Laminated hybrid solar cell

Abstract

The invention relates to a laminated hybrid solar cell. A stacked photovoltaic PV device includes: a substrate; a reflector layer on one side of the substrate; a first PV sub-cell in optical communication with the reflector layer configured to absorb visible light; and a second PV sub-cell on the first PV sub-cell configured to absorb NIR light.

Description

[0001] Cross-citation of related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 559,488, filed on February 29, 2024, which is incorporated herein by reference in its entirety. Technical Field

[0003] This application generally relates to tandem hybrid solar cells. Background Technology

[0004] Optoelectronic devices utilizing organic materials are becoming increasingly popular for a variety of reasons. Many materials used to manufacture such devices are relatively inexpensive, thus organic optoelectronic devices have the potential to offer a cost advantage over inorganic devices. Furthermore, the inherent properties of organic materials, such as their flexibility, make them more suitable for specific applications, such as fabrication on flexible substrates. Examples of organic optoelectronic devices include organic light-emitting devices (OLEDs), organic phototransistors, organic photovoltaic cells, and organic photodetectors. For OLEDs, organic materials can offer performance advantages over conventional materials. For example, the wavelength of light emitted by an organic emitting layer can often be easily tuned with appropriate dopants.

[0005] Photoelectric devices convert electromagnetic radiation into electricity. Solar cells, also known as photovoltaic (PV) devices or cells, are a type of photoelectric device specifically designed to generate electricity. PV devices, which can generate electricity from light sources other than sunlight, can be used to drive electrical loads to provide power for applications such as lighting, heating, or powering electronic circuit systems or devices such as calculators, radios, computers, or remote monitoring or communication equipment. These power generation applications may involve charging battery packs or other energy storage devices, allowing operation to continue when direct illumination from the sun or other light sources is unavailable, or balancing the power output of the PV device according to specific application requirements.

[0006] Traditionally, photosensitive optoelectronic devices have been composed of multiple inorganic semiconductors, such as crystalline silicon, polycrystalline silicon, amorphous silicon, gallium arsenide, cadmium telluride, etc.

[0007] Recent efforts have focused on achieving acceptable photovoltaic conversion efficiencies at economical production costs using organic photovoltaic (OPV) cells. OPV offers a low-cost, lightweight, and mechanically flexible pathway to solar energy conversion. Compared to polymers, small-molecule OPVs also have the advantage of using materials with well-defined molecular structures and weights. This results in a reliable purification pathway and the ability to deposit multiple layers using highly controlled thermal deposition without concern for dissolution and thus damage to previously deposited layers or sub-cells. Using tandem solar cells can produce even more efficient devices because each part of the tandem device can be designed to absorb light of different wavelengths, thus capturing more incident light or, if used outdoors, a wider portion of the solar spectrum. Summary of the Invention

[0008] Some embodiments of the invention disclosed herein are set forth below, and any combination of these embodiments (or portions thereof) may be made to define another embodiment.

[0009] In one aspect, a tandem photovoltaic (PV) device includes: a substrate; a reflector layer on the substrate; a first PV sub-cell optically connected to the reflector layer and configured to absorb visible light; and a second PV sub-cell located on the first PV sub-cell and configured to absorb NIR light.

[0010] In one embodiment, the first PV sub-cell comprises a perovskite sub-cell.

[0011] In one embodiment, the first PV sub-cell includes a CdTe sub-cell.

[0012] In one embodiment, the first PV sub-cell includes a Si sub-cell, a CdSeTe sub-cell, or a CIGS sub-cell.

[0013] In one embodiment, the second PV sub-cell comprises an organic sub-cell.

[0014] In one embodiment, the device further includes a charge generation layer (CGL) located between the first PV sub-cell and the second PV sub-cell.

[0015] In one embodiment, CGL comprises Ag nanoparticles.

[0016] In one embodiment, the device has a power conversion efficiency (PCE) greater than 30% or greater than 35%.

[0017] In one embodiment, the apparatus includes a membrane deposited by vacuum thermal evaporation (VTE).

[0018] In one embodiment, the device includes a solution-treated membrane.

[0019] In one embodiment, the first PV sub-cell comprises two or more PV sub-cells.

[0020] In one embodiment, the second PV sub-cell comprises two or more PV sub-cells.

[0021] In one embodiment, the second PV sub-cell is transparent or translucent in the visible spectrum.

[0022] In one embodiment, the device includes a two-terminal (2T), a three-terminal (3T), or a four-terminal (4T) device.

[0023] In one embodiment, the device is flexible.

[0024] In one embodiment, the reflector layer is configured to reflect NIR light or visible light.

[0025] In another aspect, a product includes the device described above, wherein the product is selected from the group consisting of: displays, discrete light sources, lighting panels, flat panel displays, curved displays, computer monitors, medical monitors, televisions, billboards, lights for internal or external lighting and / or signaling, head-up displays, fully transparent or partially transparent displays, flexible displays, rollable displays, foldable displays, stretchable displays, laser printers, telephones, cellular phones, tablet computers, phablets, personal digital assistants (PDAs), wearable devices, laptop computers, digital cameras, camcorders, viewfinders, microdisplays with a diagonal of less than 2 inches, 3D displays, virtual reality or augmented reality displays, vehicles, video walls comprising multiple tiled displays, theater or stadium screens, signs, electronic component modules, lighting panels, solar cells, lightweight solar cells, flexible solar cells, solar cells integrated with thin-film electronics, thin-film power supplies, solar farms, sensors, radio receivers / transmitters, audio generating devices, computing devices, IT devices, shelf labels, windows, walls, and roofs. Attached Figure Description

[0026] The foregoing objects and features, as well as other objects and features, will become apparent from the following specification and accompanying drawings, which are included to provide an understanding of the invention and form part of this specification, wherein similar numbers denote similar elements, and wherein:

[0027] Figure 1 An organic light-emitting device is shown.

[0028] Figure 2 An inverted organic light-emitting device without an independent electron transport layer is demonstrated.

[0029] Figure 3A schematic diagram illustrating a preferred embodiment of a tandem OPV-perovskite (or CdTe) tandem solar cell, which achieves efficient spectral separation and the ability to fabricate an OPV device that absorbs NIR after the perovskite sub-cell and transmit visible light through the back cell.

[0030] Figure 4 Showing detailed simulations of an organic front-side battery.

