Patent Publication Number: US-10790400-B2

Title: Solar cells that include quantum dots

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of U.S. patent application Ser. No. 14/847,725 filed on Sep. 8, 2015, which is incorporated herein by reference in its entirety. 
    
    
     FIELD 
     The specification relates generally to solar cells, and specifically to solar cells that include quantum dots. 
     BACKGROUND 
     Traditional solar cells are generally designed to function only in daylight and generally absorb light in human visible spectrums, converting the light to electrical energy using semiconductors. However, such solar cells are generally inefficient, typically in the 25-20% range, and furthermore do not function beyond daylight hours. 
     SUMMARY 
     In general, this disclosure is directed to solar cells that include quantum dots in semiconductors that function at the edges of the human visible light range. A first solar cell includes a first set of quantum dots in a first semiconductor, the first semiconductor configured to receive one or more of ambient light and sunlight and emit wavelengths in a near blue range, for example about 450 nm to about 480 nm; the first set of quantum dots are configured to convert these wavelengths to an electrical output. In particular, the first semiconductor can be configured to convert light in the ultraviolet and/or near ultraviolet to the near blue, the ultraviolet and/or near ultraviolet also present at night, for example in starlight, and the like. Hence, the first set of quantum dots receives light in the near blue both in the daytime (e.g. from both the first semiconductor and one or more of ambient light and sunlight) and in the nighttime. Similarly, a second solar cell includes a second set of quantum dots in a second semiconductor, the second semiconductor configured to receive one or more of ambient light and sunlight and emit wavelengths in a red range, close to infrared, for example about 600 nm to about 700 nm; the second set of quantum dots are configured to convert these wavelengths to an electrical output. In particular, the second semiconductor can be configured to convert light in the infrared and/or near infrared to the wavelengths in a red range, the infrared and/or near infrared also present at night, for example in starlight. Hence, the second set of quantum dots receives light in the red both in the daytime (e.g. from both the second semiconductor and one or more of the ambient light and the sunlight) and in the nighttime. Thus, the solar cell functions both in the daytime and in the nighttime. Furthermore, as the solar cell converts light in both a near blue range (e.g. close to the ultraviolet) and a red range (e.g. close to the infrared) to energy, the solar cell generally can mimic the natural process of photosynthesis in an artificial way to convert one or more of ambient light and sunlight into energy. Hence, the solar cell can also comprise a biomimicry device. 
     In this specification, elements may be described as “configured to” perform one or more functions or “configured for” such functions. In general, an element that is configured to perform or configured for performing a function is enabled to perform the function, or is suitable for performing the function, or is adapted to perform the function, or is operable to perform the function, or is otherwise capable of performing the function. 
     It is understood that for the purpose of this specification, language of “at least one of X, Y, and Z” and “one or more of X, Y and Z” can be construed as X only, Y only, Z only, or any combination of two or more items X, Y, and Z (e.g., XYZ, XY, YZ, ZZ, and the like). Similar logic can be applied for two or more items in any occurrence of “at least one . . . ” and “one or more . . . ” language. 
     An aspect of the present specification provides a solar panel comprising: a first solar cell comprising: a first set of quantum dots in a first semiconductor, the first semiconductor configured to receive one or more of ambient light and sunlight and emit first wavelengths a first range of about 450 nm to about 480 nm, the first set of quantum dots configured to convert the first wavelengths to a first electric output; and, a second solar cell comprising: a second set of quantum dots in a second semiconductor, the second semiconductor configured to receive one or more of the ambient light and the sunlight and emit second wavelengths a second range of about 600 nm to about 700 nm, the second set of quantum dots configured to convert the second wavelengths to a second electric output. 
     The first wavelengths can define a spectrum centered in the first range, and the second wavelengths can define a respective spectrum centered in the second range. 
     The first semiconductor can be further configured to convert one or more of ultraviolet (UV) light and near-ultra-violet (NUV) light in one or more of the ambient light and the sunlight to the first wavelengths. 
     The second semiconductor can be further configured to convert one or more of infrared (IR) light and near-IR (NIR) light in one or more of the ambient light and the sunlight to the second wavelengths. 
     The solar panel can further comprise one or more electrical connectors to the first set of quantum dots and the second set of quantum dots, the one or more electrical connectors configured to: convey the first electric output out of the first solar cell; and convey the second electric output out of the second solar cell. 
     The solar panel can further comprise a substrate, the first solar cell and the second solar cell being side-by-side on the substrate. 
     The solar panel can further comprise: a substrate; a plurality of first solar cells, including the first solar cell, each of the plurality of first solar cells similar to the first solar cell; and, a plurality of second solar cells, including the second solar cell, each of the plurality of second solar cells similar to the second solar cell, the plurality of first solar cells and the plurality of second solar cells arranged on the substrate. 
     The solar panel can further comprise a substrate, the second solar cell located on the substrate, and the first solar cell located on the second solar cell, the first solar cell being transparent to the second wavelengths. 
     The solar panel can further comprise a substrate, the first solar cell located on the substrate, and the second solar cell located on the first solar cell, the second solar cell being transparent to the first wavelengths. 
     The first solar cell and the second solar cell can be stacked on each other and on a substrate, an outer solar cell, of the first solar cell and the second solar cell, can be transparent to respective wavelengths associated with an inner solar cell, of the first solar cell and the second solar cell. The substrate can be transparent and the inner solar cell can be transparent to respective associated wavelengths of the outer solar cell. 
     The first semiconductor can comprise one or more of: GaN, InGaN, and AlGaN, and the second semiconductor can comprise one or more of: InGaN, AlInGaN, and InGaAlP. 
     The first set of quantum dots can be doped with one or more of: Si, Ge, Cr, S, Fe, Mn, Zn, and the second set of quantum dots can be doped with one or more of Mg, Be, Ba, Cr, Al, Fe. 
     The first set of quantum dots can be doped with an N-type material with absorption in the first range, and the second set of quantum dots can be doped with a P-type material with absorption in the second range. 
     The first semiconductor can comprise In x Ga (1-x) N, where x can be in a range of about 0.0 to about 0.10. 
     The second semiconductor can comprise In x Ga (1-x) N, where x can be in a range of about 0.60 In to about 0.75. 
     The second semiconductor can comprise materials configured to convert infrared light to the second wavelengths in the second range. 
     The solar panel can further comprise one or more lenses configured to convey one or more of the ambient light and the sunlight into the first solar cell and the second solar cell. 
     The solar panel of claim  1 , wherein one or more of the first semiconductor and the second semiconductor can be in a shape of one or more lenses configured to convey the one or more of the ambient light and sunlight into a respective solar cell. 
     The solar panel can further comprise one or more reflective layers arranged to reflect one or more of the ambient light and the sunlight passing through one or more of the first solar cell and the second solar cell back through one or more one or more of the first solar cell and the second solar cell. 
     A further aspect of the present specification provides a solar cell comprising: a first set of quantum dots in a first semiconductor, the first semiconductor configured to receive one or more of ambient light and sunlight and emit first wavelengths, the first set of quantum dots configured to convert the first wavelengths to a first electric output; at least one quantum dot in the first set of quantum dots being coated by a first reflective layer; the first reflective layer being coated by a first layer of the first semiconductor; and the first layer of the first semiconductor being coated by a second reflective layer, the second reflective layer meeting the first reflective layer to enclose the first layer of the first semiconductor between the first reflective layer and the second reflective layer. 
     The first set of quantum dots can extend from a surface, and the first reflective layer and the second reflective layer can meet one another at the surface. 
