Patent Publication Number: US-2012031466-A1

Title: Device and method for converting incident radiation into electrical energy using an upconversion photoluminescent solar concentrator

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of the PCT International Application No. PCT/US2010/033400 filed on May 3, 2010, the entire contents of which are hereby incorporated by reference. 
     This application claims priority of U.S. Provisional Application No. 61/174,494 filed on May 1, 2009, the entire contents of which are hereby incorporated by reference. 
    
    
     FIELD 
     This description relates generally to an upconversion photoluminescent solar concentrator and a photovoltaic device connected to the upconversion photoluminescent solar concentrator. 
     BACKGROUND 
     Light concentrators can considerably reduce the cost of electricity from photovoltaic (PV) cells. Conventional light concentrating devices and techniques utilize the direct component of radiation, thus requiring inefficient methods like solar tracking. 
     Light concentrating device for concentrating solar light using a fluorescent collector is known. The fluorescent collector converts high-frequency ultraviolet (UV) light to the visible light range through red-shifting (or via Stokes shift) the light for use by photovoltaic (PV) cells. The fluorescent collector may include a transparent sheet doped with organic dyes and/or inorganic compounds. The fluorescent collector is configured so that sunlight is absorbed by the dyes or compounds and then a photon is re-radiated isotropically. The re-radiated photon is then trapped in the sheet of the fluorescent collector by internal reflection, wherein the trapped photon may be converted at the edge of the sheet by a PV cell with a band-gap just below the luminescent energy. However, in the fluorescent collector, excess photon energy is dissipated in the collector by the luminescent red-shift (or Stokes&#39; shift) rather than in the PV cell. 
     Because conventional concentrators can access only the UV spectrum, conventional concentrators use only a limited portion of the total solar spectrum. Accordingly, a large portion of the solar spectrum cannot be used by conventional concentrators for generating electricity. Further limiting the conventional concentrators is the fact that the atmosphere filters out a significant portion of UV light from the sun. 
     BRIEF SUMMARY 
     An embodiment of an upconversion photoluminescent solar concentrator device includes a waveguide, which has a waveguide medium. The embodiment also includes an upconversion chromophore in contact with the waveguide medium. The upconversion chromophore is configured to absorb an incident photon. The upconversion chromophore is also configured to emit an emitted photon. The emitted photon has higher energy than the incident photon. 
     In another embodiment of the upconversion photoluminescent solar concentrator device, the upconversion chromophore is configured to absorb a second incident photon after the absorption of the incident photon and then emit the emitted photon, wherein the emitted photon has higher energy than the second incident photon. 
     In another embodiment of the upconversion photoluminescent solar concentrator device, the upconversion chromophore is configured to absorb the incident photon having a wavelength in infrared range, and then emit the emitted photon having a wavelength in visible, and/or near-infrared range. 
     In another embodiment of the upconversion photoluminescent solar concentrator device, the upconversion chromophore is embedded in the waveguide medium. In another embodiment of the upconversion photoluminescent solar concentrator device, the upconversion chromophore is provided at a surface of the waveguide medium. In another embodiment of the upconversion photoluminescent solar concentrator device, the upconversion chromophore is provided as a layer, a film, or a sheet, on a surface of the waveguide and/or a surface of the waveguide medium. In another embodiment of the upconversion photoluminescent solar concentrator device, the waveguide medium is a liquid, and the upconversion chromophore is suspended in the liquid. 
     In an embodiment of the upconversion photoluminescent solar concentrator device, the waveguide has a rod-like shape axially and a geometric cross-section. 
     In an embodiment of the upconversion photoluminescent solar concentrator device, the waveguide medium is transparent at a wavelength of the emitted photon. The waveguide medium is one selected from the group consisting of an amorphous silicon dioxide, a silicon dioxide, a clear plastic, a glass, an organic glass, a glass doped with a Group II-VI semiconductor and acrylic plastic. 
     In an embodiment of the upconversion photoluminescent solar concentrator device, the upconversion chromophore is an H-aggregate. An H-aggregate is used herein to describe a dye that shows a shift towards the blue or shows a hypsochromic shift. In an embodiment of the upconversion photoluminescent solar concentrator device, the upconversion chromophore is a rare-earth ion. Rare-earth ion is used herein to include a rare-earth ion nanocrystal. In an embodiment of the upconversion photoluminescent solar concentrator device, the upconversion chromophore is a rare-earth ion nanocrystal. Examples of the rare-earth ion nanocrystal are, but not limited to, neodymium (Nd 3+ ), ytterbium (Yb 3+ ), erbium (Er 3+ ), thulium (Tm 3+ ), holmium (Ho 3+ ), praseodymium (Pr 3+ ), cerium (Ce 3+ ), yttrium (Y 3+ ), samarium (Sm 3+ ), europium (Eu 3+ ), gadolinium (Gd 3+ ), terbium (Tb 3+ ), dysprosium (Dy 3+ ), and lutetium (Lu 3+ ). In an embodiment of the upconversion photoluminescent solar concentrator device, the upconversion chromophore is a lanthanide chelate. In an embodiment of the upconversion photoluminescent solar concentrator device, the upconversion chromophore is a NaYF 4  nanocrystal. 
     In another embodiment, the upconversion photoluminescent solar concentrator device further includes an antireflection coating provided on a side of the waveguide, and a taper provided on the antireflection coating, wherein a refractive index of the taper is higher than a refractive index of the waveguide medium. 
     In an embodiment of the upconversion photoluminescent solar concentrator device, the taper has a receiving surface towards the waveguide for receiving the emitted photon, and an output surface for outputting the emitted photon, wherein the output surface is smaller than the receiving surface. 
     In an embodiment of the upconversion photoluminescent solar concentrator device, the taper is a nanocrystalline diamond. In an embodiment of the upconversion photoluminescent solar concentrator device, the taper has a refractive index in a range of 2.0 to 2.6 inclusive. 
     In an embodiment of the upconversion photoluminescent solar concentrator device, a reflective surface is provided on a second side of the waveguide for reflecting the emitted photon towards the taper. In an embodiment of the upconversion photoluminescent solar concentrator device, a reflective surface is provided on multiple sides of the waveguide for reflecting the emitted photon towards the taper. 
