Luminescent Solar Concentrators Employing Phycobilisomes

Abstract

Solar concentrators can significantly reduce the use of expensive semiconductor materials in photovoltaic (PV) energy conversion. Luminescent solar concentrators (LSCs) are especially promising because they do not need to track the sun to obtain high optical concentration factors. [1][2][3][4][5][6] In this work, we demonstrate LSCs employing phycobilisomes, which are photosynthetic antenna complexes that concentrate excited states in red algae and cyanobacteria. [7,8] The phycobilisomes are cast in a solid-state matrix that preserves their internal Förster energy-transfer pathways and large wavelength shift between absorption and emission. Casting is a simple fabrication technique that also eliminates any need for expensive high-index glass or plastic. By comparing the performance of intact and partly decoupled complexes, we establish that energy transfer within intact phycobilisomes reduces LSC self-absorption losses by approximately (48 AE 5)%. These results suggest that phycobilisomes are a model for a new generation of cast LSCs with improved efficiency at high optical concentrations.LSCs are nontracking concentrators that redirect solar radiation into simple slab waveguides (see Fig. 1a). Light incident on an LSC is absorbed by dyes, re-emitted into a guided mode in the slab, and finally collected by a PV cell mounted at the edge of the slab. The maximum optical concentration of an LSC is theoretically limited by the wavelength shift between absorption and emission in the dye.[9] Larger wavelength shifts reduce the re-absorption of radiation already emitted into the LSC waveguide, [10,11] and alleviate compounding losses if either the photoluminescence efficiency of the dye, h PL , or the fraction of emitted light trapped in the waveguide, h trap , is less than unity.

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

“…The first effect results from partial overlap of the absorption and emission spectra of the luminophore. This overlap can be reduced with materials (for example, semiconductor quantum dots) 14,15 that have large Stokes shifts, or with alternative conversion processes based on near-field energy transfer 16 or phosphorescence 17 . The waveguide losses can be decreased by increasing the difference between the index of refraction of the LSC material and its surroundings, and by engineering the structures to avoid scattering.…”

Energy transfer in pendant perylene diimide copolymers

“…10,12 The strong distancedependence of FRET efficiency requires that the luminophores are in close proximity. This is a technical challenge in devices employing molecular chromophores, as they tend to aggregate and form quenching states as intermolecular spacing decreases.…”

“…4,5 Selecting a chromophore with little overlap between the absorbtion and emission band is the simplest way to limit reabsorption, 6 but these spectral properties rarely occur in conjunction with a high luminescence quantum yield necessary for overall device efficiency. 1,2,7,8 Another solution is to transfer optical excitations to a redder-emitting species which has a greatly decreased optical density across the waveg-uide modes 9,10 by Förster resonance energy transfer (FRET). 11 In this way, the likelihood of reabsorption is decreased compared to the case where only one chromophore is employed.…”

Spectral-based analysis of thin film luminescent solar concentrators

“…There is currently a renewed interest in this technology due to the availability of advanced materials (Ziessel et al, 2005;Currie et al, 2008;Mulder et al, 2009;Brühwiler et al, 2009;Earp et al, 2004) and sophisticated models to simulate the photon transport (Goldschmidt et al, 2008(Goldschmidt et al, , 2009. Major obstacles to be overcome are: limited stability of the luminescent species, high self-absorption, and poor knowledge of the parameters governing the efficiency 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 (Rowan et al, 2008).…”