WO2011019341A1

WO2011019341A1 - Photovoltaic devices and assembly

Info

Publication number: WO2011019341A1
Application number: PCT/US2009/053493
Authority: WO
Inventors: Stephan Clark; Scott Lerner; John Whitlock
Original assignee: Hewlett Packard Development Co LP
Current assignee: Hewlett Packard Development Co LP
Priority date: 2009-08-11
Filing date: 2009-08-11
Publication date: 2011-02-17
Anticipated expiration: 2012-02-11

Abstract

Photovoltaic devices and methods of assembly are disclosed. An exemplary method of assembling photovoltaic devices comprises providing a photovoltaic substrate on a base material in a first configuration. The method also comprises folding the base material to a second configuration. The method also comprises attaching the base material in the second configuration to a reference material to maintain the base material in the second configuration.

Description

PHOTOVOLTAIC DEVICES AND ASSEMBLY

BACKGROUND

[0001] Solar cell devices are limited by the collection efficiency of the photovoltaic cells Silicon for example has a band gap of 1.12 eV (electron volts). Photons below that energy cannot excite electrons from the valence band to the conduction band, and thus are lost as heat or by reflection. Photons with energy above 1.12 eV can be collected in silicon solar cell devices, but the energy greater than the bandgap is given up as heat. This process reduces the collection efficiency for higher energy photons.

[0002] Solar cell devices configured (o split the light into different spectral bands allows each band to collect photons with the photovoltaic cells optimized for energy collection in each band. Optical devices configured for splitting implement refractive and/or reflective elements for concentrating light, and splitting elements such as dichroics to separate the bands. Specific placement and orientation of the splitting elements require unique and complicated parts, and precise alignment in order to achieve the desired collection efficiency, making these optical devices difficult and expensive to manufacture.

[0003] Stacked solar cell devices implement upper and lower photovoltaic cells. Of course, the upper photovoltaic cells need to be transmissive to the photons which are collected by the lower cells. Absorptive losses in the top cells reduce the number of photons reaching the lower cells, thereby reducing collection efficiency of the stack In addition, transparent conductor layers are generally more resistive which reduces the collection efficiency of the stack. If opaque grid lines are used to collect electrons, the grid line shadows any photovoltaic cells positioned below (he grid line.

[0004] Multi-speclral structures split light into different wavelength "buckets"

However, this design includes a significant number of parts which need to be aligned for each optical element and photovoltaic cell, increasing complexity and cost to manufacture.

[0005] Solar collectors with optical waveguides are extensible to a large number of photovoltaic cell types. However, the complexity of making the waveguide splitting element may make manufacturing difficult, In addition, the possibility of loss from interruption of Total Internal Reflection (TlR) of the wave guide pose a significant risk with this type of design.

BRIEF DESCRIPTION OFTHE DRAWINGS

[0006] Figure 1 is a perspective view of an exemplary photovoltaic device in a first configuration.

[0007] Figure 2 is a perspective view of an exemplar)' photovoltaic device after assembly in a second configuration.

[0008] Figures 3a-k are illustrations of various exemplary configurations of photovoltaic devices which may be manufactured according to the methods described herein.

DETAILED DESCRIPTlON

[0009] Photovoltaic devices and method of assembling the photovoltaic devices are disclosed. Exemplary embodiments enable high collection efficiencies while being readily manufactured, e.g.. using a roll-ioroll sheet fabrication process. In addition, a wide variety of configurations are possible.

[0010] Exemplary embodiments of photovoltaic devices and methods of assembly may include at least one photovoltaic substrate provided on a base material in a first configuration. The first configuration may be a substantially flat or two-dimensional (2D) shape. The base material may be folded Io a second configuration. The second configuration may be a substantially three-dimensional

(3D) shape. The base material in the second configuration may be attached to a reference material to maintain the base material in the second configuration.

[0011] In an exemplary embodiment the base material may be pre-folded to a second configuration and then unfolded again into the first configuration before the photovoltaic substrate is provided on the base material.