     In an embodiment, the upconversion photoluminescent solar concentrator device also includes a photovoltaic device directly connected to the taper, wherein a refractive index of the photovoltaic device is higher than the refractive index of the taper. In an embodiment of the upconversion photoluminescent solar concentrator device, the photovoltaic device is a quantum dot, quantum well photovoltaic device, an AlGaAs/GaAs quantum well photovoltaic device, a direct band gap photovoltaic device, a silicon-based photovoltaic device, or a Group III-V direct band gap photovoltaic device. In an embodiment, the upconversion chromophore has an absorption spectrum and an emission spectrum that do not overlap. In an embodiment, the upconversion chromophore has an absorption spectrum and an emission spectrum that overlap. 
     In an embodiment, the upconversion photoluminescent solar concentrator device also includes a second upconversion chromophore, wherein the second upconversion chromophore absorbs a second incident photon and emits a second emitted photon. The second emitted photon has higher energy than the second incident photon, and the second incident photon has higher energy than the incident photon. 
     In an embodiment of the upconversion photoluminescent solar concentrator device, the upconversion chromophore has a first absorption spectrum and a first emission spectrum, wherein the first absorption spectrum and the first emission spectrum do not substantially overlap. The second upconversion chromophore has a second absorption spectrum and a second emission spectrum, and wherein the second absorption spectrum and the second emission spectrum do not substantially overlap. 
     In an embodiment of the upconversion photoluminescent solar concentrator device, the first absorption spectrum and the second absorption spectrum do not substantially overlap. In an embodiment, the first emission spectrum and the second emission spectrum overlap. In another embodiment of the upconversion photoluminescent solar concentrator device, the first emission spectrum and the second emission spectrum substantially overlap. 
     In an embodiment, the upconversion photoluminescent solar concentrator device includes a first waveguide and a second waveguide provided under the first waveguide. The first waveguide includes a first waveguide medium, and a first upconversion chromophore in contact with the first waveguide medium, wherein the first upconversion chromophore has a first absorption spectrum and a first emission spectrum, and wherein the first absorption spectrum and the first emission spectrum do not overlap. The second waveguide includes a second waveguide medium, and a second upconversion chromophore in contact with the second waveguide medium, wherein the second upconversion chromophore has a second absorption spectrum and a second emission spectrum, wherein the second absorption spectrum and the second emission spectrum do not overlap, and wherein the first absorption spectrum and the second absorption spectrum do not substantially overlap. In an embodiment, a taper provided between the first waveguide and the second waveguide, wherein a refractive index of the taper is higher than a refractive index of the first waveguide. 
     In another embodiment, the upconversion photoluminescent solar concentrator device also includes a photovoltaic device connected to the first waveguide and the second waveguide, wherein the first emission spectrum and the second emission spectrum overlap with each other, and wherein the first emission spectrum and the second emission spectrum overlap with an absorption wavelength of the photovoltaic device for converting radiation to electrical energy. 
     In an embodiment, the upconversion photoluminescent solar concentrator device includes a first taper connected to the first waveguide, wherein a refractive index of the first taper is higher than a refractive index of the first waveguide, a second taper connected to the second waveguide, wherein a refractive index of the second taper is higher than a refractive index of the second waveguide. 
     In an embodiment, the upconversion photoluminescent solar concentrator device includes a first photovoltaic device connected to the first taper, a second photovoltaic device connected to the second taper. The first emission spectrum overlaps with a first absorption wavelength of the first photovoltaic device for converting radiation to electrical energy. The second emission spectrum overlaps with a second absorption wavelength of the second photovoltaic device for converting radiation to electrical energy. 
     In an embodiment, the upconversion photoluminescent solar concentrator device includes a third photovoltaic device connected to the third taper. The third emission spectrum overlapping with a third absorption wavelength of the third photovoltaic device for converting radiation to electrical energy. 
     In another embodiment of the upconversion photoluminescent solar concentrator device, the first emission spectrum overlaps with an absorption wavelength of the photovoltaic device for converting radiation to electrical energy. 
     In another embodiment of the upconversion photoluminescent solar concentrator device, the second emission spectrum overlaps with an absorption wavelength of the photovoltaic device for converting radiation to electrical energy. 
     In another embodiment, the upconversion photoluminescent solar concentrator device also includes a third waveguide provided under the second waveguide. The third waveguide includes a third waveguide medium, and a third upconversion chromophore in contact with the third waveguide medium, wherein the third upconversion chromophore has a third absorption spectrum and a third emission spectrum, wherein the third absorption spectrum and the third emission spectrum do not substantially overlap, wherein the third absorption spectrum and the first absorption spectrum do not substantially overlap, and wherein the third absorption spectrum and the second absorption spectrum do not substantially overlap. A first taper is connected to the first waveguide, wherein a refractive index of the first taper is higher than a refractive index of the first waveguide. A second taper is connected to the second waveguide, wherein a refractive index of the second taper is higher than a refractive index of the second waveguide. A third taper is connected to the third waveguide, wherein a refractive index of the third taper is higher than a refractive index of the third waveguide. 
     In another embodiment, the upconversion photoluminescent solar concentrator device also includes a first photovoltaic device connected to the first taper, a second photovoltaic device connected to the second taper, and a third photovoltaic device connected to the third taper, wherein a refractive index of the first photovoltaic device is higher than the refractive index of the first taper, wherein the refractive index of the second photovoltaic device is higher than the refractive index of the second taper, and wherein the refractive index of the third photovoltaic device is higher than the refractive index of the third taper. 
     In another embodiment of the upconversion photoluminescent solar concentrator device, the first emission spectrum overlaps with an absorption wavelength of the photovoltaic device for converting radiation to electrical energy, the second emission spectrum overlaps with the absorption wavelength of the photovoltaic device for converting radiation to electrical energy, and the third emission spectrum overlaps with the absorption wavelength of the photovoltaic device for converting radiation to electrical energy. 