     A maximum height of the first reflective layer measured from the surface can be about two-thirds a corresponding maximum height of the second reflective layer measured from the surface. 
     The second reflective layer can be at least partially transparent to a given portion of the one or more of ambient light and sunlight, the given portion being absorbable by the first semiconductor; and the first reflective layer can be at least partially transparent to the first wavelengths and at least partially reflective of the given portion. 
     The first layer of the first semiconductor can be substantially crescent-shaped in cross-section. 
     A further aspect of the present specification provides a solar panel comprising: a first solar cell comprising: a first set of quantum dots in a first semiconductor, the first semiconductor configured to receive one or more of ambient light and sunlight and emit first wavelengths in a first range of about 450 nm to about 480 nm, the first set of quantum dots configured to convert the first wavelengths to a first electric output; and a second solar cell comprising: a second set of quantum dots in a second semiconductor, the second semiconductor configured to receive one or more of the ambient light and the sunlight and emit second wavelengths a second range of about 600 nm to about 700 nm, the second set of quantum dots configured to convert the second wavelengths to a second electric output; wherein one or more of: at least one quantum dot in the first set of quantum dots is coated by a first reflective layer; the first reflective layer is coated by a first layer of the first semiconductor; and the first layer of the first semiconductor is coated by a second reflective layer, the second reflective layer meeting the first reflective layer to enclose the first layer of the first semiconductor between the first reflective layer and the second reflective layer; and; at least one quantum dot in the second set of quantum dots is coated by a corresponding first reflective layer; the corresponding first reflective layer is coated by a corresponding first layer of the second semiconductor; and the corresponding first layer of the second semiconductor is coated by a corresponding second reflective layer, the corresponding second reflective layer meeting the corresponding first reflective layer to enclose the corresponding first layer of the second semiconductor between the corresponding first reflective layer and the corresponding second reflective layer. 
     The first semiconductor can be configured to absorb at least a first portion of the one or more of ambient light and sunlight and in response emit the first wavelengths in the first range, the first portion having a respective wavelength smaller than about 450 nm, the first set of quantum dots doped with an N-type material with absorption in the first range; and the second semiconductor can be configured to absorb at least a second portion of the one or more of ambient light and sunlight and in response emit the second wavelengths in the second range, the second portion having a respective wavelength larger than about 700 nm, the second set of quantum dots doped with a P-type material with absorption in the second range; the first range and the second range comprising wavelength ranges used in photosynthesis. 
     The solar panel can further comprise: a substrate, wherein the first solar cell and the second solar cell are side-by-side on the substrate in a planar arrangement such that a respective top surface of each of the first solar cell and the second solar cell receives one or more of the ambient light and the sunlight without the one or more of the ambient light and the sunlight first passing through the other of the first solar cell and the second solar cell. 
     The first wavelengths can define a spectrum centered in the first range, and the second wavelengths can define a respective spectrum centered in the second range. 
     One or more of: the first semiconductor can be further configured to convert one or more of ultraviolet (UV) light and near-ultra-violet (NUV) light in one or more of the ambient light and the sunlight to the first wavelengths; and the second semiconductor can be further configured to convert one or more of infrared (IR) light and near-IR (NIR) light in one or more of the ambient light and the sunlight to the second wavelengths. 
     The solar panel can further comprise one or more electrical connectors to the first set of quantum dots and the second set of quantum dots, the one or more electrical connectors configured to: convey the first electric output out of the first solar cell; and convey the second electric output out of the second solar cell. 
     The solar panel can further comprise: a substrate; a plurality of first solar cells, including the first solar cell, each of the plurality of first solar cells similar to the first solar cell; and, a plurality of second solar cells, including the second solar cell, each of the plurality of second solar cells similar to the second solar cell, the plurality of first solar cells and the plurality of second solar cells arranged on the substrate. 
     One of: the first semiconductor can comprise one or more of: GaN, InGaN, and AlGaN and the second semiconductor can comprise one or more of: InGaN, AlInGaN, and InGaAlP; and the first set of quantum dots can be doped with one or more of: Si, Ge, Cr, S, Fe, Mn, Zn, and the second set of quantum dots can be doped with one or more of Mg, Be, Ba, Cr, Al, Fe. 
     One or more of: the first semiconductor can comprise In x Ga (1-x) N, where x is in a range of about 0.0 to about 0.10; and the second semiconductor can comprise In x Ga (1-x) N, where x is in a range of about 0.60 to about 0.75. 
     The second semiconductor can comprise materials configured to convert infrared light to the second wavelengths in the second range. 
     The solar panel can further comprise one or more respective lenses on the respective top surface of each of the first solar cell and the second solar cell, the one or more respective lenses configured to convey one or more of the ambient light and the sunlight into the first solar cell and the second solar cell. 
     The respective top surface of each of the first semiconductor and the second semiconductor can be in a shape of one or more respective lenses configured to convey the one or more of the ambient light and sunlight into a respective solar cell. 
     The solar panel can further comprise one or more additional reflective layers arranged to reflect one or more of the ambient light and the sunlight passing through one or more of the first solar cell and the second solar cell back through one or more of the first solar cell and the second solar cell. 
     The corresponding second reflective layer can be at least partially transparent to a given portion of the one or more of ambient light and sunlight, the given portion being absorbable by the second semiconductor; and the corresponding first reflective layer can be at least partially transparent to the second wavelengths and at least partially reflective of the given portion. 
     The corresponding first layer of the second semiconductor can be substantially crescent-shaped in cross-section. 
    
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
       For a better understanding of the various implementations described herein and to show more clearly how they may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which: 
         FIG. 1  depicts a solar panel that includes quantum dots in semiconductors, according to non-limiting implementations. 
         FIG. 2  depicts operation of a portion of the solar panel of  FIG. 1 , according to non-limiting implementations. 
         FIG. 3  depicts further details of the operation of the portion of  FIG. 2 , according to non-limiting implementations. 
         FIG. 4  depicts operation of another portion of the solar panel of  FIG. 1 , according to non-limiting implementations. 
         FIG. 5  depicts further details of the operation of the portion of  FIG. 3 , according to non-limiting implementations. 
         FIG. 6  depicts a solar panel that includes quantum dots in semiconductors, according to alternative non-limiting implementations. 
         FIG. 7  depicts a solar panel that includes quantum dots in semiconductors and stacked solar cells, according to alternative non-limiting implementations. 
         FIG. 8  depicts a solar panel that includes quantum dots in semiconductors and stacked solar cells, according to alternative non-limiting implementations. 
         FIG. 9  depicts a solar panel that includes quantum dots in semiconductors, optional lenses, and optional reflective layers, according to alternative non-limiting implementations. 
         FIG. 10  depicts a solar panel that includes quantum dots in semiconductors shaped into one or more lenses, and optional reflective layers, according to alternative non-limiting implementations. 
         FIG. 11  depicts a solar cell that includes quantum dots in semiconductors, and reflective layers forming optical cavities adjacent quantum dots, according to alternative non-limiting implementations. 
