Positional irradiance measurement: characterization of spectrum-splitting and concentrating optics for photovoltaics

Cristofer A. Flowers; Sunita Darbe; Carissa N. Eisler; Junwen He; Harry A. Atwater

doi:10.1117/12.2062245

7 October 2014 Positional irradiance measurement: characterization of spectrum-splitting and concentrating optics for photovoltaics

Cristofer A. Flowers, Sunita Darbe, Carissa N. Eisler, Junwen He, Harry A. Atwater

Author Affiliations +

Proceedings Volume 9175, High and Low Concentrator Systems for Solar Energy Applications IX; 91750F (2014) https://doi.org/10.1117/12.2062245
Event: SPIE Solar Energy + Technology, 2014, San Diego, California, United States

Abstract

Multijunction photovoltaics enable significantly improved efficiency over their single junction analogues by mitigating unabsorbed sub-bandgap photons and voltage loss to carrier thermalization. Lateral spectrum-splitting configurations promise further increased efficiency through relaxation of the lattice- and current-matching requirements of monolithic stacks, albeit at the cost of increased optical and electrical complexity. Consequently, in order to achieve an effective spectrum-splitting photovoltaic configuration it is essential that all optical losses and photon misallocation be characterized and subsequently minimized. We have developed a characterization system that enables us to map the spatial, spectral, and angular distribution of illumination incident on the subcell reception plane or emerging from any subset of the concentrating and splitting optics. This positional irradiance measurement system (PIMS) comprises four motorized stages assembled in an X-Z-RY configuration with three linear degrees of freedom and one rotational degree of freedom, on which we mount an optical fiber connected to a set of spectrometers covering the solar spectrum from 280-1700 nm. In combination with a xenon arc lamp solar simulator with a divergence half angle of 1.3 degrees, we are able to characterize our optics across the full spectrum of our photovoltaic subcells with close agreement to outdoor conditions. We have used this tool to spectrally characterize holographic diffraction efficiency versus diffraction angle; multilayer dielectric filter transmission and reflection efficiency versus filter incidence angle; and aspheric lens chromatic aberration versus optic-to-receiver separation distance. These examples illustrate the versatility of the PIMS in characterizing optical performance relevant to both spectrum-splitting and traditional multijunction photovoltaics.

Citation Download Citation

Cristofer A. Flowers, Sunita Darbe, Carissa N. Eisler, Junwen He, and Harry A. Atwater "Positional irradiance measurement: characterization of spectrum-splitting and concentrating optics for photovoltaics", Proc. SPIE 9175, High and Low Concentrator Systems for Solar Energy Applications IX, 91750F (7 October 2014); https://doi.org/10.1117/12.2062245

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