     In another embodiment of the upconversion photoluminescent solar concentrator device, the first waveguide, the second waveguide, and the third waveguide each have a rod-like shape axially and a geometric cross-section. 
     In another embodiment, the upconversion photoluminescent solar concentrator device includes a plurality of waveguides stacked together, wherein each of the plurality of waveguides has a rod-like shape axially and a geometric cross-section. Each of the plurality of waveguides includes a waveguide medium, and an upconversion chromophore in contact with the waveguide medium, wherein the upconversion chromophore is configured to absorb an incident photon and then emit an emitted photon, and the emitted photon has higher energy than the incident photon. The embodiment includes an antireflective coating provided between the plurality of waveguides and a photovoltaic device. The photovoltaic device is provided at an end side of the plurality of waveguides for receiving the emitted photon, wherein an emission spectrum of the upconversion chromophore overlaps with an absorption wavelength of the photovoltaic device for converting radiation to electrical energy. 
     In another embodiment, the upconversion photoluminescent solar concentrator device includes a second photovoltaic device provided at a second end side of the plurality of waveguides, wherein the emission spectrum of the upconversion chromophore overlaps with an absorption wavelength of the second photovoltaic device for converting radiation to electrical energy. 
     In another embodiment, a method for converting incident radiation into electrical energy is provided. The embodiment includes absorbing the incident radiation with an upconversion chromophore, emitting an emitted photon from the upconversion chromophore, wherein the emitted photon has higher energy than the incident radiation, directing the emitted photon from the upconversion chromophore to a photovoltaic device using a waveguide, and the photovoltaic device absorbing the emitted photon and converting to electrical energy. 
     In another embodiment, the method also includes absorbing a second incident radiation with a second upconversion chromophore, wherein the second incident radiation has higher energy than the incident radiation, emitting a second emitted photon from the second upconversion chromophore, wherein the second emitted photon has higher energy than the second incident radiation, directing the second emitted photon from the second upconversion chromophore to the photovoltaic device using a second waveguide, and the photovoltaic device absorbing the second emitted photon and converting to electrical energy. 
     In another embodiment, the method also includes absorbing a third incident radiation with a third upconversion chromophore, wherein the third incident radiation has higher energy than the incident radiation, emitting a third emitted photon from the third upconversion chromophore, wherein the third emitted photon has higher energy than the third incident radiation, directing the third emitted photon from the third upconversion chromophore to a third photovoltaic device using a third waveguide, and the third photovoltaic device absorbing the third emitted photon and converting to electrical energy. 
     In another embodiment, the emitted photon and the second emitted photon have the same energy. In another embodiment, the second emitted photon has higher energy than the emitted photon. 
     In an embodiment, the upconversion photoluminescent solar concentrator device includes a first waveguide including a first waveguide medium, a chromophore layer provided on a surface of the first waveguide, the chromophore layer including a plurality of upconversion chromophores in contact with the first waveguide medium. A second waveguide is provided above the chromophore layer, wherein the second waveguide includes a second waveguide medium, the plurality of upconversion chromophores in contact with the second waveguide medium. A photovoltaic device provided at an end side of the first waveguide and the second waveguide. The first waveguide is configured to direct an emitted photon from one of the plurality of the upconversion chromophores entering the first waveguide towards a photovoltaic device. The second waveguide is configured to direct the emitted photon from one of the plurality of the upconversion chromophores entering the second waveguide towards the photovoltaic device. In an embodiment, the first and/or the second waveguide medium is a liquid. In an embodiment, the first and/or the second waveguide has a rod-like shape axially and a geometric cross-section. In an embodiment, the first and/or the second waveguide medium is one selected from the group consisting of an amorphous silicon dioxide, a silicon dioxide, a clear plastic, a clear liquid, a glass, an organic glass, a glass doped with a Group II-VI semiconductor and acrylic plastic. In an embodiment, the upconversion chromophore is an H-aggregate. In an embodiment, the upconversion chromophore is a rare-earth ion. In an embodiment, an antireflection coating is provided on a side of the first and/or the second waveguide. The antireflection coating may be provided between the waveguide and the chromophore layer. A taper may be provided on a side of the waveguide with the antireflection coating being provided therebetween. In an embodiment, a refractive index of the taper is higher than a refractive index of the first and/or the second waveguide medium. The taper may have a receiving surface towards the first and/or the second waveguide for receiving the emitted photon, and an output surface for outputting the emitted photon, wherein the output surface is smaller than the receiving surface. The taper may be a nanocrystalline diamond. The taper may have a refractive index in a range of 2.0 to 2.6 inclusive. In an embodiment, the photovoltaic device is directly connected to the taper, wherein a refractive index of the photovoltaic device is higher than the refractive index of the taper. 
     In an embodiment, the absorption spectrum and the emission spectrum of one or more of the plurality of upconversion chromophores overlap. In an embodiment, the absorption spectrum and the emission spectrum of one of the plurality of upconversion chromophores substantially overlap. In an embodiment, the absorption spectrum and the emission spectrum of one or more of the plurality of upconversion chromophores completely overlap. The emitted photon can be trapped in the waveguide that the emitted photon enters such that the probability of reabsorption of the emitted photon by the upconversion chromophore is statistically low, and/or statistically non-existent. Trapping the emitted photon in the waveguide is achieved by a configuration of the waveguide that directs the emitted photon in the waveguide towards the photovoltaic device. 