         FIG. 12  depicts another solar cell that includes quantum dots in semiconductors, and reflective layers forming optical cavities adjacent quantum dots, according to alternative non-limiting implementations. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  depicts a solar panel  100  comprising: a first solar cell  101  comprising: a first set of quantum dots  111  in a first semiconductor  113 , first semiconductor  113  configured to receive one or more of ambient light and sunlight and emit first wavelengths a first range of about 450 nm to about 480 nm, first set of quantum dots  111  configured to convert the first wavelengths to a first electric output; and, a second solar cell  102  comprising: a second set of quantum dots  112  in a second semiconductor  115 , second semiconductor  115  configured to receive one or more of the ambient light and the sunlight and emit second wavelengths a second range of about 600 nm to about 700 nm, second set of quantum dots  112  configured to convert the second wavelengths to a second electric output. In particular  FIG. 1  depicts a cross-sectional view of solar panel  100 ; hence while only one row of quantum dots  111  and one row of quantum dots  112  are depicted, each set of quantum dots  111 ,  112  can be arranged in a two-dimensional array, and/or in a regular two-dimensional structure and/or in a random two-dimensional structure in solar panel  100 . In some implementations, the second range can comprise about 630 nm to about 700 nm; in other implementations, the second range can comprise about 630 nm to about 690 nm; in yet further implementations, the second range can comprise about 630 nm to about 680 nm. 
     Additionally, a depicted shape of quantum dots  111 ,  112  is merely meant to be schematic, and quantum dots  111 ,  112  can be in suitable shape, for example, as circles, rectangles, mesas, and the like. 
     Furthermore, in some implementations, one or more of first solar cell  101  and second solar cell  102  can comprise a stack of respective semiconductors and respective quantum dots. For example, while as depicted first solar cell  101  comprises one layer of first semiconductor  113  and one set of quantum dots  111 , in other implementations, the semiconductor  113 /quantum dots  111  structure can be repeated to increase the overall efficiency of first solar cell  101 . Alternatively, first solar cell  101  can comprise a layer of first semiconductor  113  and stacks of layers of quantum dots. Similar structures can be present in second solar cell  102 , using second semiconductor  115  and quantum dots  112 . 
     As depicted in  FIG. 1 , solar panel  100  further comprises a substrate  120  which can be transparent and/or partially transparent to sunlight, ambient light, and starlight (or other sources of light present at night) and the like, opaque or translucent. When transparent (and/or partially transparent and/or translucent), sunlight, ambient light and light from radiative sources present at night (such as starlight, skyglow, moonlight, etc.) can generally be received from both sides of solar panel  100 . For example, substrate  120  can comprise one or more of silicon, glass, plastic, metal and the like. Other types of substrate materials for solar cells are within the scope of present implementations and will occur to persons of skill in the art. 
     As also depicted in  FIG. 1 , solar panel  100  can further comprise one or more electrical connectors  121 ,  122  to first set of quantum dots  111  and second set of quantum dots  112 , one or more electrical connectors  121 ,  122  configured to: convey the first electric output out of first solar cell  101 ; and convey the second electric output out of the second solar cell  102 . For example, electrical connector  121  is in connector with first set of quantum dots  111  and electrical connector  122  is in connector with second set of quantum dots  112 . Alternatively, solar panel  100  can include one electrical connector that connects to both sets of quantum dots  111 ,  112 , or a plurality of electrical connectors that connect to subsets of quantum dots  111 ,  112 . As depicted, one or more electrical connectors  121 ,  122  comprise a thin film layer between each of solar cells  101 ,  102  and substrate  120 . For example, electrical connectors  121 ,  122  can comprise a conducting metallic layer such as aluminum, gold, platinum, and the like. In addition, electrical connectors  121 ,  122  can comprise a transparent and/or partially transparent material including, but not limited to, indium tin oxide (ITO) and the like; for example, when substrate is transparent and/or partially transparent, electrical connectors  121 ,  122  can also be transparent and/or partially transparent. Furthermore, electrical connectors  121 ,  122  can be located at other positions in solar panel  100  that convey electrical output out of solar cells  101 ,  102 , as will occur to persons of skill in the art. 
     Operation of first solar cell  101  in daylight is now described with reference to  FIG. 2 , which depicts first solar cell  101  independent of second solar cell  102 . In particular, in  FIG. 1 , first solar cell  101  and second solar cell  102  are side-by-side and/or adjacent on substrate  120 , however in  FIG. 2 , first solar cell  101  is depicted without second solar cell  102 , but solar cell  102  is nonetheless appreciated to be present in  FIG. 2 . 
     Also depicted in  FIG. 2  is the sun  200  and a graph of radiation from the sun  200  as a function of wavelength, including a curve of standard air-mass zero (“AM0”) radiation from the sun  200 , and a curve of air-mass 1.5 atmosphere (“AM1.5”), each in relative units, with AM1.5 generally being used as the standard within the solar panel industry. Furthermore, a range  201  of about 300 nm to about 400 nm (which can also be referred to as a near-ultra-violet (“NUV”) range) is indicated under the AM1.5 curve, as well as a range  202  of about 450 nm to about 480 nm (which can also be referred to as a near-blue range). In addition, while the following figures are discussed with respect to light emitted from the sun  200 , it is appreciated that light conversion as described herein can occur for any form of ambient light to which solar panel  100  is exposed. 
     In general, semiconductor  113  is selected such that at least a portion of light  211  (e.g. with wavelengths in range  201 ) of sunlight  210  that irradiates semiconductor  113  is converted to light  213 - 1  of wavelengths in range  202 . Not all of sunlight  210  is necessarily converted to light  213 - 2 ; for example, semiconductor  113  can be selected such that the wavelengths converted by semiconductor  113  to light  213 - 1  define a spectrum centered in first range  201 , for example, a Gaussian-shaped spectrum and the like. Indeed, semiconductor  113  can be sensitive to wavelengths outside of first range  201 , but with a conversion spectrum centred (and/or near-centered) in first range  201 . 
     For example, semiconductor  113  can comprise a semiconductor system where a bandgap and/or intermediate levels are selected and/or adjusted by way of materials selection and/or doping and/or selection of materials for quantum dots  111  such that light in range  201  is converted to light  213 - 1  in range  202 ; as such, electrons in semiconductor  113  are excited by light  213 - 1  in range  201  (e.g. from sunlight  210 ) and, excited electrons can relax to an intermediate level in where light  213 - 1  in range  202  is emitted. Furthermore, a size, spacing and the like of quantum dots  111  can also affect the bandgap and/or intermediate levels of semiconductor  113 . Hence, semiconductor  113  and quantum dots  111  together comprise a wavelength and/or energy conversion system that converts light in the ultraviolet and/or near ultraviolet range to light in the near-blue range. However, in other implementations, semiconductor  113  can be configured to convert other wavelength ranges to the near-blue range, including light in ranges lower than range  201 , and light in ranges higher than range  201  (including light in ranges higher than range  202 ). 
     As depicted, materials and/or size of first set of quantum dots  111  are selected to convert at least a portion of light  213 - 1  in range  202  to produce an electrical output  250 , which can be extracted from first solar cell  101  via electrical connector  121 , as well to select the bandgap and/or intermediate levels of semiconductor  113 . It is noted that light in range  202  is received at first set of quantum dots  111  both from light  213 - 1  emitted by semiconductor  113  during the conversion process and from light  213 - 2  in range  202  in sunlight  210 . Light  213 - 1 ,  213 - 2  in range  202  will hence interchangeably be referred to hereafter as light  213 . 
     As a size and/or materials of first set of quantum dots  111  are selected to convert light  213  in range  202  to electrical output  250 , and as quantum dots can, in general, be precisely tuned, the overall efficiency of the conversion rate of light  213  in range  202  can be increased by converting light  211  in range  201  to light  213  in range  202  by semiconductor  113 , as also indicated by arrow  290 . Furthermore, as there is background ambient ultraviolet radiation at night (for example from skyglow, light pollution, zodiacal light, starlight, etc.) first solar cell  101  will also generate electrical output at night. 