[0031] Figure 5 Showing details of a simulation of an inorganic back-side battery.

[0032] Figure 6 Showcase example device designs.

[0033] Figure 7 Showcase example device designs.

[0034] Figure 8 Showing details of the simulation of the hybrid PV device. Detailed Implementation

[0035] It should be understood that the drawings and descriptions of this invention have been simplified to illustrate elements relevant to a clear understanding of the invention, while many other elements found in related systems and methods have been omitted for clarity. Those skilled in the art will recognize that additional elements and / or steps are expected and / or required in practicing this invention. However, because such elements and steps are well known in the art, and because they are not conducive to a better understanding of the invention, a discussion of such elements and steps is not provided herein. This disclosure herein relates to all such variations and modifications of such elements and methods known to those skilled in the art.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. While any methods and materials similar to or equivalent to those described herein may be used in the practice or testing of this invention, exemplary methods and materials are described.

[0037] As used in this article, each of the following terms has its associated meaning in this section.

[0038] This article uses the articles “a” and “an” to refer to one or more (i.e., at least one) grammatical object of the article. For example, “element” means one element or more elements.

[0039] When referring to measurable values ​​such as quantity or duration, the word “about” as used herein is intended to cover deviations of ±20%, ±10%, ±5%, ±1%, or ±0.1% relative to a particular value, provided such deviations are appropriate.

[0040] Throughout this disclosure, various aspects of the invention may be presented in a range format. It should be understood that the use of a range format is for convenience and brevity only and should not be construed as a rigid limitation on the scope of the invention. Therefore, the description of a range should be considered as having precisely disclosed all possible subranges and individual numerical values ​​within those ranges. For example, a description of a range from 1 to 6 should be considered as having particularly disclosed subranges, such as 1 to 3, 1 to 4, 1 to 5, 2 to 4, 2 to 6, 3 to 6, etc., and individual numbers within those ranges, such as 1, 2, 2.7, 3, 4, 5, 5.3, 6, and any complete and partial increments therein. This applies regardless of the breadth of the range.

[0041] As used herein, the terms "electrode" and "contact" can refer to a layer that provides a medium for delivering photogenerated current to an external circuit or for providing bias current or voltage to the device. That is, an electrode or contact provides an interface between the active region of an organic photosensitive optoelectronic device and wires, leads, traces, or other components for transferring charge carriers to or from an external circuit. Examples of electrodes include anodes and cathodes, which can be used in photosensitive optoelectronic devices.

[0042] As used herein, the term "transparent" may refer to an electrode that allows at least 50% of incident electromagnetic radiation of the relevant wavelength to be transmitted through it. In photosensitive optoelectronic devices, it may be necessary to allow the maximum amount of ambient electromagnetic radiation from outside the device to enter the active internal region of the photoconductor. That is, the electromagnetic radiation must reach the photoconductor layer, where it can be converted into electricity through absorption. This typically indicates that at least one of the electrical contacts should absorb and reflect incident electromagnetic radiation to a minimum. In some cases, such contacts should be transparent or at least translucent.

[0043] As used herein, the term "semi-transparent" may refer to an electrode that allows some, but less than 50%, of ambient electromagnetic radiation of relevant wavelengths to be transmitted. The opposing electrode may be a reflective material, so that light that passes through the cell but is not absorbed is reflected back to the cell.

[0044] As used and described herein, a “layer” refers to a component or assembly of a photosensitive device whose primary dimensions are XY (i.e., along its length and width). It should be understood that the term “layer” is not necessarily limited to a single layer or sheet of material. Furthermore, it should be understood that the surfaces of certain layers, including interfaces between such layers and other materials or layers, may be imperfect, where said surfaces represent interpenetrating, entangled, or coiled networks with other materials or layers. Similarly, it should be understood that layers can be discontinuous, such that the continuity of said layer along the XY dimension may be disturbed or otherwise interrupted by other layers or materials.

[0045] As used herein, a "photosensitive region" refers to a region of the device that absorbs electromagnetic radiation to generate excitons. Similarly, if a layer absorbs electromagnetic radiation to generate excitons, it is "photosensitive." Excitons can dissociate into electrons and holes to generate an electric current.

[0046] As used herein, the terms “donor” and “acceptor” refer to the relative positions of the highest occupied molecular orbital (“HOMO”) and lowest unoccupied molecular orbital (“LUMO”) energy levels of two contacting but distinct organic materials. If one material in contact with the other has a lower LUMO energy level, then that material is the acceptor. Otherwise, it is the donor. In the absence of external bias, it is energy-advantageous to move electrons from the donor-acceptor junction into the acceptor material and to move holes into the donor material.

[0047] As used herein, if the first energy level is closer to the vacuum level, then the first "highest occupied molecular orbital" (HOMO) or "lowest unoccupied molecular orbital" (LUMO) level is "greater than" or "higher than" the second HOMO or LUMO level. Since the ionization potential (IP) is measured as a negative energy relative to the vacuum level, a higher HOMO level corresponds to an IP with a smaller absolute value (less negative IP). Similarly, a higher LUMO level corresponds to an electron affinity (EA) with a smaller absolute value (less negative EA). On a conventional energy level diagram with the vacuum level at the top, the LUMO levels of a material are higher than the HOMO levels of the same material. "Higher" HOMO or LUMO levels appear to be closer to the top of this diagram than "lower" HOMO or LUMO levels.

[0048] As used herein, the term "band gap" (E) for polymers... g The band gap can refer to the energy difference between the HOMO and LUMO. Band gaps are typically reported in electron volts (eV). Band gaps can be measured using UV-Vis spectroscopy or cyclic voltammetry. "Low band gap" polymers can refer to polymers with a band gap below 2 eV; for example, polymers that absorb light with wavelengths greater than 620 nm.

[0049] As used in this article, the term "excited binding energy" (E)B It can refer to the following formula: E B =(M + +M - )-(M*+M), where M + and M - , respectively, represent the total energy of positively and negatively charged molecules; M* and M are the molecular energies of the first singlet state (S1) and the ground state, respectively. The excitation binding energy of the acceptor or donor molecule affects the energy shift required for efficient exciton dissociation. In some instances, the hole escape rate increases with increasing HOMO shift. The exciton binding energy E of the acceptor molecule... B A decrease in this level leads to an increase in the hole escape rate of the same HOMO shift between donor and acceptor molecules.