     In an embodiment, an upconversion photoluminescent solar concentrator device is an encapsulated solar energy conversion device. The encapsulation includes a first protective sheet and a second protective sheet encapsulating the upconversion photoluminescent solar concentrator device therebetween. In an embodiment, a protective sheet is disposed on a top layer of an upconversion photoluminescent solar concentrator device. In an embodiment, a protective sheet is disposed on a bottom layer of an upconversion photoluminescent solar concentrator device. In an embodiment, a first protective sheet is disposed on a top layer and a second protective sheet is disposed on a bottom layer of an upconversion photoluminescent solar concentrator device, such that the first and second protective sheets sandwich the upconversion photoluminescent solar concentrator device. In an embodiment, any one or more of the protective sheets described herein is made of glass, ethylene vinyl acetate (EVA), and/or other transparent material. In an embodiment, any one or more of the protective sheets described herein includes plurality of upconversion chromophores in the material making up the protective sheet. In an embodiment, the protective sheet made of glass, EVA, and/or other transparent material has a geometric concentrating factor of 1. In an embodiment, only the top protective sheet includes upconversion chromophores. In an embodiment, the bottom protective sheet does not include upconversion chromophores. In an embodiment, both the top and bottom protective sheets include upconversion chromophores. In an embodiment, only the bottom protective sheet includes upconversion chromophores. In an embodiment, the top protective sheet does not include upconversion chromophores. In an embodiment, both the top and bottom protective sheets do not include upconversion chromophores. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device. 
         FIG. 2  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device. 
         FIG. 3  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device. 
         FIG. 4  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device. 
         FIG. 5  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device. 
         FIG. 6  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device. 
         FIG. 7  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device. 
         FIG. 8  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device. 
         FIG. 9  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device. 
         FIG. 10  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device. 
         FIG. 11  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device. 
         FIG. 12  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device. 
         FIG. 13  shows a perspective view of an embodiment of a waveguide for an upconversion photoluminescent solar concentrator device. 
         FIG. 14  shows a perspective view of an embodiment of a waveguide for an upconversion photoluminescent solar concentrator device. 
         FIG. 15(   a )-( h ) show cross-sectional views of embodiments of waveguides for an upconversion photoluminescent solar concentrator device. 
         FIG. 16  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device and absorption and emission spectrums thereof. 
         FIG. 17  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device and absorption and emission spectrums thereof. 
         FIG. 18  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device. 
     
    
    
     DETAILED DESCRIPTION 
     A method for converting incident radiation into electrical energy includes absorbing the incident radiation with an upconversion chromophore, emitting an emitted photon from the upconversion chromophore, wherein the emitted photon has higher energy than the incident radiation, directing the emitted photon from the upconversion chromophore to a photovoltaic device using a waveguide, and the photovoltaic device absorbing the emitted photon and converting to electrical energy. The method may also include absorbing a second incident radiation with a second upconversion chromophore, wherein the second incident radiation has higher energy than the incident radiation, emitting a second emitted photon from the second upconversion chromophore, wherein the second emitted photon has higher energy than the second incident radiation, directing the second emitted photon from the second upconversion chromophore to the photovoltaic device using a second waveguide, and the photovoltaic device absorbing the second emitted photon and converting to electrical energy. The method may also include absorbing a third incident radiation with a third upconversion chromophore, wherein the third incident radiation has higher energy than the incident radiation, emitting a third emitted photon from the third upconversion chromophore, wherein the third emitted photon has higher energy than the third incident radiation, directing the third emitted photon from the third upconversion chromophore to a third photovoltaic device using a third waveguide, and the third photovoltaic device absorbing the third emitted photon and converting to electrical energy. These embodiments may be carried out by using the embodiment of upconversion photoluminescent solar concentrator devices shown in the Figures and described herein. 
       FIG. 1  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device  10  that includes a waveguide  100 . The waveguide  100  includes a waveguide medium  102 . An upconversion photoluminescent chromophore  104  is in contact with the waveguide medium  102 . The upconversion chromophore  104  is configured to absorb an incident photon  106 . The upconversion chromophore  104  is configured to emit an emitted photon  108 .  FIG. 1  shows the emitted photon  108  being directed towards a photovoltaic device  110  by the waveguide  100  for converting the emitted photon  108  to electrical energy. A taper may be provided at the interface between the waveguide medium  102  and the photovoltaic device  110 . A reflective surface  112  may be provided on a side of the waveguide for reflecting the emitted photon. 
     In an embodiment, the waveguide medium  102  is transparent at a wavelength of the emitted photon  108 . The waveguide medium  102  may be glass and/or silicon oxide. Glass and silicon oxide are transparent at the photoluminescent wavelengths that travel through the waveguide medium  102 . The waveguide medium  102  may be a product from a sol-gel process. The sol-gel process evolves the sol to a gel-like network producing a sol-gel medium that contains both a liquid phase and a solid phase. The solid phase may form a colloid. The morphology of the solid phase can range anywhere from discrete colloidal particles to continuous chain-like polymer networks. One example of sol-gel medium is amorphous silicon dioxide. The sol-gel medium advantageously has a refractive index which may be adjusted to match upconversion chromophore  104 . Examples of materials for the waveguide medium  102  are, but not limited to, an amorphous silicon dioxide, a clear plastic, a clear liquid, silicon dioxide, a glass, an organic glass, a glass doped with a Group II-VI semiconductor, or acrylic plastic. Examples of Group II-VI semiconductors include, but are not limited to, MgO, MgS, MgSe, MgTe, ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, and HgTe. Acrylic plastic has a relatively low melting point and the upconversion chromophore  104  in contact with the acrylic plastic or embedded within the acrylic plastic would have a reduced risk of heat damage. The waveguide medium  102  may be a solid phase, a liquid phase, a glass phase, or a combination thereof. 
     When the upconversion photoluminescent chromophore  104  absorbs the incident photon  106 , the upconversion photoluminescent chromophore  104  gains energy and enters an excited state. The upconversion photoluminescent chromophore  104  can relax from the excited state to a lower energy state, for example a ground state, by losing energy. One way to lose energy is by emission of an emitted photon  108 . 