[0012] Figure 1 is a perspective view of an exemplary photovoltaic device 100 in a first configuration 101. As mentioned above, the first configuration 101 may be a substantially flat or two-dimensional (2D) shape. The photovoltaic device 100 may be folded to a second configuration 102. Figure 2 is a perspective view of the exemplary photovoltaic device 100 after assembly in the second configuration 102,

The second configuration 102 may be a substantially three-dimensional (3D) shape

[0013] Exemplary manufacture may be accomplished as follows. A photovoltaic substrate 120 may be fabricated on or attached to a base material 110

(e.g., as a flat film) in the first configuration 101. The photovoltaic substrate 120 may comprise one or more different types of substrates, with a dichroic or slitting layer over the substrate 120. The dichroic layer (see various configurations, e g., as shown in Figures 3a-h) may be attached above the photovoltaic substrate 120b and the light hits the dichroic layer first. The dichroic layer splits the light, with some of it being transmitted to the PV under it, and some of it reflected to the other

PV. Although two types of photovoltaic substrate 120a and 120b are illustrated in

Figures 1 and 2, the embodiments described herein are not limited to any particular number or type of photovoltaic substrate 120.

[0014] Electrical interconnects, optical features (mirrors, anti-reflective coatings, photonic crystal structures), etc., may be provided on the base material

110 (e.g., by embossing) in the first configuration 101. Electrical interconnections and optical elements may also be attached to the base material HO in the first configuration 101.

[0015] The base material 110 and/or photovoltaic substrate 120 may be manufactured of one or more plastic layers, which can be much thinner than glass and thereby enables new architectures. Plastic layers may also be multifunctional, including uses as optical mechanical, electrical and thermal elements.

[0016] In an exemplary embodiment, the base material 110 may be pre-folded into the second configuration 102 prior to adding the photovoltaic substrate 120

(and/or other features), and then the base material 110 may be re-fblded into the first configuration 101 for adding the photovoltaic substrate (and/or other features).

[0017] Also in an exemplary embodiment, the base material 1 10 may be provided with features (e g , predetermined bend locations) that enhance folding or deformation of lhe base material 110. Likewise, the base material 110 may be preformed to reduce the occurrence of cracking, delaniinating. electrical opens, or optical changes due to thickness variation of the film when folding into the second configuration 102.

[0018] After attaching the photovoltaic substrate 120 to the base material 1 10, the base material 110 with photovoltaic substrate 120 may be folded into the second configuration 102. For example, the base material 110 may be pressed together in the directions of arrows 150a and 150b. The base material surrounding at least a portion of the photovoltaic substrate may be precut in order to assist with the photovoltaic substrate portion detaching in part and folding upward from the base material HO (e.g., as shown in Fig. 2), although this is not necessary. The folded base material may then be attached to a reference material 130 (e.g.. stiff plastic or glass) to maintain the base material 110 in the second configuration 102.

[0019] It is noted that assembly using arbitrary angles is more practical than other methods of construction. The "folded" designs enable definition of the photovoltaic device 100 as a substantially flat, 2D, material, and the geometry can be repeated more accurately than by building 3D structures with individual pieces or parts. By way of example, the angles of a triangle are defined by the length of its sides. That is. by folding appropriately, dimensions and angles of the triangle can be accurately and easily replicated. Curved shapes may aJso be manufactured for both reflective and refractive elements, e.g., by securing 2 points of the photovoltaic substrate 120 on the base material 1 10 and applying a compressive load between the points or by thermally forming the sheet by a forming mandrel. [0020] Other photovoltaic and/or optical devices (e.g., concentrating elements) may also be attached to the photovoltaic device 100 after assembly in the second configuration 102. Multiple photovoltaic devices 100 may also be stacked or otherwise configured together to achieve yet other designs. Exemplary designs are described below with reference to Figures 3a-k.