     A remainder  271  of sunlight  210  can pass through semiconductor  113  and quantum dots  111 , presuming that semiconductor  113  and quantum dots  111  are transparent to wavelengths of light outside of ranges  201 ,  202 . In other words, remainder  271  can comprise wavelengths of sunlight  210  with at least a portion of light  211 ,  213  in wavelength ranges  201 ,  202  absorbed by semiconductor  113  and/or quantum dots  111 . 
     The conversion process is described in further detail with reference to  FIG. 3 , which depicts semiconductor  113  having a bandgap  301 , with an intermediate level  302 , as well as a quantum dot  111  having an associated bandgap  303 ; furthermore, while only one quantum dot  111  is depicted, it is appreciated that first set of quantum dots  111  is present and that a size of bandgap  301  and/or a position of intermediate level  302  can at least partially arise from, and/or be influence by, a size &amp; spacing of a plurality of quantum dots  111 . Bandgap  301  is selected such that electrons of semiconductor  113  are excited across bandgap  301  by light  211 ; electrons are not labelled in  FIG. 3 , but are depicted as shaded circles. Electrons excited across bandgap  301  then relax to intermediate level  302 , such that light  213 - 1  is emitted by semiconductor  113 . While not depicted, electrons can then relax to the bottom of bandgap  301 . Light  213 - 1  emitted by semiconductor  113  interacts with electrons in quantum dot  111 , and bandgap  303  is selected such that electrons of quantum dot  111  are excited across bandgap  303  by light  213 - 1  (and/or by light  213 - 2  from sunlight, and the like); indeed, bandgap  303  is selected such that electrons are excited out of quantum dot  111  thereby generating electrical output  250 . Similarly, intermediate level  302  is selected to produce light  213 - 1  compatible with bandgap  303 . A similar process occurs during the nighttime due to UV radiation present at night from sources described above. 
     Operation of second solar cell  102  in daylight is now described with reference to  FIG. 4 , which depicts second solar cell  102  independent of second solar cell  101 . In particular, in  FIG. 1 , first solar cell  101  and second solar cell  102  are side-by-side and/or adjacent on substrate  120 , however in  FIG. 4 , second solar cell  102  is depicted without first solar cell  101 , but first solar cell  101  is nonetheless appreciated to be present in  FIG. 4 . 
     Also depicted in  FIG. 4  are the sun  200  and the graph of radiation from the sun  200  as depicted in  FIG. 2 . Furthermore, a range  401  of about 800 nm to about 900 nm (which can also be referred to as a near-infrared (“NIR”) range) is indicated under the AM1.5 curve, as well as a range  402  of about 600 nm to about 700 nm. However, in other implementations, range  402  can comprise about 630 nm to about 700 nm; in further implementations, range  402  can comprise about 630 nm to about 690 nm; in yet further implementations, range  402  can comprise about 630 nm to about 680 nm. 
     In general, semiconductor  115  is selected such that at least a portion of light  411  (e.g. with wavelengths in range  401 ) of sunlight  210  that irradiates semiconductor  115  is converted to light  413 - 1  of wavelengths in range  402 . Not all of sunlight  210  is necessarily converted to light  413 - 2 ; for example, semiconductor  115  can be selected such that the wavelengths converted by semiconductor  115  to light  413 - 2  define a spectrum centered in first range  401 , for example, a Gaussian-shaped spectrum and the like. Indeed, semiconductor  115  can be sensitive to wavelengths outside of first range  401 , but with a conversion spectrum centred (and/or near-centered) in first range  401 . 
     For example, semiconductor  115  can comprise a semiconductor system where a bandgap and/or intermediate levels are selected and/or adjusted by way of materials selection and/or doping and/or selection of materials for quantum dots  112  such that light in range  401  is converted to light  411  in range  402 ; as such, electrons in semiconductor  115  are excited by light in range  401  (e.g. from sunlight  210 , and the like) and, excited electrons can relax to an intermediate level in where light  411  in range  402  is emitted. Furthermore, a size, spacing and the like of quantum dots  112  can also affect the bandgap and/or intermediate levels of semiconductor  115 . Hence, semiconductor  115  and quantum dots  112  together comprise a wavelength and/or energy conversion system that converts light in the infrared and/or near infrared range to light in the red range. Such down conversion of wavelengths of light (and/or up conversion of energy) can occur when two or more low-energy (e.g. sub-bandgap) photons are combined into a higher energy photon. However, in other implementations, semiconductor  115  can be configured to convert other wavelength ranges to the red range, including light in ranges higher than range  401 , and light in ranges lower than range  401  (including light in ranges lower than range  402 ). 
     As depicted, materials and/or size of second set of quantum dots  112  are selected to convert at least a portion of light  413 - 1  in range  402  to produce an electrical output  450 , which can be extracted from second solar cell  102  via electrical connector  122 . It is noted that light in range  402  is received at second set of quantum dots  112  both from light  413 - 2  in range  402  in sunlight  210  and light  413 - 1  emitted by semiconductor  115  during the conversion process. Light  413 - 1 ,  413 - 2  in range  402  will hence interchangeably be referred to hereafter as light  413 . 
     As a size and/or materials of second set of quantum dots  112  are selected to convert light  413  in range  402  to electrical output  450 , and as quantum dots can, in general, be precisely tuned, the overall efficiency of the conversion rate of light  413  in range  402  can be increased by converting light  411  in range  401  to light  413  in range  402  by semiconductor  115 , as also indicated by arrow  490 . Furthermore, as there is background ambient infrared radiation at night (for example from skyglow, light pollution, zodiacal light, starlight, etc.) second solar cell  102  will also generate electrical output at night. 
     A remainder  471  of sunlight  210  can pass through semiconductor  115  and quantum dots  112 , presuming that semiconductor  115  and quantum dots  112  is transparent to wavelengths of light outside of ranges  401 ,  402 . In other words, remainder  471  can comprise wavelengths of sunlight  210  with at least a portion of light in wavelength ranges  401 ,  402  absorbed by semiconductor  115  and/or quantum dots  112 . 
     The conversion process is described in further detail with reference to  FIG. 5 , which depicts semiconductor  115  having a bandgap  501 , with an intermediate level  502 , as well as a quantum dot  112  having an associated bandgap  503 ; furthermore, while only one quantum dot  112  is depicted, it is appreciated that second set of quantum dots  112  is present and that a size of bandgap and/or a position of intermediate levels  502  (and an intermediate level  505 , described below) can at least partially arise from, and/or be influence by, a size &amp; spacing of a plurality of quantum dots  112 . Bandgap  501  is selected such that electrons of semiconductor  115  are excited across bandgap  501  by light  411 ; electrons are not labelled in  FIG. 5 , but are depicted as shaded circles. For example, electrons can absorb two photons of light  411 , a first photon at a bottom of bandgap  501  where the electron is excited to another intermediate level  505 , and a second photon to another intermediate level  505 . While the process as described herein is simplified for clarity, such a process can be referred to as down conversion of light (and/or up conversion of energy) and occur when two or more low-energy (e.g. sub-bandgap) photons are combined into a higher energy photon. 