     Examples of the upconversion chromophore  104  are, but not limited to, an H-aggregate, a rare-earth ion, a rare-earth ion nanocrystal, a lanthanide chelate and/or a NaYF 4  nanocrystal. Further examples of the upconversion chromophore  104  are, but not limited to, a nanocrystal including neodymium (Nd 3+ ), ytterbium (Yb 3+ ), erbium (Er 3+ ), thulium (Tm 3+ ), holmium (Ho 3+ ), praseodymium (Pr 3+ ), cerium (Ce 3+ ), yttrium (Y 3+ ), samarium (Sm 3+ ), europium (Eu 3+ ), gadolinium (Gd 3+ ), terbium (Tb 3+ ), dysprosium (Dy 3+ ), and/or lutetium (Lu 3+ ). The emitted photon  108  has higher energy than the incident photon  106 . This energy difference is called an anti-Stokes shift. The extra energy may come from dissipation of thermal photons in a crystal lattice. The extra energy may come from the upconversion chromophore  104  absorbing more than one incident photon  106 , each absorbed incident photon  106  having lower energy than the emitted photon  108 . In a two photon process, the upconversion photoluminescent chromophore  104  absorbs two low energy incident photons  106  and emits a single high energy emitted photon  108 . Thus, the upconversion chromophore is configured to absorb a second incident photon after the absorption of the incident photon and then emit the emitted photon, wherein the emitted photon has higher energy than the second incident photon. 
     A significant portion of the solar spectrum is in the infrared range, or wavelength of from 700 nm to 3000 nm. An upconversion chromophore  104  configured to capture at least a portion of this spectrum and upconvert the energy of the captured photon to a useful wavelength for photovoltaic devices, such as wavelength in the visible spectrum, increases overall device efficiency over devices that downconvert ultraviolet spectrum to the visible, and/or near-infrared spectrum. In an embodiment, the upconversion chromophore  104  is configured to absorb the incident photon  106  having a wavelength in infrared range, and then emit the emitted photon  108  having a wavelength in visible range. Infrared range includes near-infrared (NIR), short-wavelength infrared (SWIR), mid-wavelength infrared (MWIR), long-wavelength infrared (LWIR), and far infrared (FIR). In an embodiment, infrared range is wavelength range of from 700 nm to 1,000 μm inclusive. In an embodiment, infrared range is wavelength range of from 700 nm to 1400 nm inclusive. In an embodiment, infrared range is wavelength range of from 700 nm to 3000 nm inclusive. In an embodiment, infrared range is wavelength range of from 1000 nm to 1400 nm inclusive. In an embodiment, infrared range is wavelength range of from 1000 nm to 3000 nm inclusive. In an embodiment, infrared range is wavelength range of from 1400 nm to 3000 nm inclusive. In an embodiment, infrared range is wavelength range of from 3 μm to 8 μm inclusive. In an embodiment, infrared range is wavelength range of from 8 μm to 15 μm inclusive. In an embodiment, infrared range is wavelength range of from 15 μm to 1,000 μm inclusive. 
     Examples of the photovoltaic device  110  are, but not limited to, a photovoltaic cell, quantum dot (QD), a quantum well photovoltaic device, a AlGaAs/GaAs quantum well photovoltaic device, a direct band gap photovoltaic device, a silicon-based photovoltaic device, and/or a Group III-V direct band gap photovoltaic device. 
       FIG. 2  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device  12  that is similar to the upconversion photoluminescent solar concentrator device  10  shown in  FIG. 1 .  FIG. 2  shows the upconversion photoluminescent solar concentrator device  12  including a waveguide  200  and a waveguide medium  202 . A first upconversion photoluminescent chromophore  204  and a second photoluminescent chromophore  206  are in contact with the waveguide medium  202 . The first and second upconversion chromophores  204 ,  206  are each configured to absorb first and second incident photons  208 ,  210 , respectively. The first and second upconversion chromophores  204 ,  206  are each configured to emit first and second emitted photons  212 ,  214 , respectively. First and second emitted photons  212 ,  214  having substantially equal energies for absorption by the photovoltaic device  216 . First and second emitted photons  212 ,  214  each have wavelengths that are within the absorption spectrum range of the photovoltaic device  216 .  FIG. 2  shows the first and second emitted photons  212 ,  214  being directed towards a photovoltaic device  216  by the waveguide  200  for the photovoltaic device  216  for converting the first and second emitted photons  212 ,  214  to electrical energy. A taper may be provided at the interface between the waveguide medium  202  and the photovoltaic device  216 . 
     In an embodiment, the second emitted photon  214  has higher energy than the second incident photon  210 . In an embodiment, the second incident photon  210  has higher energy than the first incident photon  208 . In another embodiment, the first emitted photon  212  and the second emitted photon  214  have the same energy. 
       FIG. 3  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device  14  that is similar to the upconversion photoluminescent solar concentrator device  10  shown in  FIG. 1 . In  FIG. 3 , same labels have been used for identifying structures that are similar to those shown in  FIG. 1 .  FIG. 1  shows the upconversion chromophore  104  embedded in the waveguide medium  102 , and in contact with the waveguide medium  102 .  FIG. 3  shows the upconversion chromophore  104  provided at a surface of the waveguide medium  102 , and in contact with the waveguide medium  102 . 
     When the waveguide medium is a liquid, the upconversion chromophore is suspended in the liquid.  FIGS. 1-3  can be also understood as showing upconversion chromophores suspended in the waveguide medium, wherein the waveguide medium is a liquid. 
       FIG. 4  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device  16  that is similar to the upconversion photoluminescent solar concentrator device  14  shown in  FIG. 3 . In  FIG. 4 , same labels have been used for identifying structures that are similar to those shown in  FIG. 3 . The upconversion photoluminescent solar concentrator device  16  includes a waveguide  100 .  FIG. 4  shows the upconversion chromophore  104  is provided as a film, or a layer  105 , or a sheet, on a surface of the waveguide medium  102 , and in contact with the waveguide medium  102 . For example, the layer  105  is a layer having a plurality of upconversion chromophores  104  applied to a surface of the sol-gel medium  102 . 
