Diffractive Spectral-Splitting Optical Element Designed by Adjoint-Based Electromagnetic Optimization and Fabricated by Femtosecond 3D Direct Laser Writing
Diffractive Spectral-Splitting Optical Element Designed by Adjoint-Based Electromagnetic Optimization and Fabricated by Femtosecond 3D Direct Laser Writing
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DOI：
10.1021/acsphotonics.6b00066
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发表时间：
2016-05-01
期刊：
影响因子：
7
通讯作者：
Braun, Paul V.
中科院分区：
文献类型：
--
作者：
Xiao, T. Patrick;Cifci, Osman S.;Braun, Paul V.
传统单结光伏电池最大的损耗来源是它们对全光谱阳光中所含能量的低效利用。为了克服这一缺陷，我们提出了一种多结系统，该系统将太阳光谱横向分割到具有不同带隙的单结电池的平面阵列上。作为第一个演示，我们设计、制造并表征了色散衍射光学器件，该光学器件在远场空间上分离了可见光（360-760 nm）和近红外（760-1100 nm）波段的太阳光。采用逆电磁设计优化了薄型衍射相元件的表面织构。优化后的飞秒双光子吸收三维直接激光写入薄膜在380 ~ 970 nm范围内，可见光和近红外光的平均分裂比为69.5%。在没有制造误差的情况下，劈裂效率可达80.4%。光谱分裂作用在正常入射角+/- 1度范围内观察到。进一步的设计优化和制造改进可以提高在阳光直射下的分裂效率，增加对角误差的容忍度，允许更紧凑的几何形状，并最终包含更多的光伏带隙。
The greatest source of loss in conventional single-junction photovoltaic cells is their inefficient utilization of the energy contained in the full spectrum of sunlight. To overcome this deficiency, we propose a multijunction system that laterally splits the solar spectrum onto a planar array of single-junction cells with different band gaps. As a first demonstration, we designed, fabricated, and characterized dispersive diffractive optics that spatially separated the visible (360-760 nm) and near-infrared (760-1100 nm) bands of sunlight in the far field. Inverse electromagnetic design was used to optimize the surface texture of the thin diffractive phase element. An optimized thin film fabricated by femtosecond two photon absorption 3D direct laser writing shows an average splitting ratio of 69.5% between the visible and near-infrared light over the 380-970 nm range at normal incidence. The splitting efficiency is predicted to be 80.4% assuming a structure without fabrication errors. Spectral-splitting action is observed within an angular range of +/- 1 degrees from normal incidence. Further design optimization and fabrication improvements can increase the splitting efficiency under direct sunlight, increase the tolerance to angular errors, allow for a more compact geometry, and ultimately incorporate a greater number of photovoltaic band gaps.