[0021 ] Before continuing, however, it is noted that the various designs contemplated herein provide the ability to split the light into discrete "buckets" of photons in various wavelengths. Accordingly, light may be collected more efficiently than by using single photovoltaic systems such as silicon

[0022] In addition, absorption losses from one device type to another can be reduced because resulting photovoltaic cells do not necessarily need to be transparent. The individual cells can then be optimized individually for performance for the respective portion of the solar spectra. Stacked devices can also be used to provide more complex designs.

[0023] These and other aspects may be better understood with reference the following figures and corresponding discussion below. Extensions of the shown embodiments will be readily apparent to those having ordinary skill in the art after becoming familiar with the teachings herein.

[0024] Figures 3a~k are illustrations of various configurations of photovoltaic devices 300-309 which may be manufactured, for example, as described above It is noted that whenever dots 350 are illustrated in the figures, this indicates multiple photovoltaic substrates may be present on a single photovoltaic device. [0025] In Figure 3a. lhe photovoltaic device 300 may be folded into a second configuration on base material 310 such that light is reflected in part by dichroic layer 320 on a first photovoltaic substrate 321, and transmitted in part through dichroic layer 320 on a second photovoltaic substrate 322.

[0026] In Figure 3b, the photovoltaic device 301 may be folded into a second configuration on base material 310 such that light is reflected in part by dichroic layer 320 on a first photovoltaic substrate 321, and transmitted in part through dichroic layer 320 on a second photovoltaic substrate 322.

[0027] In Figure 3c. the photovoltaic device 302 may be folded into a second configuration on base material 310 such that light is absorbed in part and transmitted in part through a third photovoltaic substrate 323. It is noted that the third photovoltaic substrate 323 may be attached on the photovoltaic device 302 after folding. The transmitted light may then be reflected in part by dichroic layer 320 on a first photovoltaic substrate 321, and transmitted in part through dichroic layer 320 on a second photovoltaic substrate 322.

[0028] In Figure 3d, the photovoltaic device 303 may be folded into a second configuration on base material 310 wherein the second configuration has a curved shape such as a corrugated cardboard structure. As such, light is absorbed in part by photovoltaic substrate 321 (and/or transmitted, e.g., to a lower lying substrate), and reflected in part by photovoltaic substrate 321 onto the photovoltaic substrate 322. and vice versa. It is noted that photovoltaic substrates 321. 322 may also absorb and/or reflect light. Other embodiments may also comprise additional photovoltaic substrates (e.g., photovoltaic substrate 323 is shown in Figure 3d) and/or one or more dichroic layers.

[0029] in Figure 3e, the photovoltaic device 304 may be folded into a second configuration on base material 310 wherein the second configuration has a curved shape such as a corrugated cardboard structure. In this embodiment, light is absorbed in part by photovoltaic substrate 321 and reflected in part by photovoltaic substrate on the photovoltaic substrate 322. In addition, at least a portion of the light may be transmitted through one or more of the photovoltaic substrates 321 and 322 onto photovoltaic substrates 324 and 325, respectively As in Figure 3d, other embodiments may also comprise additional photovoltaic substrates (e.g., photovoltaic substrate 323 is shown in Figure 3e) and/or one or more dichroic layers.

[0030] in Figure 3f, the photovoltaic device 305 may be folded into a second configuration on base materia! 310 wherein the second configuration includes layered dichroic and photovoltaic substrates and provides a louvered effect. As such, light is reflected in part and transmitted in part by dichroic layers 320, 330 on adjacent photovoltaic substrates 331, 332 and photovoltaic substrates 321 and 322.

[0031] In Figure 3g, the photovoltaic device 306 is similar in configuration to the photovoltaic device 305 shown in Figure 3f, but additional photovoltaic substrates 340a and 340b are provided. Photovoltaic substrates 340a and 340b may be mounted to the photovoltaic device 306 after folding [0032] In Figure 3b, the stacked photovoltaic device is similar in configuration to the photovoltaic device 306 shown in Figure 3g, but includes two stacked devices 306 and 306'. It is noted thai at least base material 310' may be at least partly transmissive to light. It is also noted that additional photovoltaic substrates 340a and 340b may be mounted to the photovoltaic device 307 after folding.