       FIG. 5  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device  17 . The upconversion photoluminescent solar concentrator device  17  includes a plurality of waveguides  300 .  FIG. 5  shows three waveguides  300 , wherein the three waveguides  300  are stacked, second waveguide being stacked under the first waveguide, the third waveguide being stacked under the first waveguide. The upconversion photoluminescent solar concentrator device  17  may have more or fewer waveguides. Each of the plurality of waveguides  300  includes a waveguide medium  302 ,  303 ,  304 . The waveguide medium  302 ,  303 ,  304  may be the same material. The waveguide medium  302 ,  303 ,  304  may be different material from each other. Upconversion photoluminescent chromophores  305 ,  306 ,  307  are each in contact with their respective waveguide mediums  302 ,  303 ,  304 . The upconversion chromophores  305 ,  306 ,  307  are each configured to absorb an incident photon  308 ,  309 ,  310 , respectively. The upconversion chromophores  305 ,  306 ,  307  are each configured to emit an emitted photon  311 ,  312 ,  313 , respectively.  FIG. 5  shows each of the emitted photons  311 ,  312 ,  313  being directed towards photovoltaic devices  320 ,  321 ,  322  by the plurality of waveguides  300 . The photovoltaic devices  320 ,  321 ,  322  convert the emitted photons  311 ,  312 ,  313  to electrical energy. One or more tapers may be provided at the interfaces between each and/or all of the waveguide mediums  302 ,  303 ,  304  and the photovoltaic devices  320 ,  321 ,  322 . One or more tapers may be provided at the interfaces between the waveguide mediums  302 ,  303 ,  304 . A reflective surface  330  may be provided on one or more side of the plurality of waveguides  300  for reflecting the emitted photons  311 ,  312 ,  313 . 
       FIG. 6  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device  18  that is similar to the upconversion photoluminescent solar concentrator device  17  shown in  FIG. 5 . In  FIG. 6 , same labels have been used for identifying structures that are similar to those shown in  FIG. 5 .  FIG. 6  shows an embodiment of the upconversion photoluminescent solar concentrator device  18  that has a single photovoltaic device  323  instead of multiple photovoltaic devices  320 ,  321 ,  322  (as shown in  FIG. 5 ).  FIG. 6  shows each of the emitted photons  311 ,  312 ,  313  being directed towards the photovoltaic device  323  by the plurality of waveguides  300 . One or more tapers may be provided at the interfaces between each and/or all of the waveguide mediums  302 ,  303 ,  304  and the photovoltaic device  323 . 
       FIG. 7  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device  19 . The upconversion photoluminescent solar concentrator device  19  includes a plurality of waveguides  400 .  FIG. 7  shows two waveguides  400 , wherein the two waveguides  400  are stacked, second waveguide being under the first waveguide. When a waveguide is said to be under another waveguide, the term under describes being beneath in a direction from a source of an incident photon, so that the incident photon must traverse through the first waveguide before the incident photon enters the waveguide that is under the first waveguide. The upconversion photoluminescent solar concentrator device  19  may have more waveguides stacked together. Each of the plurality of waveguides  400  includes a waveguide medium  402 ,  403 . Upconversion photoluminescent chromophores  405 ,  406  are each in contact with their respective waveguide mediums  402 ,  403 . The upconversion chromophores  405 ,  406  are each configured to absorb an incident photon  408 ,  409 , respectively. The upconversion chromophores  405 ,  406  are each configured to emit an emitted photon  411 ,  412 , respectively.  FIG. 7  shows each of the emitted photons  411 ,  412  being directed towards photovoltaic devices  420 ,  421 ,  422 ,  423  by the plurality of waveguides  400 . Two of the photovoltaic devices  420 ,  422  are provided at opposing end sides of the same waveguide  400 . Two of the photovoltaic devices  421 ,  423  are provided at opposing end sides of the same waveguide  400 . The photovoltaic devices  420 ,  421 ,  422 ,  423  convert the emitted photons  411 ,  412  to electrical energy. One or more tapers may be provided at the interfaces between each and/or all of the waveguide mediums  402 ,  403  and the photovoltaic devices  420 ,  421 ,  422 ,  423 . A reflective surface  440  may be provided on one or more side of the plurality of waveguides  400  for reflecting the emitted photons  411 ,  412  towards the photovoltaic devices  420 ,  421 ,  422 ,  423 . 
       FIG. 8  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device  20  that is similar to the upconversion photoluminescent solar concentrator device  19  shown in  FIG. 7 . In  FIG. 8 , same labels have been used for identifying structures that are similar to those shown in  FIG. 7 .  FIG. 8  shows a single photovoltaic device  425  provided at an end side of the plurality of waveguides  400 , instead of the multiple photovoltaic devices  422 ,  423  (as shown in  FIG. 7 ). The photovoltaic devices  420 ,  421  are provided at opposing end side away from the single photovoltaic device  425 . 
       FIG. 9  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device  21  that is similar to the upconversion photoluminescent solar concentrator device  20  shown in  FIG. 8 . In  FIG. 9 , same labels have been used for identifying structures that are similar to those shown in  FIG. 8 .  FIG. 9  shows a single photovoltaic device  426  provided at an end side of the plurality of waveguides  400 , instead of the multiple photovoltaic devices  420 ,  421  (as shown in  FIGS. 7 and 8 ). The photovoltaic devices  425 ,  426  are provided at opposing end sides of the plurality of waveguides  400 . 
       FIG. 10  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device  22  that is similar to the upconversion photoluminescent solar concentrator device  10  shown in  FIG. 1 . In  FIG. 10 , same labels have been used for identifying structures that are similar to those shown in  FIG. 1 .  FIG. 10  shows the emitted photon  108  being directed towards a photovoltaic device  110  by the waveguide  100 . The embodiment shown in  FIG. 10  includes interface elements between the waveguide  100  and the photovoltaic device  110 .  FIG. 10  shows a taper  500  provided on an antireflection coating  501  at an end side of the waveguide  100 . The antireflection coating  501  is provided on a side of the waveguide at the interface between the taper  500  and the waveguide  100  and/or the waveguide medium  102 . Alternatively, the taper  500  may be provided to be directly in contact with the waveguide  100  and/or the waveguide medium  102 . 
     The refractive index of the taper  500  is higher than a refractive index of the waveguide medium  102 . The photovoltaic device  110  is provided to receive luminescence from the taper  500  side. The photovoltaic device  110  may be directly connected to the taper  500 . Alternatively, the photovoltaic device  110  may be connected to the taper  500  with an antireflection coating provided between the photovoltaic device  110  and the taper  500 . 
