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(a) Solar photon flux (left axis) with the photopic response function (right axis) plotted versus wavelength. (inset) Schematic of a visibly transparent power-producing window. (b) CIE 1976 uniform chromaticity diagram with the locations of the red (R), green (G), and blue (B) emitters of the National Television System Committee (NTSC) and High-Definition Television (HDTV) display standards highlighted, where these systems roughly utilize 470 nm, 555 nm, and 605 nm for R, G, and B components, respectively, to generate full color displays.
Calculated CRI (black) and weighted VT (red) as a function of the low (circles) and high (squares) idealized visible transmission wavelength cutoff shown schematically inset. The two fixed wavelengths on each side were iterated to find the largest visible range that resulted in a CRI > 95 (corresponding VT > 99.5%). The range of visible light is, therefore, defined as 435–670 nm for the efficiency calculations.
(a) Calculated thermodynamic limiting efficiencies for single-junction (single-bandgap) photovoltaics as a function of bandgap for transparent and semitransparent architectures with varied EQE contributions from the visible part of the spectrum. Note that the decrease in efficiency through the visible region for 0% VIS EQE (black line) stems from the reduced open-circuit voltage combined with the lack of additional photocurrent. (b) Maximum single-junction efficiencies as a function of the total level of visible transparency in the SQ thermodynamic (closed circles), practical (open triangles), and SQ spatially segmented visibly opaque (closed squares) junction limits. The corresponding relationship between the visible EQE contribution and weighted VT can be approximated by EQE + VT = 1 in the absence of reflection losses.
(a) Calculated thermodynamic (closed circles) and practical junction (open triangles) efficiency limits for photocurrent-matched, series-integrated, multi-junction transparent solar cells as a function of the number of junctions for a range of visible EQE contributions (as labeled with the corresponding VT). (b) Schematic of the series-integrated, multi-junction photovoltaics.
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