     For example, electrons excited across bandgap  501  then relax to intermediate level  502 , such that light  413 - 1  is emitted by semiconductor  115 . While not depicted, electrons can then relax to the bottom of bandgap  501 . Light  413 - 1  emitted by semiconductor  115  interacts with electrons in quantum dot  112 , and bandgap  503  is selected such that electrons of quantum dot  112  are excited across bandgap  503  by light  413 - 1  (and/or by light  413 - 2  from sunlight, and the like); indeed, bandgap  503  is selected such that electrons are excited out of quantum dot  112  thereby generating electrical output  450 . Similarly, intermediate level  502  is selected to produce light  413 - 1  compatible with bandgap  503 . A similar process occurs during the nighttime due to infrared radiation present at night from sources described above. 
     In particular, it is known that the night sky is a relatively large source of infrared radiation at least in the near infrared red range. Hence, at least solar cell  102  will operate at night, as well as in daytime, as light  411  in range  401  is converted to light  413 - 1  by semiconductor  115 , which is in turn converted to electrical output  450  by quantum dots  112 . 
     Hence, returning to  FIG. 1 , solar panel  100  comprises first solar cell  101  and second solar cell  102  arranged side-by-side on substrate  120 . Furthermore, as described with reference to  FIG. 2 , first semiconductor  113  can be further configured to convert one or more of ultraviolet (UV) light and near-ultra-violet (NUV) light in sunlight, and the like, to first wavelengths in a first range  201 , and, as described with reference to  FIG. 3 , second semiconductor  115  is further configured to convert one or more of infrared (IR) light and near-IR (NIR) light in the sunlight, and the like, to the second wavelengths in a second range  402 . Hence, solar panel  100  generally operates in four wavelength ranges: the ultraviolet (and/or NUV), the near-blue, the red, and the infrared (and/or NIR); furthermore light in the ultraviolet (and/or NUV) and the infrared (and/or NIR) is converted to respective light near the opposite edges of the visible spectrum (e.g. in the human visual system (“HVS”)), where it is converted to an electrical output. 
     Indeed, solar panel  100  generally converts energy in the ultraviolet (and/or NUV) to the near-blue, and energy in the infrared (and/or NIR) to the red. Put another way, charge transfer occurs from semiconductor  113  to quantum dots  111  when semiconductor  113  is excited by sunlight and/or ambient light, and charge transfer occurs from semiconductor  115  to quantum dots  112  when semiconductor  115  is excited by sunlight and/or ambient light. Indeed, such charge transfer can occur by mechanisms other than each of semiconductors  113 ,  115  emitting respective light; rather, each of semiconductors  113 ,  115  can emit charge which is collected by respective quantum dots  111 ,  112  and/or quanta of energy emitted by each of semiconductors  113 ,  115  can be used to excite respective quantum dots  111 ,  112 . 
     Furthermore, as solar panel  100  can convert light in the near-blue and red wavelength ranges to energy other than light energy (e.g. a respective electrical output), solar panel  100  can also be viewed as a system that mimics photosynthesis, exploiting similar wavelength ranges as, for example, chlorophyll A, and the like. Hence, solar panel  100  can also comprise a biomimicry system that mimics, at least in part, the energy conversion processes of photosynthesis in leaves, for example. 
     Solar panel  100  can further comprise various materials systems to achieve the desired energy conversion. For example, in some implementations, first semiconductor  113  can include, but is not limited to, one or more of: GaN, InGaN, AlGaN and the like; and second semiconductor  115  can include, but is not limited to, one or more of: InGaN, AlInGaN, InGaAlP, and the like. In each of semiconductors  113 ,  115 , ratios and/or compositions of materials are selected according to the desired respective bandgap, as will occur to persons of skill in the art. 
     Furthermore, first set of quantum dots  111  can be doped with an n-type material with absorption in second range  202 , including, but not limited to, one or more of Si, Ge, Cr, S, Fe, Mn, Zn and the like; and second set of quantum dots  112  can be doped with a p-type material with absorption in second range  402 , including, but not limited to, one or more of Mg, Be, Ba, Cr, Al, Fe and the like. 
     In particular non-limiting implementations, first semiconductor  113  can comprise In x Ga (1-x) N, where x in a range of about 0.0 to about 0.10 (e.g. when x=0, semiconductor  113  comprises GaN), as well as one or more appropriate dopants, such as Si. In further particular non-limiting implementations, second semiconductor  115  comprises In x Ga (1-x) N, where x in a range of about 0.60 In to about 0.75. In general, in each of these implementations, each semiconductor  113 ,  115  can be doped with one or more materials that adjusts respective bandgaps, and/or introduces intermediate levels, that enable operation to each semiconductor  113 ,  115  as described above. 
     However, for the above described conversion from infrared to red light with respect to  FIG. 5 , second semiconductor  115  can comprise various “upconverter” materials and/or systems including, but not limited to, NaYF 4 :(Er,Yb), BaCl 2 :(Er 3+ ,Dy 3+ ), and the like. Indeed, any material which can convert infrared and/or near infrared light to red light is within the scope of present implementations. 
     Similarly, for the above described conversion from ultraviolet to blue light with respect to  FIG. 3 , first semiconductor  113  can comprise various “downconverter” materials and/or systems. Indeed, any material which can convert ultraviolet and/or near ultraviolet light to blue light is within the scope of present implementations. 
     Similarly, one or more of a size and material of each set of quantum dots  111 ,  112  are selected such that each set of quantum dots  111 ,  112  converts light in a respective range to an electrical output. 
     In  FIG. 1 , first solar cell  101  and second solar cell  102  are adjacent one another on substrate  120 ; for example, each of solar cells  101 ,  102  can occupy about half of an area of substrate. However, other implementations are within the scope of present implementations. 
     For example, attention is next directed to  FIG. 6  which depicts a solar panel  600  that is substantially similar to solar panel  100 , with like elements having like numbers, however in a “600” series rather than a “100” series. In particular, solar panel  600  comprises a substrate  620 ; a plurality of first solar cells  601  (which can include first solar cell  101 ), each of plurality of first solar cells  601  similar to first solar cell  101 ; a plurality of second solar cells  602  (which can include second solar cell  602 ), each of plurality of second solar cells  602  similar to second solar cell  102 , plurality of first solar cells  601  and plurality of second solar cells  602  arranged on substrate  620 . While not depicted in  FIG. 6 , it is assumed that each of plurality of first solar cells  601  comprises a set of quantum dots and a semiconductor similar, respectively, to first set of quantum dots  111  and semiconductor  113 , and that each of plurality of second solar cells  602  comprises a set of quantum dots and a semiconductor similar, respectively, to second set of quantum dots  112  and semiconductor  115 . It is further assumed that solar panel  600  comprises one or more electrical connectors similar to one or more of electrical connectors  121 ,  122 . 
     As depicted, solar cells  601  alternate with solar cells  602 , however solar cells  601 ,  602  can be arranged in any suitable pattern on substrate  620 . 
     Persons skilled in the art will appreciate that there are yet more alternative implementations and modifications possible, and that the above examples are only illustrations of one or more implementations. 
     For example, attention is next directed to  FIG. 7 , which depicts a solar panel  700  that is substantially similar to solar panel  100 , with like elements having like numbers, however in a “700” series rather than a “100” series. In particular, solar panel  700  comprises a substrate  720 , a first solar cell  701  and a second solar cell  702 . As also depicted in  FIG. 7 , first solar cell  701  comprises a respective set of quantum dots  711  and a respective semiconductor  713 , similar, respectively, to first set of quantum dots  111  and semiconductor  113 ; and second solar cell  702  comprises a respective set of quantum dots  712  and a respective semiconductor  715 , similar, respectively, to second set of quantum dots  112  and semiconductor  115 . 