[0050] As used in this article, power conversion efficiency (η) ρ This can be expressed as:

[0051]

[0052] Where V OC Where is the open-circuit voltage, FF is the fill factor, and J is the open-circuit voltage. SC It is the short-circuit current, and P O This refers to the input optical power.

[0053] As used herein, the term "organic" encompasses both polymeric materials and small-molecule organic materials that can be used to manufacture organic optoelectronic devices. "Small molecule" refers to any organic material that is not a polymer, and "small molecule" can actually be quite large. In some cases, small molecules may contain repeating units. For example, using long-chain alkyl groups as substituents does not remove a molecule from the "small molecule" category. Small molecules can also be incorporated into polymers, for example, as side groups on the polymer backbone or as part of the backbone. Small molecules can also act as the core portion of dendritic polymers, which comprise a series of chemical shells built upon the core portion. Dendritic polymers can be "small molecules," and it is believed that all dendritic polymers currently used in the field of organic optoelectronic devices are small molecules.

[0054] As used herein, "top" means furthest from the substrate, and "bottom" means closest to the substrate. When the first layer is described as being "placed" "above" the second layer, the first layer is placed further away from the substrate. Unless it is specified that the first layer "contacts" the second layer, other layers may exist between the first and second layers. For example, even if various organic layers exist between the cathode and anode, the cathode may still be described as being "placed" "above" the anode.

[0055] As used herein, “solution-handleable” means capable of dissolving, dispersing or transporting in and / or depositing from a liquid medium in the form of a solution or suspension.

[0056] When a ligand is believed to directly contribute to the photosensitivity of a material, the ligand can be called "photosensitive". When a ligand is believed not to contribute to the photosensitivity of a material, the ligand can be called "auxiliary", but auxiliary ligands can alter the properties of photosensitivity ligands.

[0057] As used herein, and as those skilled in the art will generally understand, on a conventional energy level diagram, where the vacuum level is at the top, "shallow" energy levels appear as higher or closer to the top, compared to "deeper" energy levels which appear as lower or closer to the bottom.

[0058] As used herein, and as will generally be understood by those skilled in the art, if the first work function has a higher absolute value, then the first work function is “greater” or “higher” than the second work function. This is because the work function is typically measured as a negative number relative to the vacuum level, meaning that the “higher” work function is more negative. On a conventional energy level diagram with the vacuum level at the top, the “higher” work function is illustrated as being farther from the vacuum level in the downward direction. Therefore, the definitions of HOMO and LUMO levels follow different rules than those for the work function.

[0059] Unless otherwise specified, any of the layers in the various embodiments may be deposited by any suitable method. For organic layers, preferred methods include thermal evaporation, inkjet printing (as described in U.S. Patent Nos. 6,013,982 and 6,087,196, which are incorporated herein by reference in their entirety), organic vapor deposition (OVPD) (as described in U.S. Patent No. 6,337,102 to Forrest et al., which are incorporated herein by reference in their entirety), and deposition via organic vapor jet printing (OVJP) (as described in U.S. Patent No. 7,431,968, which is incorporated herein by reference in its entirety). Other suitable deposition methods include spin coating and other solution-based processes. Solution-based processes are preferably performed in a nitrogen or inert atmosphere. For other layers, preferred methods include thermal evaporation. Preferred patterning methods include patterning via mask deposition, cold soldering (as described in U.S. Patents 6,294,398 and 6,468,819, which are incorporated herein by reference in their entirety), and some of the methods associated with deposition methods such as inkjet and OVJD. Other methods may also be used. The material to be deposited may be modified to suit a particular deposition method. For example, branched or unbranched substituents, preferably containing at least three carbons, such as alkyl and aryl groups, may be used in small molecules to enhance their solution handling ability. Substituents having 20 or more carbons may be used, with 3 to 20 carbons being a preferred range. Materials with asymmetric structures may have better solution handleability than materials with symmetric structures because asymmetric materials may have a lower tendency to recrystallize. Dendritic polymer substituents may be used to enhance the solution handling ability of small molecules.

[0060] The device manufactured according to embodiments of this disclosure may optionally further include a barrier layer. One use of the barrier layer is to protect the electrodes and organic layers from damage caused by exposure to harmful substances in an environment containing moisture, vapor, and / or gases. The barrier layer may be deposited above, below, or adjacent to a substrate or electrode, or above any other part of the device (including edges). The barrier layer may comprise a single layer or multiple layers. The barrier layer can be formed using a variety of known chemical vapor deposition techniques and may comprise compositions having a single phase as well as compositions having multiple phases. Any suitable material or combination of materials may be used for the barrier layer. The barrier layer may incorporate inorganic or organic compounds, or both. Preferred barrier layers comprise mixtures of polymeric and non-polymeric materials, as described in U.S. Patent No. 7,968,146, PCT Patent Application Nos. PCT / US2007 / 023098 and PCT / US2009 / 042829, which are incorporated herein by reference in their entirety. For the process to be considered a "mixture," the aforementioned polymeric and non-polymeric materials constituting the barrier layer should be deposited and / or deposited simultaneously under the same reaction conditions. The weight ratio of polymeric to non-polymeric materials can range from 95:5 to 5:95. The polymeric and non-polymeric materials can be produced from the same precursor materials. In one example, the mixture of polymeric and non-polymeric materials is essentially composed of polymeric silicon and inorganic silicon.

[0061] While certain embodiments of this disclosure are discussed with respect to a particular device or device type (e.g., OPV), it should be understood that the disclosed improvements are equally applicable to other devices, including but not limited to OLEDs, PLEDs, charge-coupled devices (CCDs), light sensors, etc.

[0062] While the exemplary embodiments described herein may be presented as methods for producing specific circuits or devices (e.g., OPVs), it should be understood that the materials and structures described herein can also be used in devices other than OPVs. For example, other optoelectronic devices such as OLEDs and organic photodetectors can employ the materials and structures described. More generally, organic devices, such as organic transistors, or other organic electronic circuits or components, can use the materials and structures described.

[0063] In some embodiments, the optoelectronic device has one or more properties selected from the group consisting of: flexibility, rollability, foldability, stretchability, and bendability. In some embodiments, the optoelectronic device is transparent or translucent. In some embodiments, the optoelectronic device further includes a layer comprising carbon nanotubes.

