Spectrally adaptive multijunction photovoltaic thin film device and method of producing same

Abstract

A method is provided for converting optical energy to electrical energy in a spectrally adaptive manner. The method begins by directing optical energy into a first photovoltaic module that includes non-single crystalline semiconductor layers defining a junction such that a first spectral portion of the optical energy is converted into a first quantity of electrical energy. A second spectral portion of the optical energy unabsorbed by the first module is absorbed by a second photovoltaic module that includes non-single crystalline semiconductor layers defining a junction and converted into a second quantity of electrical energy. The first quantity of electrical energy is conducted from the first module to a first external electrical circuit along a first path. The second quantity of electrical energy is conducted from the second module to a second external electrical circuit along a second path that is in parallel with the first path.

1 . A spectrally adaptive photovoltaic device, comprising:
 a plurality of photovoltaic modules disposed one on top of another, each of the modules including first and second conductive layers and at least first and second semiconductor layers disposed between the conductive layers, said first and second semiconductor layers defining a junction at an interface therebetween;   
       said first and second semiconductor layers of at least one of the modules being non-single crystalline, thin-film layers;
 a substrate on which the plurality of photovoltaic modules are stacked; 
 an insulating layer disposed between adjacent photovoltaic modules; and 
 wherein at least one of the junctions is configured to convert a first spectral portion of optical energy into an electrical voltage and transmit a second spectral portion of optical energy to another of the junctions that is configured to convert the second spectral portion of optical energy into an electrical voltage. 
 
     
     
         2 . A device of  claim 1  wherein the plurality of modules includes at least three modules. 
     
     
         3 . A device of  claim 1  wherein the plurality of junctions collectively have a solar energy conversion efficiency of greater than about 20%. 
     
     
         4 . A device of  claim 1  where at least two of the junctions have semiconductor bandgaps that are different from each other. 
     
     
         5 . A device of  claim 4  where said junction with a smaller bandgap is disposed below another of junction with a larger bandgap and absorbs said second part of optical energy. 
     
     
         6 . A device of  claim 1  where said modules are laterally displaced from one another in part to thereby expose a portion of each of the conductive layers. 
     
     
         7 . A device of  claim 1  where said semiconductor layers comprise CIGS-based semiconductor materials. 
     
     
         8 . A device of  claim 1  where said semiconductor layers comprise Cd-based semiconductor materials. 
     
     
         9 . A device of  claim 1  where said semiconductor layers comprise semiconducting polymers. 
     
     
         10 . A device of  claim 1  where said semiconductor layers comprise nanoparticle composite materials. 
     
     
         11 . A device of  claim 1  where said semiconductor layers comprise organic composite materials. 
     
     
         12 . A device of  claim 1  where said semiconductor layers comprise amorphous semiconductor materials. 
     
     
         13 . A device of  claim 1  wherein the semiconductor layers of at least one of the modules comprise a compound semiconductor material. 
     
     
         14 . A device of  claim 1  where said first and second conductive layers comprise transparent conducting layers. 
     
     
         15 . A device of  claim 1  where said insulating layer comprises a transparent insulating layer. 
     
     
         16 . A device of  claim 1  further comprising a reflecting coating located between a bottommost junction and the substrate. 
     
     
         17 . A device of  claim 1  further comprising a textured surface for scattering unabsorbed part of said optical energy. 
     
     
         18 . A device of  claim 1  wherein a fill factor of a module remote from the substrate is largely independent of a fill factor of a module closer to the substrate. 
     
     
         19 . A device of  claim 1  where said modules are hybridly attached to each other. 
     
     
         20 . A device of  claim 1  where said modules are laminated to each other. 
     
     
         21 . A device of  claim 1  where said modules are bonded to each other. 
     
     
         22 . A device of  claim 1  wherein each module has an area larger than about 400 cm 2 . 
     
     
         23 . A device of  claim 1  further comprising a plurality of electrical voltage converters coupled to the conductive layers for converting different voltages from different junctions to a single common voltage. 
     