[0033] In Figure 3i. the photovoltaic device 307 may be folded into a second configuration on base material 310 wherein the second configuration has a curved shape such as a compound parabolic concentrator (CPC). As such, light is reflected by reflective portions 355a and 355b (e.g., mirrors) onto photovoltaic substrate 321 It is noted that the portion over the photovoltaic substrate 321 is at least partly transmissive so as not to reflect light from the photovoltaic substrate 321. Other embodiments may also comprise additional photovoltaic substrates and/or one or more dichroic layers.

[0034] In Figure 3j, lhe photovoltaic device 308 may include a dtcbroic 320 folded into a second configuration on base material 3 lOa and a reflective layer 355 (e.g., mirror) on base material 310b. As such, light is transmitted through opening 360 and reflected by dichroic 320 and reflective layer 355 onto photovoltaic substrates 321 and 322.

[003S) In Figure 3k, the photovoltaic device 309 may include a dichroic layer 320 and a photovoltaic layer 321 folded into a second configuration and mounted on base material 310 such that the dichroic layer 320 and photovoltaic layer 321 are curved or bowed. As such, light is transmitted through an at least partly iransmissive portion of the base material 310. The light is transmitted in part by dichroic 320 onto photovoltaic substrate 321, and reflected in part by dichrcύc 320 onto a reflective layer 350 (e.g., mirror). The reflected layer 350 reflects light onto the second photovoltaic substrate 322.

[0036] It is noted that the exemplary embodiments shown and described are provided for purposes of illustration and are not intended to be limiting. Still other embodiments are also contemplated.

Claims

1. A method of assembling photovoltaic devices, comprising:

providing at least one photovoltaic substrate on a base material in a first configuration;

folding the base material to a second configuration; and

attaching the base material in the second configuration to a reference material to maintain the base material in the second configuration

2. A photovoltaic device comprising.

a base material having a first configuration,

a photovoltaic substrate provided on the base material in the first configuration, the base material folded into a second configuration after the photovoltaic substrate is provided on the base material; and

a reference material provided to maintain the base material in the second configuration.

3. The method of claim I or the photovoltaic device of claim 2 further comprising the base material pre-folded to the second configuration and then unfolded again into ihe first configuration before the photovoltaic substrate is provided on the base material.

4 The method of claim 1 or the photovoltaic device of claim 2 wherein the first configuration is a substantially two-dimensional shape.

5. The method of claim 1 or the photovoltaic device of claim 2 wherein the second configuration is a substantially three-dimensional shape.

6. The method of claim I or the photovoltaic device of claim 2 wherein electrical connections are made when the base material is in the first or second configuration.

7. The method of claim 1 or the photovoltaic device of claim 2 wherein optical devices are attached when the base material is in the second configuration.

8. The method of claim 1 or the photovoltaic device of claim 2 wherein multiple photovoltaic devices are stacked on one another.

9. The method of claim 8 or the photovoltaic device of claim δ wherein each of the multiple photovoltaic devices is optimized for a portion of the solar spectrum.

10 The method of claim 8 or the photovoltaic device of claim 8 wherein each of the multiple photovoltaic devices is enhanced for a portion of the solar spectrum,.

11. The method of claim 1 or the photovoltaic device of claim 2 further comprising a plurality of photovoltaic substrates, each enhanced for a different portion of the solar spectrum.

12. The method of claim I or the photovoltaic device of claim 2 further comprising a plurality of photovoltaic substrates including both reflective substrates and refractive dielectric coatings.

13. The method of claim I or the photovoltaic device of claim 2 further comprising a plurality of photovoltaic substrates stacked on the base material.

14. The method of claim J or the photovoltaic device of claim 2 wherein the photovoltaic device includes angled shapes in the second configuration.

15. The method of claim I or the photovoltaic device of claim 2 wherein the photovoltaic device includes curved shapes in the second configuration.