[0064] Devices manufactured according to embodiments of the present invention can be incorporated into a wide variety of electronic component modules (or units), which can be incorporated into a variety of electronic products or intermediate components. Examples of such electronic products or intermediate components include displays, lighting devices (e.g., discrete light source devices or lighting panels), etc., which can be utilized by end-user product manufacturers. The electronic component module may optionally include driving electronics and / or a power supply. Devices manufactured according to embodiments of the present invention can be incorporated into a wide variety of consumer products, wherein one or more electronic component modules (or units) are incorporated therein. A consumer product comprising an OPV, wherein the organic layer of the OPV contains compounds of the present disclosure. The consumer product should include any type of product comprising one or more light sources and / or one or more of some type of visual display. Examples of the consumer products described include flat panel displays, curved displays, computer monitors, medical monitors, televisions, billboards, lights for internal or external lighting and / or signaling, head-up displays, fully transparent or partially transparent displays, flexible displays, rollable displays, foldable displays, stretchable displays, laser printers, telephones, cellular phones, tablet computers, phablets, personal digital assistants (PDAs), wearable devices, laptop computers, digital cameras, camcorders, viewfinders, microdisplays with a diagonal of less than 2 inches, 3D displays, virtual reality or augmented reality displays, vehicles, video walls comprising multiple tiled displays, theater or stadium screens, and signage. Various control mechanisms, including passive and active matrices, can be used to control the devices manufactured according to the invention. Many of the devices are intended for use in temperature ranges comfortable for humans, such as 18°C ​​to 30°C, and more preferably at room temperature (20-25°C), but can be used outside this temperature range (e.g., -40°C to 80°C).

[0065] According to embodiments, devices manufactured according to embodiments of the present invention can be incorporated into one or more devices selected from consumer products, electronic component modules, lighting panels, and / or signs or displays. Further examples of such electronic products or intermediate components include solar cells, lightweight solar cells, flexible solar cells, solar cells integrated with thin-film electronics for power conversion and management, thin-film power supplies consisting of OPV cells integrated with thin-film electronics for power consumption and management, solar farms containing one or more OPV cells and / or devices that can be integrated into an array, solar farms containing translucent OPV cells and / or devices with advantages related to plants / crops, OPV devices having integrated or external electronics on the same substrate as displays such as thin-film displays, OPVs integrated with one or more sensors including, but not limited to, mechanical, electrical, and / or biosensors, OPVs on the same substrate as radio receivers / transmitters, OPVs on the same substrate as audio generating devices, OPVs on the same substrate as computing devices, OPVs for powering IT devices, OPVs for powering shelf labels, OPVs for indoor applications, OPVs for integration with windows, walls, roofs, etc., and OPVs for solar energy applications. In embodiments, the OPV device may be fully or partially transparent, flexible, bendable, rollable, foldable, or stretchable.

[0066] According to embodiments, the device manufactured according to embodiments of the present invention can be combined with a battery located on the same substrate as the device, or connected to a battery located on a different substrate / device. According to embodiments, the battery can be a standard battery and / or a thin-film battery.

[0067] According to an embodiment, the manufactured device may be a thin-film OPV device. In an embodiment, a thin-film device is one in which the layers of the device are deposited rather than placed on a substrate.

[0068] Figure 1 Examples of the layers of a single-junction solar cell or organic photovoltaic (OPV) cell 100 are depicted. An exemplary OPV 100 includes an anode 102, a cathode 104, an active layer 106, an intermediate layer 108, and another intermediate layer 110.

[0069] An OPV cell may include two electrodes having an anode 102 and a cathode 104 stacked on top of each other, at least one donor composition, and at least one acceptor composition, wherein the donor-acceptor material or active layer 106 is located between the two electrodes 102 and 104. In some embodiments, the active layer 106 may be an organic heterojunction, as described below. In some embodiments, at least one intermediate layer 108 may be located between the anode 102 and the active layer 106. Alternatively or additionally, at least one intermediate layer 110 may be located between the active layer 106 and the cathode 104.

[0070] Still referencing Figure 1 The anode 102 may comprise a conductive oxide, a thin metal layer, or a conductive polymer. In some examples, the anode 102 comprises (e.g., a transparent) conductive metal oxide, such as indium tin oxide (ITO), tin oxide (TO), gallium indium tin oxide (GITO), zinc oxide (ZO), or zinc indium tin oxide (ZITO). In other examples, the anode 102 comprises a thin metal layer, wherein the metal is selected from the group consisting of Ag, Au, Pd, Pt, Ti, V, Zn, Sn, Al, Co, Ni, Cu, Cr, or combinations thereof. In still other examples, the anode 102 comprises (e.g., a transparent) conductive polymer, such as polyaniline (PANI) or 3,4-polyvinylenedioxythiophene:polystyrene sulfonate (PEDOT:PSS). The thickness of the anode 102 may be 0.1-100 nm, 1-10 nm, 0.1-10 nm, or 10-100 nm.

[0071] Continue to refer to Figure 1 The cathode 104 may be a conductive oxide, a thin metal layer, or a conductive polymer, similar to or different from the materials discussed above for the anode 102. In some instances, the cathode 104 may comprise a metal or a metal alloy. The cathode 104 may comprise Ca, Al, Mg, Ti, W, Ag, Au, or another suitable metal or an alloy thereof. The thickness of the cathode 104 may be 0.1-100 nm, 1-10 nm, 0.1-10 nm, or 10-100 nm.

[0072] In some embodiments, the optoelectronic device further includes a flexible plastic substrate as one of its layers. As used herein, a flexible plastic substrate is defined as the bottom component of a solar cell. The substrate can protect the back side of the optoelectronic device from weather conditions and can mitigate any risk of electric shock, such as varying environmental conditions like moisture, UV exposure, and other performance threats. The substrate may further include multilayer adhesives, barrier films, and / or polymers. The flexible plastic substrate can have any of the properties of any substrate previously described herein. In some embodiments, the flexible plastic substrate can be positioned under the active layer 106 or an organic heterojunction. In some embodiments, the flexible plastic substrate comprises plastic, glass, or other suitable materials, such as materials that are transparent to at least a portion of the emission spectrum of the OPV. The thickness of the flexible plastic substrate can be in the range of 10-100 μm.