     
         24 . A device of  claim 1  wherein a conversion efficiency of the device is less dependent on the spectral content of said optical energy than a corresponding device in which current matching is applicable. 
     
     
         25 . A method for converting optical energy to electrical energy in a spectrally adaptive manner, comprising:
 directing optical energy into a first photovoltaic module that includes non-single crystalline semiconductor layers defining a junction such that a first spectral portion of the optical energy is converted into a first quantity of electrical energy, wherein a second spectral portion of the optical energy unabsorbed by the first module is absorbed by a second photovoltaic module that includes non-single crystalline semiconductor layers defining a junction and converted into a second quantity of electrical energy;   conducting the first quantity of electrical energy from the first module to a first external electrical circuit along a first path; and   conducting the second quantity of electrical energy from the second module to a second external electrical circuit along a second path that is in parallel with the first path.   
     
     
         26 . The method of  claim 25  further comprising independently selecting values of output voltages and currents for each of said photovoltaic modules to enhance their respective individual fill factors, wherein said values of output voltages and currents depend at least on part on a spectral profile of said optical energy. 
     
     
         27 . The method of  claim 25  wherein the plurality of modules collectively have a solar energy conversion efficiency of greater than about 20%. 
     
     
         28 . The method of  claim 25  where the junctions of the first and second modules have semiconductor bandgaps that are different from each other. 
     
     
         29 . The method of  claim 28  where said junction with a smaller bandgap is disposed below another of junction with a larger bandgap and absorbs said second part of optical energy. 
     
     
         30 . A method of forming a spectrally adaptive photovoltaic device, comprising:
 forming on a substrate a first photovoltaic module that includes first and second conductive layers and at least first and second semiconductor layers disposed between the first and second conductive layers, said first and second semiconductor layers defining a first junction at an interface therebetween such that the first junction converts a first spectral portion of optical energy into an electrical voltage;   forming an insulating layer over the first photovoltaic module; and   forming on the insulating layer a second photovoltaic module that includes third and fourth conductive layers and at least third and fourth semiconductor layers disposed between the third and fourth conductive layers, said third and fourth semiconductor layers defining a second junction at an interface therebetween such that the second junction converts a second spectral portion of optical energy into an electrical voltage.   
     
     
         31 . The method of  claim 30  wherein said modules are initially produced on different sacrificial substrates. 
     
     
         32 . The method of  claim 30  further comprising independently selecting values of output voltages and currents for each of said photovoltaic modules to enhance their respective individual fill factors, wherein said values of output voltages and currents depend at least on part on a spectral profile of said optical energy. 
     
     
         33 . The method device of  claim 30  where said modules are hybridly attached to each other. 
     
     
         34 . The method of  claim 30  where said modules are laminated to each other. 
     
     
         35 . The method of  claim 30  where said modules are bonded to each other. 
     
     
         36 . The method of  claim 30  wherein each module has an area larger than about 400 cm 2 . 
     
     
         37 . A method for converting optical energy with a given spectral profile to electrical energy, comprising:
 receiving optical energy on an uppermost module of a photovoltaic device that includes a plurality of modules stacked one on top of another;   converting a first spectral portion of the optical energy to electrical energy, wherein the uppermost module has a first fill factor determined in part by the given spectral profile of the first spectral portion of the optical energy;   transferring a remaining portion of the optical energy to a second module located below the uppermost module; and   converting at least a fraction of the remaining portion of the optical energy to electrical energy, wherein the second module has a second fill factor largely independent of the first fill factor of the uppermost module and determined in part by the given spectral profile of the remaining spectral portion of the optical energy.   
     
     
         38 . The method of  claim 37  wherein the plurality of modules collectively have a solar energy conversion efficiency of greater than about 20%. 
     
     
         39 . The method of  claim 37  where the junctions of the first and second modules have semiconductor bandgaps that are different from each other. 
     
     
         40 . The method of  claim 39  where said junction with a smaller bandgap is disposed below another of junction with a larger bandgap and absorbs said second part of optical energy.