     Second solar cell  702  located on substrate  720 , and first solar cell  701  is located on second solar cell  702  (e.g. second solar cell  702  is between substrate  720  and first solar cell  701 ). In general, first solar cell  701  is transparent to wavelengths that are absorbed by second solar cell  702  and/or wavelengths that are converted by second solar cell  702  to an electrical output, such that wavelengths (for example in sunlight, and the like) to which second solar cell  702  are sensitive, pass through first solar cell  701  to reach second solar cell  702 . Similarly, when substrate  720  is transparent, second solar cell  702  is transparent to wavelengths that are absorbed by first solar cell  701  and/or wavelengths that are converted by first solar cell  701  to an electrical output, such that wavelengths (for example in sunlight, and the like) to which first solar cell  701  are sensitive, pass through second solar cell  702  to reach first solar cell  701 . Furthermore, ratios and/or compositions materials of semiconductors  713 ,  715  can be graded, for example near the interface there between, and/or semiconductors  713 ,  715  can each comprises layers of materials of different ratios and/or different compositions materials of semiconductors  713 ,  715 , for example near the interface there between. Such grading and/or formation of layers of different ratios can occur during manufacture of semiconductors  713 ,  715  to assist in achieving target ratios in each of semiconductors  713 ,  715 . 
     Solar panel  700  further comprises electrical connectors  721 ,  722 , electrical connectors  721  configured to convey an electrical output from first set of quantum dots  711  out of solar panel  700 , and electrical connectors  722  configured to convey an electrical output from second set of quantum dots  712  out of solar panel  700 . Electrical connector  721  can be generally transparent to wavelengths that are absorbed by second solar cell  702  and/or wavelengths that are converted by second solar cell  702  to an electrical output, such that wavelengths (for example in sunlight, and the like) to which second solar cell  702  are sensitive, pass through electrical connector  721  to reach second solar cell  702 . Furthermore, electrical connectors  721 ,  722  can be located at other positions in solar panel  700  that convey electrical output out of solar cells  701 ,  702 , as will occur to persons of skill in the art. When substrate  720  is transparent, electrical connector  722  can be generally transparent to wavelengths that are absorbed by first solar cell  701  and/or wavelengths that are converted by first solar cell  701  to an electrical output, such that wavelengths (for example in sunlight, and the like) to which first solar cell  701  are sensitive, pass through electrical connector  722  (and second solar cell  702 ) to reach first solar cell  701 . However, in other implementations, solar panel  700  can comprise one electrical connector (e.g. at a position of either of electrical connectors  721 ,  722 , and/or another position), with electrical output from both solar cells  701 ,  702  flowing there through to the one electrical connector. 
     As compared to solar panels  100 ,  600 , solar panel  700  has a comparative areal advantage as each of solar cells  701 ,  702  occupy an area that is similar to an area of solar panel  700  rather than about half the area (as in solar panels  100 ,  600 ). 
     In some implementations, relative positions of solar cells  701 ,  702  can be reversed. For example, attention is next directed to  FIG. 8 , which depicts a solar panel  800  that is substantially similar to solar panel  700 , with like elements having like numbers, however in a “800” series rather than a “700” series. In particular, solar panel  800  comprises a substrate  820 , a first solar cell  801  and a second solar cell  802 . As also depicted in  FIG. 8 , first solar cell  801  comprises a respective set of quantum dots  811  and a respective semiconductor  813 , similar, respectively, to first set of quantum dots  111  and semiconductor  113 ; and second solar cell  802  comprises a respective set of quantum dots  812  and a respective semiconductor  815 , similar, respectively, to second set of quantum dots  112  and semiconductor  115 . 
     However, in contrast to solar panel  700 , in solar panel  800 , first solar cell  801  is located on substrate  820 , and second solar cell  802  is located on first solar cell  801  (e.g. first solar cell  801  is between substrate  820  and second solar cell  802 ). In general, second solar cell  802  is transparent to wavelengths that are absorbed by first solar cell  801  and/or wavelengths that are converted by first solar cell  801  to an electrical output, such that wavelengths (for example in sunlight, and the like) to which first solar cell  801  are sensitive, pass through second solar cell  802  to reach first solar cell  801 . Similarly, when substrate  820  is transparent, first solar cell  801  is transparent to wavelengths that are absorbed by second solar cell  802  and/or wavelengths that are converted by second solar cell  802  to an electrical output, such that wavelengths (for example in sunlight, and the like) to which second solar cell  802  are sensitive, pass through first solar cell  801  to reach second solar cell  802 . 
     Solar panel  800  further comprises electrical connectors  821 ,  822 , electrical connector  821  configured to convey an electrical output from first set of quantum dots  811  out of solar panel  800 , and electrical connector  822  configured to convey an electrical output from second set of quantum dots  812  out of solar panel  800 . Electrical connector  822  can be generally transparent to wavelengths that are absorbed by first solar cell  801  and/or wavelengths that are converted by first solar cell  801  to an electrical output, such that wavelengths (for example in sunlight, and the like) to which first solar cell  801  are sensitive, pass through electrical connector  822  to reach first solar cell  801 . When substrate  820  is transparent, electrical connector  821  can be generally transparent to wavelengths that are absorbed by second solar cell  802  and/or wavelengths that are converted by second solar cell  802  to an electrical output, such that wavelengths (for example in sunlight, and the like) to which second solar cell  802  are sensitive, pass through electrical connector  821  (and first solar cell  801 ) to reach second solar cell  802 . However, in other implementations, solar panel  800  can comprise one electrical connector (e.g. at a position of either of electrical connectors  821 ,  822 , and/or another position), with electrical output from both solar cells  801 ,  802  flowing there through to the one electrical connector. 
     Hence, provided herein are solar panels in which a first solar cell (e.g. solar cell  701  and/or solar cell  801 ) and a second solar cell (e.g. solar cell  702  and/or solar cell  802 ) are stacked on each other and on a substrate (e.g. substrate  820 ), an outer solar cell (e.g. a solar cell distal the substrate), of the first solar cell and the second solar cell, being transparent to respective wavelengths associated with an inner solar cell (e.g. a solar cell next to the substrate), of the first solar cell and the second solar cell. Furthermore, when the substrate can be transparent and the inner solar cell can transparent to respective associated wavelengths of the outer solar cell. 
     Yet further alternative implementations are within the scope of present implementations. For example, each of solar panels  100 ,  600 ,  700 ,  800  can be adapted to include lenses, including, but not limited to optical lenses and the like, and/or reflective layers, including, but not limited to, thin film coatings and/or partially reflective layers, and/or selectively reflective layers, and the like, to assist at increasing efficiency of the solar panels. For example, attention is next directed to  FIG. 9 , which depicts a solar panel  900  which is substantially similar to solar panel  100 , with like elements having like numbers however in a “900” series rather than a “100” series. In particular, solar panel  900  comprises a substrate  920 , a first solar cell  901  and a second solar cell  902 . As also depicted in  FIG. 9 , first solar cell  901  comprises a respective set of quantum dots  911  and a respective semiconductor  913 , similar, respectively, to first set of quantum dots  111  and semiconductor  113 ; and second solar cell  902  comprises a respective set of quantum dots  912  and a respective semiconductor  915 , similar, respectively, to second set of quantum dots  112  and semiconductor  115 . Solar panel  900  further comprises electrical connectors  921 ,  922  similar to electrical connectors  121 ,  122 . 