[0073] In some embodiments, the optoelectronic device further includes a coating or barrier layer located above a flexible plastic substrate. Anode 102 and cathode 104 are positioned above the coating. One use of the coating above the flexible plastic substrate is to protect the electrodes and organic layers of the OPV from damage caused by exposure to harmful substances in an environment containing moisture, vapor, and / or gases. The coating may be deposited above, below, or adjacent to the substrate and electrodes, or above any other part of the device (including edges). The coating may comprise a single layer or multiple layers. The coating can be formed using a variety of known chemical vapor deposition techniques and may comprise compositions having a single phase as well as compositions having multiple phases. Any suitable material or combination of materials may be used for the coating. The coating may comprise glass or a polymer. The coating may incorporate inorganic or organic compounds, or both. Exemplary coatings comprise mixtures of polymeric and nonpolymeric materials, as described in U.S. Patent Nos. 7,968,146, PCT Patent Applications Nos. PCT / US2007 / 023098 and PCT / US2009 / 042829, which are incorporated herein by reference in their entirety. For the purposes of being considered a “mixture,” the aforementioned polymeric and nonpolymeric materials constituting the barrier layer should be deposited and / or deposited simultaneously under the same reaction conditions. The weight ratio of the polymeric to nonpolymeric material can range from 95:5 to 5:95. The polymeric and nonpolymeric materials can be produced from the same precursor material. In one example, the mixture of polymeric and nonpolymeric materials is composed of polymeric silicon and inorganic silicon.

[0074] As mentioned above, in some embodiments, the OPV may include one or more intermediate layers, such as charge collection and transport intermediate layers, positioned between the anode 102, the cathode 104, and the active region or layer 106. Intermediate layers 108 and 110 may be metal oxides. In some instances, intermediate layers 108 and 110 comprise MoO3, V2O5, ZnO, or TiO2. In some instances, the first intermediate layer 108 has a composition similar to that of the second intermediate layer 110. In other instances, the first intermediate layer 108 and the second intermediate layer 110 have different compositions. The thickness of each intermediate layer may be 0.1-100 nm, 1-10 nm, 0.1-10 nm, or 10-100 nm.

[0075] In some embodiments, the active region or layer 106 located between electrodes 102, 104 comprises a composition or molecule having an acceptor and a donor. In embodiments, the optoelectronic device described herein has an organic heterojunction located within the active layer 106 between the anode 102 and the cathode 104. The organic heterojunction has a donor or donor material and an acceptor or acceptor material. In some embodiments, the composition may be arranged as an acceptor-donor-acceptor (ADA).

[0076] In some embodiments, the device includes an encapsulation layer positioned above the anode 102 and the cathode 104. The encapsulation layer may have any of the properties of the coating described above or be made of the same material as the coating described above. The encapsulation layer may comprise a single layer or multiple layers. The encapsulation layer may be formed using various known chemical vapor deposition techniques and may comprise compositions having a single phase as well as compositions having multiple phases. Any suitable material or combination of materials may be used for the encapsulation layer. The encapsulation layer may comprise glass or a polymer. The encapsulation layer may incorporate inorganic or organic compounds or both. Preferred encapsulation layers may comprise a mixture of polymeric and non-polymeric materials, as described in U.S. Patent No. 7,968,146, PCT Patent Application Nos. PCT / US2007 / 023098 and PCT / US2009 / 042829, which are incorporated herein by reference in their entirety. In one example, the mixture of polymeric and non-polymeric materials comprises polymeric silicon and / or inorganic silicon.

[0077] In some embodiments, the encapsulation layer may be the outermost layer of the flexible optoelectronic device and may be configured to help protect the inner layers (including the cathode and anode) from environmental or other external conditions. In embodiments, the encapsulation layer may surround the entire flexible optoelectronic device, or an additional protective layer may be provided on top of the encapsulation layer.

[0078] Furthermore, the encapsulation layer may comprise multiple layers, wherein the multiple layers comprise multiple molecular divisors. As used herein, the term "molecular divisor" refers to a pair of different material layers. Multiple layers comprising multiple divisors can help further enhance the protection provided by the encapsulation layer. In one embodiment, the multiple layers comprising multiple divisors may comprise glass or any other similar material. The multiple layers may comprise any material described with respect to the coatings previously described herein. The multiple layers may incorporate inorganic or organic compounds, or both. The multiple layers may comprise any number of divisors, such as 2 to 10, 3 to 8, or 4 to 6 divisors. In one embodiment, the multiple layers comprising divisors may contain three divisors. In another embodiment, the multiple layers comprising divisors may contain two divisors. In addition, each of the two halves in the multilayer composed of two halves can have a specific thickness. In some embodiments, the specific thickness can be in the range of 10-500nm, or between 10nm and 200nm, or between 10nm and 100nm, or between 10nm and 50nm, or between 20nm and 80nm, or between 40nm and 80nm.

[0079] In some embodiments, the multiple halves in the multilayer may be separated by a polymer positioned between each halves. The polymer may be any of a class of natural or synthetic substances composed of macromolecules consisting of a large number of monomers. The polymer may be any polymer as previously described herein or as described in the referenced applications or disclosures. The polymer between each halves allows a maximum amount of light to irradiate the transmitting device. Each polymer layer may have a thickness in the range of 1-10 μm.

[0080] For reference Figure 2 Examples of the individual layers of a tandem or multi-junction solar cell or organic photovoltaic (OPV) cell 200 are depicted. An OPV cell may comprise two electrodes having an anode 202 and a cathode 204 stacked in a superimposed relationship, at least one donor composition and at least one acceptor composition located within multiple active layers or regions 206A, 206B positioned between the two electrodes 202, 204. Although in Figure 2 Only two active layers or regions 206A and 206B are depicted herein, but additional active layers or regions are possible for the invention described herein. Anode 202 may also have any of the same quality or characteristics as described above for anode 102. Cathode 204 may also have any of the same quality or characteristics as described above for cathode 104. Multiple active layers or regions 206A and 206B may also have any of the same quality or characteristics as described above for active layer or region 106. At least one intermediate layer 208 may also have any of the same quality or characteristics as described above for intermediate layers 108 and 110.

[0081] In one embodiment, at least one intermediate layer 208 may be located between the anode 202 and the first active layer 206A. Alternatively, at least one intermediate layer 210 may be located between the second active layer 206B and the cathode 204. Furthermore, in another embodiment, at least one intermediate layer 212 may be located between the first active layer 206A and the second active layer 206B. The composition, thickness, etc., of each layer may be referenced. Figure 1 The same applies to those discussed.