     The luminescence hits the exit face of the waveguide  100  at all angles and therefore cannot be further concentrated in the waveguide medium  102  of the same refractive index. However, by including a taper  500  of a transparent medium having higher refractive index than the waveguide medium  102  further concentration of the luminescence to about 5 times is possible, facilitating an overlapping of different units for avoiding shading loss. 
     The taper  500  has an output surface  502  for outputting the emitted photon towards the photovoltaic device  110 , and a receiving surface  503  towards the waveguide for receiving the emitted photon  108 . In an embodiment, the taper  500  has an output surface  502  that is smaller than the receiving surface  503 . The taper  500  may be a nanocrystalline diamond. The taper  500  may be of a material having a refractive index in a range of 2.0 to 2.6 inclusive. A reflective surface  112  may be provided on a second side of the waveguide  100  for reflecting the emitted photon  108  towards the taper  500 . In another embodiment, the upconversion photoluminescent solar concentrator device  22  also includes a photovoltaic device  110  directly connected to the taper  500 , wherein a refractive index of the photovoltaic device  110  is higher than the refractive index of the taper  500 . 
       FIG. 11  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device  23 , wherein the waveguide  100  shown in  FIG. 10  is stacked on top of another waveguide  512 , forming a plurality of waveguides  520 . The second waveguide  512  is under the first waveguide  100 . The second waveguide includes a second upconversion photoluminescent chromophore  504  is in contact with the second waveguide medium  513 . The second upconversion chromophore  504  is configured to absorb a second incident photon  506 . The second upconversion chromophore  504  is configured to emit a second emitted photon  508 .  FIG. 11  shows the second emitted photon  508  being directed towards a second photovoltaic device  510  by the plurality of waveguides  520  for converting the emitted photon  508  to electrical energy.  FIG. 11  shows a second taper  511  provided at an end side of the second waveguide  512 . The antireflection coating may provided on a side of the waveguide at the interface between the taper  511  and the second waveguide  512  and/or the waveguide medium  513 . Alternatively, the taper  511  may be provided to be directly in contact with the second waveguide  512  and/or the waveguide medium  513 .  FIG. 11  shows the second photovoltaic device  510  being provided on the second taper  511  at a surface away from the second waveguide  512 . A taper  514  is provided at the interface between the waveguide mediums  102 ,  513 . 
     The refractive index of the first taper  500  is higher than a refractive index of the first waveguide  100 , the refractive index of the second taper  511  is higher than a refractive index of the second waveguide  512 , and a photovoltaic device connected to the first taper and the second taper. A refractive index of the first photovoltaic device  110  is higher than the refractive index of the first taper  500 . The refractive index of the second photovoltaic device  570  is higher than the refractive index of the second taper  511 . 
       FIG. 12  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device  24  that is similar to the upconversion photoluminescent solar concentrator device  18  shown in  FIG. 6 . In  FIG. 12 , same labels have been used for identifying structures that are similar to those shown in  FIG. 6 .  FIG. 12  shows each of the emitted photons  311 ,  312 ,  313  being directed towards the photovoltaic device  323  by the plurality of waveguides  300 .  FIG. 12  shows a taper  600  being provided at the interfaces between the plurality of waveguides  300  and the photovoltaic device  323 .  FIG. 12  shows a taper  600  provided on an antireflection coating  601  at an end side of the plurality of waveguides  300 . The antireflection coating  601  is provided on a side of the plurality of waveguides  300  at the interface between the taper  600  and the plurality of waveguides  300  and/or the waveguide mediums  302 ,  303 ,  304 . Alternatively, the taper  600  may be provided to be directly in contact with the plurality of waveguides  300  and/or the waveguide mediums  302 ,  303 ,  304 . An antireflection coating may be provided between the taper  323  and the taper  600  therebetween  602 . 
       FIG. 13  shows a perspective view of an embodiment of a waveguide  700  having a rod-like shape axially and a geometric cross-section. 
       FIG. 14  shows a perspective view of another embodiment of a waveguide  702  having a rod-like shape axially and a geometric cross-section. In an embodiment, a height to a width ratio is 1:1000. In an embodiment, a height to a width ratio is 1:&gt;1000. 
       FIG. 15(   a )-( h ) show examples of cross-sectional views for a waveguide. Geometric cross-section allows for efficient stacking of the waveguides.  FIG. 15(   a ) shows a geometric cross-section being a parallelogram.  FIG. 15(   b ) shows a geometric cross-section being a triangle.  FIG. 15(   c ) shows a geometric cross-section being a cross.  FIG. 15(   d ) shows a geometric cross-section being a circle.  FIG. 15(   e ) shows a geometric cross-section being a rectangle.  FIG. 15(   f ) shows a geometric cross-section being a square.  FIG. 15(   g ) shows a geometric cross-section being a hexagon.  FIG. 15(   h ) shows a geometric cross-section being a octagon. 
       FIG. 16  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device  18 ,  24  ( FIGS. 6 and 12 ) and absorption and emission spectrums thereof. The spectrum graph  800  shows Wavelength (λ) vs. Intensity at each of the waveguides. The spectrum graph  800  shows the first absorption spectrum  802  and the first emission spectrum  804  of the first upconversion chromophore  305 , the second absorption spectrum  806  and the second emission spectrum  808  of the second upconversion chromophore  306 , and the third absorption spectrum  810  and the third emission spectrum  812  of the third upconversion chromophore  307 . 
     Incident light of increasing wavelengths  802 ,  806 ,  810  are received by respective waveguides. Upconversion photoluminescent chromophores  304 ,  305 ,  306  tuned to absorb wavelengths of incident radiation  802 ,  806 ,  810  and emit photons  311 ,  312 ,  313  at respective blue-shifted wavelengths  804 ,  808 ,  812 . This blue-shifted radiation  804 ,  808 ,  812  is internally reflected within the respective waveguides and directed towards the photovoltaic device  323 . 
     Substantial overlap is defined to be when an overlap between two spectra is equal to or more than 50%. No substantial overlap is defined to be when an overlap between two spectra is less than 50%. No overlap is defined to be when the overlap between two spectra is less than 90%. 
