The thermodynamic limits of light concentrators

Smestad, Greg P.; Ries, Harald; Winston, R.; Yablonovitch, Eli

doi:10.1016/0165-1633(90)90047-5

Cited by 196 publications

(141 citation statements)

References 21 publications

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“…In a typical arrangement, strips of solar cells mount on the edges of an LSC structure to collect emergent radiation. Although relatively inefficient with direct normal irradiance, this process offers levels of concentration that exceed those possible based on focusing of diffuse light, even in the thermodynamic limit 12 . Also, trackers are not required, thereby reducing the complexity and cost, and creating the possibility for mechanically flexible module designs.…”

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confidence: 99%

Flexible concentrator photovoltaics based on microscale silicon solar cells embedded in luminescent waveguides

et al. 2011

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unconventional methods to exploit monocrystalline silicon and other established materials in photovoltaic (PV) systems can create new engineering opportunities, device capabilities and cost structures. Here we show a type of composite luminescent concentrator PV system that embeds large scale, interconnected arrays of microscale silicon solar cells in thin matrix layers doped with luminophores. Photons that strike cells directly generate power in the usual manner; those incident on the matrix launch wavelength-downconverted photons that reflect and waveguide into the sides and bottom surfaces of the cells to increase further their power output, by more than 300% in examples reported here. unlike conventional luminescent photovoltaics, this unusual design can be implemented in ultrathin, mechanically bendable formats. Detailed studies of design considerations and fabrication aspects for such devices, using both experimental and computational approaches, provide quantitative descriptions of the underlying materials science and optics.

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confidence: 99%

Flexible concentrator photovoltaics based on microscale silicon solar cells embedded in luminescent waveguides

et al. 2011

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“…Experimental realizations have demonstrated a twelve-fold concentration of solar flux [2] and power conversion efficiency of 7.2%, well below the theoretical predictions of a flux concentration in excess of 100 [3] and power conversion efficiency of 26.8% [4]. Reabsorption of luminescence and subsequent re-emission into non-waveguided modes has been identified as the primary performance bottleneck [5][6][7][8][9].…”

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Nanophotonic luminescent solar concentrators

Rousseau

Wood

2013

Applied Physics Letters

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We investigate the connection between photonic local density of states and luminescent solar concentrator (LSC) performance in two manufacturable nanocavity LSC structures, a bilayer slab and a slab photonic crystal. Finite-difference time-domain electromagnetic simulations show that the waveguided luminescence photon flux can be enhanced up to 30% for the photonic crystal design over a conventional LSC operating in the ray optic limit assuming the same number of excited lumophores. Further photonic engineering could realize an increase of up to one order of magnitude in the flux of waveguided luminescence.The luminescent solar concentrator (LSC) could decrease the installed cost of solar energy through building integration [1]. The LSC, a semi-transparent waveguide with embedded lumophores, concentrates sunlight by frequency downconversion; the lumophores absorb diffuse incident sunlight and luminesce at a redder, Stokesshifted wavelength. The majority of the luminescence is emitted into modes that can be guided by total internal reflection (TIR) to the waveguide edges, upon which small-area, high efficiency solar cells are normally fastened.Despite the LSC's simplicity, the concept has not been commercialized due to low performance. Experimental realizations have demonstrated a twelve-fold concentration of solar flux [2] and power conversion efficiency of 7.2%, well below the theoretical predictions of a flux concentration in excess of 100 [3] and power conversion efficiency of 26.8% [4]. Reabsorption of luminescence and subsequent re-emission into non-waveguided modes has been identified as the primary performance bottleneck [5][6][7][8][9].While prior work has demonstrated that LSCs consisting of lumophores embedded in optical nanocavities exhibit enhanced waveguiding [10] and reduced reabsorption [11], the nanocavity modifies the photonic local density of states (LDOS) and therefore the spatial and temporal luminescence distributations [12,13]. Here, we investigate the effect of the modified LDOS on LSC performance using first-principles simulations of Maxwell's equations in two realistic nanocavity LSC designs (Fig. 1, insets). After establishing a link between photonic LDOS and LSC performance, we use finite difference time domain (FDTD) simulations to show that a nanocavity LSC can increase the flux of waveguided luminescence photons by up to 30% over a conventional LSC. Finally, we assess the maximum theoretical performance gains from LDOS engineering in the LSC.First, we define a metric of LSC performance, con- * Electronic address: vwood@ethz.ch nect the performance metric to the photonic LDOS, and determine the conditions under which LSC performance comparisons can be made on the basis of the photonic LDOS. Luminescence photons are spontaneously emitted into one of many photonic modes of the LSC. These can be divided into two groups based on the wavevector in the LSC plane (k ): non-waveguided (ω ≥ c|k |) and total internally reflected (TIR, ω < c|k |) modes. In conventional LSCs, lumophore-filled w...

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“…This constrain, obviously consistent with the second law of thermodynamic considering the Sun as heating body and the receiver (Smestad et al, 1990), is the sine brightness equation for ideal geometrical flux transfer; in its general form, with the receiver immersed in a material with refractive index n, this law is like in (3) for a 3D concentrator with axial symmetry. The θ in represents the maximal incident angle for the incoming radiation respect to the normal direction at the entrance surface allowing for a maximal ray collection, while θ out is the maximal angle for the rays at the receiver.…”

Section: Optics For Concentratorsmentioning

confidence: 82%

Photovoltaic Concentrators - Fundamentals, Applications, Market & Prospective

Antonini¹

2010

Solar Collectors and Panels, Theory and Applications

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The thermodynamic limits of light concentrators

Cited by 196 publications

References 21 publications

Flexible concentrator photovoltaics based on microscale silicon solar cells embedded in luminescent waveguides

Flexible concentrator photovoltaics based on microscale silicon solar cells embedded in luminescent waveguides

Nanophotonic luminescent solar concentrators

Photovoltaic Concentrators - Fundamentals, Applications, Market & Prospective

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