[0082] In one embodiment, multiple active layers or regions 206A, 206B may comprise an organic heterojunction including donor and acceptor materials. In another embodiment, the organic heterojunction may be its own organic layer or part of any other organic layer, as long as it is positioned between the electrodes. The active regions or layers 106, 206A, 206B positioned between the electrodes comprise compositions or molecules having acceptors and donors. The compositions may be arranged in an acceptor-donor-acceptor (ADA) configuration.

[0083] The OPV 200 may further include an encapsulation layer comprising glass or polymer positioned above the anode and cathode. The encapsulation layer may consist of a multilayer of two-part components, as previously described. The multilayer of two-part components may be separated by a polymer layer between each two part.

[0084] The composition, thickness, etc. of each layer can be referenced. Figure 1 The same applies to those discussed.

[0085] For reference Figure 3 Tandem solar cells are an ideal way to efficiently convert the solar spectrum into electrical energy. Each sub-cell within the entire tandem device can absorb different portions of the incident light or solar spectrum, and thus increase the device's current output by absorbing more light and generating more electricity. The advantages of thin-film methods include low manufacturing cost, low processing temperature, and low embedding energy. Considering the available material systems consisting of perovskite, organic materials, and CdTe, only organic materials have good absorption rates in the near-infrared region. Therefore, a high-efficiency tandem device can be fabricated by combining two sub-cells (either an organic sub-cell with a perovskite sub-cell, or an organic sub-cell with a CdTe sub-cell). In one embodiment, the organic sub-cell can be combined with a CIGS (copper indium gallium selenide) sub-cell.

[0086] In one embodiment, a visible light-absorbing sub-cell (e.g., perovskite, CdTe, or CIGs sub-cell) may be configured to primarily absorb light in the 400 nm to 700 nm range or the 350 nm to 750 nm range. In one embodiment, a NIR (near-infrared)-absorbing sub-cell may be configured to absorb light in the 700 nm to 1000 nm range, the 700 nm to 1200 nm range, the 750 nm to 1000 nm range, or the 750 nm to 1200 nm range. In some embodiments, the NIR-absorbing sub-cell may also absorb some light within the visible spectrum, such as light in the 400 nm to 700 nm range or the 350 nm to 750 nm range.

[0087] In some embodiments, device 300 includes a substrate 301, a textured back reflector 302 above the substrate 301, one or more high-energy-absorbing cells 303, and a low-energy-absorbing cell 304 facing the incident radiation. However, processing limitations require the organic device to be the last or top sub-cell in the manufacturing process, thus meaning that the incident light will be absorbed in the red-light-absorbing cell, which is generally disadvantageous from an efficiency standpoint because red-light-absorbing cells typically have a lower open-circuit voltage than blue-light-absorbing cells; therefore, it is preferable to absorb blue light in the blue-light-absorbing cell rather than the red-light-absorbing cell. To meet all these requirements, the disclosed novel device includes a stack in which light enters a translucent OPV sub-cell 304, which absorbs low-energy (red and near-infrared) light and transmits visible light to a higher-energy perovskite, CdTe, or CIGS cell 303 placed below the transparent OPV sub-cell 304, thus closer to the back reflector 302 and farther from the incident light. Therefore, the OPV sub-cell will not absorb visible light. Generally speaking, the chemicals used to produce perovskite solar cells and the processing (annealing) temperature can damage organic solar cells.

[0088] Device 300 requires the integration of a top cell and a bottom cell. This integration can include direct electrical connections (e.g., via a 2-terminal device) or optical integration (e.g., via a 4-terminal device), where the two sub-cells may or may not be in physical contact with each other. Electrical interconnection between the cells can be provided by an Ag nanoparticle layer sandwiched between the ETL and HTL, with one cell contacting the perovskite cell 303 and the other contacting the organic cell 304, depending on whether the cell-facing interface is a cathode or anode. This charge-generating layer can use one of many different structures, as previously described in patents or publications previously incorporated herein by reference in their entirety, such as Forrest's *Organic Electronics: Foundations to Applications*, 2020, Sec. 7.5.2.

[0089] Series connection requires current matching between the sub-cells (303, 304). In this case, the current of the sub-cells (303, 304) can be matched by changing the relative thickness of their active regions. The specific thickness of the active region can be selected based on the specific materials used in each sub-cell, but suitable ranges could also be, for example, 50nm to 1000nm, or 50nm to 800nm, or 50nm to 600nm, or 50nm to 500nm, or 50nm to 400nm, or 50nm to 300nm, or 50nm to 200nm, or 50nm to 100nm, or 200nm to 1000nm, or 300nm to 1000nm, or 400nm to 1000nm, or 50nm to 1000nm, or 50nm to 1000nm. 0nm to 1000nm, or 500nm to 1200nm, or 50nm to 1200nm, or 200nm to 300nm, or 300nm to 400nm, or 400nm to 500nm, or 500nm to 600nm, or 600nm to 700nm, or 700nm to 800nm, or 800nm ​​to 900nm, or 900nm to 1000nm, or 1000nm to 1100nm, or 1100nm to 1200nm, or any other suitable range.

[0090] Alternatively, the two sub-cells (303, 304) can be grown on separate glass substrates and can be stacked. Stacking can be mechanical or performed via cold welding of the bottom contacts of the top cell 304 to the top contacts of the bottom cell 303. Either configuration (integrated or with separate substrates) allows the center contact between the sub-cells to be pulled out, enabling two-terminal (2T), three-terminal (3T), and four-terminal (4T) contact configurations, such as those included herein by reference in full in Forrest's Organic Electronics, 2020. Figure 7 As described in .14, the 3T and 4T configurations eliminate current matching constraints.

[0091] An optical reflective layer 302 can be integrated onto the back surface of the stack to reflect any unabsorbed IR light back into the cell, thereby increasing the current of the OPV cell. Current matching can also be achieved by absorbing visible radiation through a coupling filter section using OPV designed for this purpose.

[0092] The typical design of tandem solar cells places light incident on the top-absorbing cell for shorter wavelengths, while the cell that absorbs red light / NIR is positioned below, thus closer to the back reflector.

[0093] From a manufacturing perspective, for a stacked device with an OPV 304 and a perovskite (or CdTe) sub-cell 303, it is preferable to place the OPV sub-cell 304 above the perovskite (or CdTe or CIGS) sub-cell 303 to prevent damage to the OPV device during handling of the perovskite / CdTe / CIGS cells. To manufacture high-performance perovskite cells, the device is typically annealed at temperatures above 300°C. If the organic sub-cell is located below the perovskite cell during annealing, it will lead to catastrophic failure of the organic sub-cell.