     However, in contrast to solar panel  100 , solar panel  900  further comprises one or more lenses  970  configured to convey the sunlight, and the like into first solar cell  901  and second solar cell  902 . Specifically, lenses  970  focus light into solar cells  901 ,  902 . Again, lenses  970  are depicted in cross-section and lenses  970  can comprise an array of lenses arranged on a surface of each of first solar cell  901  and second solar cell  902 . Furthermore, while six lenses  970  are depicted for each of first solar cell  901  and second solar cell  902 , a number and/or size of lenses  970  can be adapted for a size and/or area of solar panel  100 . Furthermore, lenses  970  can be configured with a focal point that results in sunlight, and the like being focussed into about a midway point between top and bottom surfaces of each of first solar cell  901  and second solar cell  902 , however other focal points are within the scope of present implementations. For example, in some implementations, one or more lenses  970  can be configured with a focal point that results in sunlight, and the like being focussed into quantum dots  911 ,  912 . In general, lenses  970  assist in collecting light from the sun, and/or light from other light sources, and conveying the light into each of first solar cell  901  and second solar cell  902 . 
     Furthermore, when substrate  920  is transparent, an opposite and/or bottom side of substrate  920  can alternatively comprises lenses similar to lenses  970 , however with respective focal points adjusted accordingly. 
     Also in contrast to solar panel  100 , solar panel  900  comprises one or more reflective layers  971 ,  972  arranged to reflect sunlight, and the like passing through one or more of first solar cell  901  and second solar cell  902  back through one or more of first solar cell  901  and second solar cell  902 . For example, as depicted, reflective layer  971  is located between solar cell  901  and electrical connector  921 , and is configured to reflect light at least in first range  201  and, alternatively, light in second range  202  (and/or light in both ranges  201 ,  202 ) back into solar cell  901 . Hence, light in one or more of ranges  201 ,  202  that was not converted to an electrical output can be reflected back into solar cell  901  for further conversion into an electrical output. Alternatively, reflective layer  971  can be integrated with electrical connector  921 . Similarly, as depicted, reflective layer  972  is located between solar cell  902  and electrical connector  922 , and is configured to reflect light at least in first range  401  and, alternatively, light in second range  402  (and/or light in both ranges  401 ,  402 ) back into solar cell  902 . Hence, light in one or more of ranges  401 ,  402  that was not converted to an electrical output can be reflected back into solar cell  902  for further conversion into an electrical output. Alternatively, reflective layer  972  can be integrated with electrical connector  922 . Reflective layers  971 ,  972  can include, but are not limited to, one or more of metal layers, mirror layers and dichroic mirror layers; when reflective layers  971 ,  972  comprise dichroic mirrors, the dichroic mirrors can be specifically adapted to reflect the respective wavelength ranges for each of solar cells  901 ,  902 . It is further appreciated that any of lenses  970  and reflective layers  971 ,  972  can be optional. 
     Solar panel  600  can be adapted to include lenses and/or reflective layers similar to solar panel  900 . Similarly, solar panels  700 ,  800  can be adapted to include lenses, at least at a top surface. When similar reflective layers are integrated with solar panels  700 ,  800 , reflective layers configured to reflect light associated with a first solar cell can be farther configured to transmit light associated with the other solar cell. For example, in solar panel  700 , a reflective layer located between solar cell  701  and solar cell  702  can be configured to reflect light associated with solar cell  701  and transmit light associated with solar cell  702 . 
     In some implementations, semiconductors described herein can be adapted to be in a shape of a lens configured to convey the sunlight, and the like into a respective solar cell. For example, attention is next directed to  FIG. 10 , which depicts a solar panel  1000  which is substantially similar to solar panel  900 , with like elements having like numbers however in a “1000” series rather than a “900” series. In particular, solar panel  1000  comprises a substrate  1020 , a first solar cell  1001  and a second solar cell  1002 . As also depicted in  FIG. 10 , first solar cell  1001  comprises a respective set of quantum dots  1011  and a respective semiconductor  1013 , similar, respectively, to first set of quantum dots  111  and semiconductor  113 ; and second solar cell  1002  comprises a respective set of quantum dots  1012  and a respective semiconductor  1015 , similar, respectively, to second set of quantum dots  112  and semiconductor  115 . Solar panel  1000  further electrical connectors  1021 ,  1022  similar to electrical connectors  921 ,  922 , as well as optional reflective layers  1071 ,  1072 , respectively similar to optional reflective layers  971 ,  972   
     However, in contrast to solar panel  900 , in solar panel  1000 , a shape of each of semiconductors  1013 ,  1015  is in a shape of one or more lenses  1070  configured to convey the sunlight, and the like into a respective solar cell. For example, a side opposite substrate  1020  of each of semiconductors  1013 ,  1015  has been shaped into one or more lenses  1070 , lenses  1070  being otherwise similar to lenses  970 . Semiconductors in any of solar panels  100 ,  600 ,  700 ,  800  can be adapted accordingly. In particular, when semiconductors of solar panels  700 ,  800  are similarly adapted, a surface of a “top” semiconductor can be shaped into one or more lenses. 
     Persons skilled in the art will appreciate that there are yet more alternative implementations and modifications possible. For example, portions of semiconductors and/or quantum dots described herein can be coated with reflective layers and/or sandwiched between reflective layers, to contain light therein, to promote further conversion of light to charge; in addition portions of semiconductors and/or quantum dots described herein can be shaped in a manner which promotes total internal reflection (“TIR”) through portions of the semiconductors to further contain light in specific wavelength ranges, to promote further conversion of light to charge. 
     For example, attention is next directed to  FIG. 11  which depicts a cross-section of a portion of a solar cell  1101 , which can be similar to either of solar cells  101 ,  102 , and the like described herein. Hence, a set of quantum dots  1112  and a semiconductor  1115 , however only one quantum dot  1112  is depicted for clarity (though it is assumed that a plurality of quantum dots  1112  is present). Furthermore, a shape of a cross-section of quantum dot  1112  is depicted as being semi-circular, though quantum dot  1112  can generally comprise mesa shape and the like. In any event, solar cell  1101  further comprises a first reflective layer  1181  and a second reflective layer  1182 , which sandwich a portion  1115   a  of semiconductor  1115  there between, and portion  1115   a  having a cross-section which is half-annulus. Hence, for example, reflective layer  1182  coats quantum dot  1112 , portion  1115   a  coats reflective layer  1182 , reflective layer  1181  coats portion  1115   a , and reflective layer  1181  is capped by semiconductor  1115 . In general, reflective layer  1181  is at least partially transparent to wavelengths in light  1190  to which semiconductor  1115  is sensitive (e.g. as described above) and is generally transparent to wavelengths to which quantum dot  1112  is sensitive. Light  1190  can comprise light from sunlight, ambient light, light from radiant sources present at night and the like. Reflective layer  1182  is generally reflective to wavelengths in light  1190  to which semiconductor  1115  is sensitive (e.g. as described above) and is generally transparent to wavelengths to which quantum dot  1112  is sensitive. Hence, for example, infrared light (or UV light), and the like, enters the optical cavity formed by reflective layers  1181 ,  1182  and is converted to red light (or blue light, though neither is depicted for clarity, but assumed to be present) by portion  1115   a , which in turn passes through reflective layer  1182  where it is converted to an electrical output by quantum dot  1112 . However, infrared light (or UV light) that is not converted to red light reflects from reflective layer  1182  back into the optical cavity formed by reflective layers  1181 ,  1182  and is either reflected again into the cavity by partially reflective layer  1181  (e.g. when reflective layer is at least partially reflective of infrared light (or UV light) and/or reflected again into the cavity when a reflection angle is greater than or equal to a total internal reflection angle. Such an optical cavity can increase the efficiency of solar cell  1101  relative to solar cells without reflective layers  1181 ,  1182  as infrared light (or UV light) is reflected through the cavity increasing an interaction path with portion  1115   a  of semiconductor  1115 . In general, each quantum dot in solar cell  1101  can be associated with an optical cavity of an associated portion of semiconductor  1115  formed by associated pairs of reflective layers similar to reflective layers  1181 ,  1182 . 