       FIG. 16  shows that the first absorption spectrum  802  and the first emission spectrum  804  do not substantially overlap, the second absorption spectrum  806  and the second emission spectrum  808  do not substantially overlap, and the third absorption spectrum  810  and the third emission spectrum  812  do not substantially overlap. 
       FIG. 16  shows that the first absorption spectrum  802  and the first emission spectrum  804  do not overlap, the second absorption spectrum  806  and the second emission spectrum  808  do not overlap, and the third absorption spectrum  810  and the third emission spectrum  812  do not overlap. 
       FIG. 16  shows that the first absorption spectrum  802  and the second absorption spectrum  806  do not substantially overlap, and second absorption spectrum  806  and the third absorption spectrum  810  do not substantially overlap.  FIG. 16  shows that the first absorption spectrum  802  and the third absorption spectrum  810  do not overlap. 
       FIG. 16  shows the first emission spectrum  804  and the second emission spectrum  808  having substantial overlap, the second emission spectrum  808  and the third emission spectrum  812  having substantial overlap, and the first emission spectrum  804  and the third emission spectrum  812  having substantial overlap. The first, second, and third emission spectra  804 ,  808 ,  812  overlap with an absorption wavelength of the photovoltaic device  323  for converting radiation to electrical energy. 
       FIG. 17  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device  17  ( FIG. 5 ) and absorption and emission spectrums thereof. The spectrum graph  900  shows Wavelength (λ) vs. Intensity at each of the waveguides. The spectrum graph  900  shows the first absorption spectrum  902  and the first emission spectrum  904  of the first upconversion chromophore  305 , the second absorption spectrum  906  and the second emission spectrum  908  of the second upconversion chromophore  306 , and the third absorption spectrum  910  and the third emission spectrum  912  of the third upconversion chromophore  307 . The first absorption spectrum  902  and the first emission spectrum  904  do not substantially overlap, the second absorption spectrum  906  and the second emission spectrum  908  do not substantially overlap, and the third absorption spectrum  910  and the third emission spectrum  912  do not substantially overlap. The first absorption spectrum  902  and the first emission spectrum  904  do not overlap, the second absorption spectrum  906  and the second emission spectrum  908  do not overlap, and the third absorption spectrum  910  and the third emission spectrum  912  do not overlap. The first absorption spectrum  902  and the second absorption spectrum  906  do not substantially overlap, and second absorption spectrum  906  and the third absorption spectrum  910  do not substantially overlap.  FIG. 16  shows that the first absorption spectrum  902  and the third absorption spectrum  910  do not overlap. The first emission spectrum  904  and the second emission spectrum  908  have no substantial overlap, the second emission spectrum  908  and the third emission spectrum  912  have no substantial overlap, and the first emission spectrum  904  and the third emission spectrum  912  have no substantial overlap. The first, second, and third emission spectra  904 ,  908 ,  912  each overlap with an absorption wavelength of their respective the photovoltaic devices  320 ,  321 ,  322  for converting radiation to electrical energy. Lower layer waveguides of the device  17  absorb and emit sequentially longer wavelengths of light. Upper layer waveguides absorb radiation so that these radiation wavelengths are not significantly seen by lower layers. Thus, effectively, the wavelengths of light absorbed by the upper layer chromophores are “blocked” to the lower layers. The chromophore radiation emission is tuned to the most efficient part of the power conversion spectrum of the corresponding type of photovoltaic device. The superimposed spectrum  920  shows how the device  17  can effectively create an efficient power conversion system. 
       FIG. 18  shows a side view of an embodiment of an upconversion photoluminescent solar concentrator device  25 . The upconversion photoluminescent solar concentrator device  25  includes a first waveguide  930  including a first waveguide medium  932 , a chromophore layer  934  provided on a surface of the first waveguide  930 , the chromophore layer  934  including a plurality of upconversion chromophores  936 ,  938  in contact with the first waveguide medium  932 . A second waveguide  940  is provided above the chromophore layer  934 , wherein the second waveguide  940  includes a second waveguide medium  942 , the plurality of upconversion chromophores  936 ,  938  are in contact with the second waveguide medium  942 . A photovoltaic device  944  is provided at an end side of the first waveguide  930  and the second waveguide  940 .  FIG. 18  shows a taper  946  provided between the photovoltaic device  944  and the first and second waveguides  930 ,  940 . The first waveguide  930  is configured to direct an emitted photon  948  from one of the plurality of the upconversion chromophores  938  entering the first waveguide  930  towards a photovoltaic device  944 . The second waveguide  940  is configured to direct an emitted photon  950  from one of the plurality of the upconversion chromophores  936  entering the second waveguide  940  towards the photovoltaic device  944 . An antireflection coating may be provided on a side of the first and/or the second waveguides  930 ,  940 . The antireflection coating may be provided between the first waveguide  930  and the chromophore layer  934 . The antireflection coating may be provided between the second waveguide  940  and the chromophore layer  934 . The absorption spectrum and the emission spectrum of the plurality of upconversion chromophores  936 ,  938  may overlap, may substantially overlap, and/or completely overlap. The emitted photon  948 ,  950  can be trapped in the waveguide  930 ,  940  that the emitted photon  948 ,  950  enters such that the probability of reabsorption by the upconversion chromophore  936 ,  938  is statistically low, and/or statistically non-existent. Trapping the emitted photon  948 ,  950  in the waveguide  930 ,  940  is achieved by a configuration of the waveguide  930 ,  940  that directs the emitted photon  948 ,  950  in the waveguide  930 ,  940  towards the photovoltaic device  944 . Examples of the configuration are, but not limited to, a geometry of the waveguide  930 ,  940  where in a height to a length ratio of the waveguide being 1:1000, type of waveguide medium  932 ,  942 , refractive index difference between the waveguide medium  932 ,  942  and the chromophore layer  934 , antireflection coating provided between the waveguide  930 ,  940  and the chromophore layer  934 , and/or a combination thereof. 
     Preferred embodiments have been described. Those skilled in the art will appreciate that various modifications and substitutions are possible, without departing from the scope of the invention as claimed and disclosed, including the full scope of equivalents thereof.