[0094] Another advantage is that organic cells can absorb some UV light, which could otherwise damage perovskite cells. This is because high-energy UV light can cause bonds in the perovskite material to break, thus creating defects that act as non-radiative recombination sites, accelerating the degradation process, reducing the efficiency of the device, and weakening the stability of the solar cell.

[0095] The desired outcome is that visible light is absorbed in the perovskite (or CdTe) sub-cell 303 rather than in the OPV sub-cell 304, because the perovskite / CdTe sub-cell 303 would produce a higher voltage than the OPV sub-cell 304 for absorbed visible energy photons. Therefore, the disclosed design combines a transparent, translucent, or largely transparent OPV 304 above the perovskite (or CdTe) 303, such that NIR is absorbed in the top OPV cell 304, while visible light is absorbed in the bottom perovskite (or CdTe) cell 303. In some embodiments, the OPV 304 is at least 25% transparent to light in the visible spectrum, or at least 30%, or at least 50%, or at least 60%, or at least 70%, or at least 75%, or at least 80%, or at least 85%, or at least 90%, or at least 95%, or at least 97%, or at least 98%, or at least 99%, wherein the visible spectrum can be defined as being between 380 nm and 700 nm or between 400 nm and 700 nm.

[0096] Figure 3 A schematic diagram of an exemplary tandem PV cell 300 is shown. The OPV device 300 can be made from a film deposited by vacuum thermal evaporation (VTE), a film sputtered, and / or solution treated. The device 300 can be configured as a two-terminal, three-terminal, or four-terminal device. Unlike other devices that use crystalline Si as an NIR absorber, the device 300 can be fabricated on a flexible and lightweight substrate such as plastic.

[0097] In some embodiments, the tandem solar cell 300 comprises two or more sub-cells (303, 304), wherein one or more sub-cells are organic cells 304 and one or more sub-cells are perovskite and / or CdTe cells 303. In some embodiments, the organic cell 304 is positioned closest to the incident light (top cell) and absorbs NIR light while allowing visible light to pass through the bottom perovskite or CdTe cell 303. In some embodiments, this may be the only feasible approach to achieving a thin-film PV device with a PCE greater than 30% or even greater than 35% PCE. The film between the external electrodes can have any thickness, for example, between 300 nm and 3000 nm, or between 300 nm and 2500 nm, or between 300 nm and 2000 nm, or between 500 nm and 1000 nm, or between 300 nm and 1000 nm, or between 500 nm and 2000 nm, or between 300 nm and 1500 nm, or any other suitable thickness.

[0098] In some embodiments, the tandem solar cell 300 includes two or more sub-cells (303, 304), wherein the sub-cell 304 closest to the incident radiation (top cell) mainly absorbs NIR, and the bottom sub-cell 303 mainly absorbs visible light.

[0099] In some embodiments, the power conversion efficiency (PCE) of device 300 is greater than 10%, greater than 15%, greater than 18%, greater than 20%, greater than 25%, or greater than 30%. In some embodiments, the top cell 304 is organic. In some embodiments, the bottom cell 303 is perovskite. In some embodiments, the bottom cell 303 is CdTe, Si, CdSeTe, CIGS, or the like, or any combination thereof.

[0100] In some embodiments, the increased PCE stems from the nature of the stacked device formed using OPV and perovskite cells to absorb different portions of the solar spectrum, wherein each photon is absorbed in a cell that maximizes the voltage generated by that photon absorption, and the specific efficiency will depend on the specific chemical composition of the two types of sub-cells.

[0101] In some embodiments, a charge generation layer (CGL) is deposited between sub-cells (303, 304). In some embodiments, the CGL comprises nanoparticles, such as Ag nanoparticles. In some embodiments, other metal nanoparticles may be used alternatively or in combination.

[0102] In some embodiments, two or more sub-cells can be grown on separate substrates and then stacked together, for example, via cold soldering.

[0103] In some embodiments, the optical reflective layer 302 may be integrated onto the stacked back surface. In some embodiments, one or more optical reflective layers 302 may be textured. The reflective layer 302 may include a regular or substantially regular texture, such as a two-dimensional repeating pattern comprising one or more geometric shapes, such as a hemisphere, an oval cross section, or other semi-polyhedral shapes. In some embodiments, the reflective layer 302 may have a random texture. In some embodiments, the reflective layer may have a regular or substantially regular texture in one dimension and a random texture in orthogonal dimensions.

[0104] One or more reflective layers 302 may comprise any suitable material, such as silver (Ag), gold (Au), aluminum, tin, copper, etc. In some embodiments, the textured reflector 302 may comprise: a first reflective layer positioned in contact with the substrate 301, the first reflective layer being smooth, textured, or substantially smooth; and a second transparent layer positioned between the first reflective layer and the first solar cell 303, wherein the second transparent layer is independently smooth, textured, or substantially smooth.

[0105] Suitable reflectors have high reflectivity for both visible and NIR light, and in some embodiments may be textured to increase the path length of reflected light, thereby improving absorption. In some embodiments, the reflector has a reflectivity of at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, or at least 95% for visible and / or NIR light.

[0106] Combination with other materials

[0107] The materials described herein for use in specific layers of organic optoelectronic devices can be used in combination with a wide variety of other materials present in the device. The materials described or mentioned below are non-limiting examples of materials that can be used in combination with the compounds disclosed herein, and those skilled in the art can readily consult the literature to identify other materials that can be used in combination.

[0108] conductive dopants

[0109] Charge transport layers can be doped with conductive dopants to substantially alter their charge carrier density, which in turn changes their conductivity. Conductivity is increased by generating charge carriers in the matrix material and, depending on the type of dopant, can also achieve changes in the Fermi level of the semiconductor. Hole transport layers can be doped with p-type conductive dopants, while n-type conductive dopants are used in electron transport layers.

[0110] Experimental Examples

[0111] The invention will now be described with reference to the following examples. These examples are provided for illustrative purposes only, and the invention should in no way be construed as limited to these examples, but rather as encompassing any and all variations that become apparent from the teachings provided herein.