     Turning now to  FIG. 12 , a cross-section of a portion of a solar cell  1201  is depicted, which solar cell  1201  can be similar to either of solar cells  101 ,  102 ,  1101  and the like described herein. Hence, solar cell  1201  can comprise a set of quantum dots  1212  and a semiconductor  1215 . While only one quantum dot  1212  is depicted for clarity, it is contemplated that a plurality of quantum dots  1212  can be present. Furthermore, a shape of a cross-section of quantum dot  1212  is depicted as being about semi-oval, though quantum dot  1212  can generally have any suitable shape including, but not limited to, mesa shape, a curved shape, a convex shape, a semi-circular shape, and the like. 
     Moreover, solar cell  1201  can further comprise a reflective layer  1281  and a reflective layer  1282 , which sandwich or enclose a portion  1215   a  of semiconductor  1215  therebetween.  FIG. 12  shows in cross-section reflective layers  1281  and  1282  meeting one another at points  1283  and  1284 . In  FIG. 12 , points  1283  and  1284  are on a surface  1285 , form which surface  1285  quantum dot  1212  extends. In other words, in  FIG. 12  quantum dot  1212  extends from surface  1285 , and reflective layers  1281  and  1282  meet one another at surface  1285 . Boundaries of semiconductor  1215  are depicted in dashed lines to indicate that in some implementations, solar cell  1201  need not comprise the portion of semiconductor  1215  outside of reflective layer  1281 . 
       FIG. 12 , similar to the other drawings described herein, is a schematic drawing intended for illustrative purposes. The actual and/or relative dimensions of the features of solar cell  1201  can vary from those shown in  FIG. 12 . 
     In some implementations, surface  1285  can comprise the surface of a substrate on which quantum dots  1212  are formed, or the surface of a coating or a layer on the surface of the substrate on which quantum dots  1212  are supported. In other implementations, quantum dots  1212  and solar cell  1201  can be self-supporting and/or free-standing, in which case there need not be a substrate to support quantum dots  1212  or solar cell  1201 . In such self-supporting or free-standing implementations, surface  1285  can comprise an outer surface of quantum dots  1212  or solar cell  1201 . In some implementations, the electric output generated by quantum dots  1212  can be collected through surface  1285 . 
     While  FIG. 12  shows reflective layers  1281  and  1282  meeting one another at points  1283  and  1284  on surface  1285 , it is contemplated that in other implementations, not shown, reflective layers  1281  and  1282  can meet one another at one or more points, and/or along lines, which can be partially or completely away or spaced from surface  1285 . 
     Reflective layers  1281  and  1282  meeting can comprise the two layers at least partially touching one another, abutting one another, intersecting one another, or otherwise at least partially coming into contact with one another such that they form an enclosure between reflective layers  1281  and  1282  within which enclosure portion  1215   a  of semiconductor  1215  can be enclosed. This enclosure can also be referred to as an optical cavity. In some implementations, not shown, the enclosure may have openings and/or a portion of its outer boundary that is not covered by reflective layers  1281  and  1282 . In the implementation shown in  FIG. 12 , the enclosure formed between reflective layers  1281  and  1282  has no opening and completely encloses portion  1215   a.    
     As shown in  FIG. 12 , portion  1215   a  can have a cross-section which is crescent-shaped or substantially crescent-shaped. In other implementations, not shown, portion  1215   a  can have a shape other than a crescent shape. 
     Moreover, in some implementations reflective layer  1282  can coat quantum dot  1212 , portion  1215   a  can coat reflective layer  1282 , reflective layer  1281  can coat portion  1215   a , and reflective layer  1281  can be capped by semiconductor  1215 . Layer  1282  coating quantum dot  1212  can comprise layer  1282  coating quantum dot  1212  directly, and/or layer  1282  coating quantum dot  1212  indirectly whereby other materials and/or layers can be disposed, at least partially, between quantum dots  1212  and layer  1282 . Similarly, portion  1215   a  coating reflective layer  1282 , reflective layer  1281  coating portion  1215   a , and/or reflective layer  1281  being capped by semiconductor  1215  can be direct or indirect, similar to the manner described in relation to quantum dots  1212  and layer  1282 . 
     Reflective layer  1281  can be at least partially transparent to wavelengths in light  1290  to which semiconductor  1215  is sensitive (e.g. as described above) and can be generally transparent to wavelengths to which quantum dot  1212  is sensitive. Light  1290  can comprise light from sunlight, ambient light, light from radiant sources present at night and the like. Reflective layer  1282  can be generally reflective to wavelengths in light  1290  to which semiconductor  1215  is sensitive (e.g. as described above) and can be generally transparent to wavelengths to which quantum dot  1212  is sensitive. 
     Hence, for example, infrared light (or UV light), and the like, can enter the optical cavity formed by reflective layers  1281 ,  1282  and can be converted to red light (or blue light, though neither is depicted for clarity, but assumed to be present) by portion  1215   a , which red light in turn passes through reflective layer  1282  where it is converted to an electrical output by quantum dot  1212 . However, infrared light (or UV light) that is not converted to red light can be reflected from reflective layer  1282  back into the optical cavity formed by reflective layers  1281 ,  1282  and can be either reflected again into the cavity by partially reflective layer  1281  (e.g. when reflective layer is at least partially reflective of infrared light (or UV light) and/or reflected again into the cavity when a reflection angle is greater than or equal to a total internal reflection angle. 
     Such an optical cavity can increase the efficiency of solar cell  1201  relative to solar cells without reflective layers  1281 ,  1282  as infrared light (or UV light) is reflected through the cavity increasing an interaction path with portion  1215   a  of semiconductor  1215 . Reflective layers  1281 ,  1282  meeting one another to enclose portion  1215   a  can further reduce the light lost from the optical cavity be reducing or eliminating portions of the outer boundary of the optical cavity which are not covered by one of reflective layers  1281 ,  1282 . 
     Moreover, in some implementations, a maximum height  1286  of reflective layer  1282  measured from surface  1285  can be about two-thirds a corresponding maximum height  1287  of reflective layer  1281  measured from the surface  1285 . 
     In addition, in some implementations, each quantum dot in solar cell  1201  can be associated with an optical cavity of an associated portion of semiconductor  1215  formed by associated pairs of reflective layers similar to reflective layers  1281 ,  1282 . 
     In any event, described herein are solar panels that include solar cells that convert light just outside the edges of the human visible spectrum into light just inside the human visible spectrum, which is turn converted into respective electrical outputs, using quantum dots in semiconductors. The ranges of light that are converted to electrical outputs are also in a range used by leaves in photosynthesis, and hence the solar panels described herein can also be referred to as biomimicry devices. Furthermore, such solar panels described herein can be adapted for use in space and/or high-altitude applications, for example, where infrared and/or ultraviolet intensities in ambient radiation can be higher than on the earth&#39;s surface, as well as polar applications, underground applications and the like. 
     Persons skilled in the art will appreciate that there are yet more alternative implementations and modifications possible, and that the above examples are only illustrations of one or more implementations. The scope, therefore, is only to be limited by the claims appended hereto.