效应变得显著的范围。例如，我们推导出，PT60结构中最窄的子电池的基极将薄至8 nm，预计每个子电池仍将产生1.14V的光电压，并且它将开始具有二维量子井效应。该提案将使这一领域取得重大进展，同时利用在研究的非常富有成果的初始阶段取得的成果。通过在VEHSA设计中增加更多的n/p结，热损失将被最小化以达到更高的效率，并且开路电压将进一步增加。这些设备将内置到系统中，这些系统将受益于独特的设备属性。此外，VEHSA的设计还将应用于其他合金，从而实现更长的波长。

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.