[0112] Without further description, it is believed that those skilled in the art can make and utilize the invention and practice the claimed methods using the foregoing description and the following illustrative examples. Therefore, the following working examples specifically point to exemplary embodiments of the invention and are not to be construed as limiting the remainder of this disclosure in any way.

[0113] Figure 4 Showing detailed simulations of an organic front-side battery. Figure 5 Showing details of a simulation of an inorganic back-side battery.

[0114] Figure 6 The example device design is shown. Early spacer layers (PEDOT:PSS) created an energy barrier for charge transport. Replacing the spacer layer with ZnO may cause UV emission. SnO2 spacer layers may cause charge imbalance. Figure 7 Showcase example device designs.

[0115] Figure 8 Showing details of the simulation of the hybrid PV device.

[0116] References

[0117] The following are each publicly disclosed and are hereby incorporated herein by reference in their entirety:

[0118] Che, X., Li, Y., Qu, Y., et al. High fabrication yield organic tandem photovoltaics combining vacuum- and solution-processed subcells with 15% efficiency. *Nature Energy*, 3, 422-427 (2018). https: / / doi.org / 10.1038 / s41560-018-0134-z

[0119] Xu, C., Ma, X., Zhao, Z., Jiang, M., Hu, Z., Gao, J., Deng, Z., Zhou, Z., An, Q., Zhang, J., and Zhang, F. (2021), Over 17.6% Efficiency Organic Photovoltaic Devices with Two Compatible Polymer Donors. Solar Power Generation (Sol.RRL) 5: 2100175. https: / / doi.org / 10.1002 / solr.202100175

[0120] Dangqi Fang and Yaqi Li, Structural, electronic, and optical properties of ZnO:ZnSnN2 compounds for optoelectronics and photocatalyst applications, *Physics Letters A*, Vol. 384, No. 26, 2020, 126670, ISSN 0375-9601. https: / / doi.org / 10.1016 / j.physleta.2020.126670 .

[0121] Dai, X.; Koshy, P.; Sorrell, CC; Lim, J.; Yun, JS; A Focused Review of Utilization of Graphene-Based Materials in Electron Transport Layer in HalidePerovskite Solar Cells: Materials-Based Issues. *Energies*, 2020, 13, 6335. https: / / doi.org / 10.3390 / en13236335

[0122] Chayanit Wechwithayakhlung, Suttipong Wannapaiboon, Sutassana Na-Phattalung, Phisut Narabadeesuphakorn, Similan Tanjindaprateep, SaranWaiprasoet, Thidarat Imyen, Satoshi Horike and Pichaya Pattanasattayavong, "Inorganic Chemistry (Inorganic Chemistry)" 2021 60(21), 16149-16159, DOI: 10.1021 / acs.inorgchem.1c01813

[0123] Shah, A., Pandey, R., Nicholson, A., Lustig, Z., Abbas, A., Danielson, A., Walls, J., Munshi, A., and Sampath, W. (2021), Understanding the Role of CdTe in Polycrystalline CdSe x Te1-x / CdTe-Graded Bilayer Photovoltaic Devices. Solar Power Generation (Sol.RRL) 5: 2100523. https: / / doi.org / 10.1002 / solr.202100523

[0124] Stephen Forrest, *Organic Electronics: Foundations to Applications*, Oxford University Press, 2020.

[0125] Every patent, patent application, and disclosure cited herein is hereby incorporated in its entirety. While the invention has been disclosed with reference to specific embodiments, it will be apparent to those skilled in the art that other embodiments and variations of the invention can be devised without departing from its true spirit and scope. The appended claims are intended to be construed as encompassing all such embodiments and equivalent variations.

Claims

1. A tandem photovoltaic (PV) device, comprising: Substrate; A reflector layer located on one side of the substrate; A first PV sub-cell, which is optically connected to the reflector layer, is configured to absorb visible light; as well as A second PV sub-cell, located on top of the first PV sub-cell, is configured to absorb NIR light.

2. The apparatus according to claim 1, wherein the first PV sub-cell comprises a perovskite sub-cell, a CdTe sub-cell, a Si sub-cell, a CdSeTe sub-cell, or a CIGS sub-cell.

3. The apparatus according to claim 1, wherein the second PV sub-cell comprises an organic sub-cell.

4. The apparatus of claim 3, wherein the second PV sub-cell is at least 30% transparent in the visible spectrum, or 50% transparent in the visible spectrum.

5. The apparatus of claim 1, further comprising a charge generation layer CGL located between the first PV sub-cell and the second PV sub-cell.

6. The apparatus of claim 4, wherein the CGL comprises Ag nanoparticles.

7. The apparatus of claim 1, wherein the apparatus has a power conversion efficiency (PCE) greater than 30% or greater than 35%.

8. The apparatus of claim 1, wherein the apparatus comprises a membrane deposited by vacuum thermal evaporation VTE.

9. The apparatus of claim 1, wherein the apparatus comprises a solution-treated membrane.

10. The apparatus of claim 1, wherein the first PV sub-cell comprises two or more PV sub-cells.

11. The apparatus of claim 1, wherein the second PV sub-cell comprises two or more PV sub-cells.

12. The device according to claim 1, wherein the device comprises a two-terminal 2T, a three-terminal 3T, or a four-terminal 4T device.

13. The apparatus of claim 1, wherein the apparatus is flexible.

14. The apparatus of claim 1, wherein the reflector layer is configured to reflect NIR light or visible light.

15. A product comprising the apparatus of claim 1, wherein the product is selected from the group consisting of: displays, discrete light sources, lighting panels, flat panel displays, curved displays, computer monitors, medical monitors, televisions, billboards, lights for internal or external lighting and / or signaling, head-up displays, fully transparent or partially transparent displays, flexible displays, rollable displays, foldable displays, stretchable displays, laser printers, telephones, cellular phones, tablet computers, tablet phones, personal digital assistants (PDAs), wearable devices, laptop computers, digital cameras, camcorders, viewfinders, microdisplays with a diagonal of less than 2 inches, 3D displays, virtual reality or augmented reality displays, vehicles, video walls comprising multiple displays tiled together, theater or stadium screens, signs, electronic component modules, lighting panels, solar cells, lightweight solar cells, flexible solar cells, solar cells integrated with thin-film electronics, thin-film power supplies, solar farms, sensors, radio receivers / transmitters, audio generating devices, computing devices, IT devices, shelf labels, windows, walls, and roofs.

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