Transparent conductive layer, and photovoltaic device comprising the transparent conductive layer

Abstract

Described herein are photovoltaic devices having transparent contact layers.

Description

[Technical Field]

[0001]

[0001] This specification generally relates to transparent conductive layers for photovoltaic devices, and more specifically to the use of specific combinations of materials and layer parameters to improve the efficiency of photovoltaic devices. [Background technology]

[0002]

[0002] Photovoltaic devices generate electricity by converting light into electricity using semiconductor materials that exhibit the photovoltaic effect. Certain semiconductor materials can be difficult to manufacture. For example, material layers that are placed on top of a semiconductor material may have both desirable and undesirable properties. Unfortunately, the manufacturing processes required to efficiently produce the semiconductor material may enhance the undesirable properties of other material layers. Therefore, material layers added to a photovoltaic device to improve efficiency may ultimately decrease its efficiency. [Overview of the project]

[0003]

[0003] Therefore, an alternative layer structure is needed for use in photovoltaic devices. [Brief explanation of the drawing]

[0004] [Figure 1]

[0004] This figure schematically illustrates a photovoltaic device according to one or more embodiments shown and described herein. [Figure 2]

[0005] This figure schematically shows a cross-section along 2-2 of the photovoltaic device in Figure 1 according to one or more embodiments shown and described herein. [Figure 3]

[0006] This figure schematically shows a substrate according to one or more embodiments shown and described herein. [Figure 4]

[0007] This figure schematically shows the transparent conductive layer of the photovoltaic device shown in Figures 1 and 2 according to one or more embodiments described herein. [Figure 5]

[0008] This figure schematically shows a cross-section of a tandem photovoltaic device according to one or more embodiments shown and described herein. [Modes for carrying out the invention]

[0005]

[0009] A photovoltaic device may be formed from a laminate of functional layers formed on a substrate. One or more functional layers may include thin films of material; that is, the photovoltaic device may be a thin-film photovoltaic device. A thin-film photovoltaic device may include an absorber layer for converting light into charge carriers and a conductive layer for collecting charge carriers. In some cases, the conductive layer may be formed in the direction of the back surface of the module relative to the absorber layer. In a single-junction device, the conductive layer may be located on the back surface of the module, and an opaque metal layer may be used as a component. However, such opaque layers may not be suitable for use as a conductive layer located between junctions in a multi-junction photovoltaic device or a tandem photovoltaic device. Embodiments provided herein relate to a transparent conductive layer and a photovoltaic device comprising the transparent conductive layer. The disclosed transparent conductive layer improves the reliability and durability of the current collector of the photovoltaic device and, at the same time, enables the use of the photovoltaic device in applications requiring transparency, such as windows, skylights, and tandem devices.

[0006]

[0010] Referring here to Figure 1, one embodiment of the photovoltaic device 100 is schematically shown. The photovoltaic device 100 may be configured to receive light and convert the light into electrical energy, for example, photons may be absorbed from light and converted into electric current via the photovoltaic effect. Thus, for discussion and clarification, the photovoltaic device 100 may define a front surface 102 configured to face a primary light source, such as the sun. Furthermore, the photovoltaic device 100 may also define a back surface 104 isolated from the front surface 102, for example, by multiple functional layers of material. Note that the term “light” can refer to various wavelengths of the electromagnetic spectrum, including ultraviolet (UV), infrared (IR), and wavelengths of the visible portion of the electromagnetic spectrum, but is not limited to these. “Sunlight” as used herein refers to light emitted by the sun.

[0007]

[0011] The photovoltaic device 100 may include multiple layers positioned between the front surface 102 and the back surface 104. As used herein, the term “layer” refers to the thickness of the material provided on the surface. Each layer may cover all or any portion of an adjacent surface. In some embodiments, the layers of the photovoltaic device 100 may be divided into an array of solar cells 200. For example, the photovoltaic device 100 may be scribed according to a plurality of series scribes 202 and a plurality of parallel scribes 204. The series scribes 202 extend along the length Y of the photovoltaic device 100 and can define the boundaries of the solar cells 200 along the length Y of the photovoltaic device 100. Multiple adjacent cells in the solar cells 200 may be connected in series along the width X of the photovoltaic device 100. In other words, a monolithic interconnect of multiple adjacent cells 200 may be formed adjacent to the series scribes 202. The parallel scribe 204 extends along the width X of the photovoltaic device 100 and can define the boundaries of the solar cells 200 along the width X of the photovoltaic device 100. During operation, current 205 can predominantly flow along the width X through the solar cells 200 connected in series by the series scribe 202. During operation, the parallel scribe 204 can limit the capacity of current 205 to flow along the length Y. The parallel scribe 204 is optional and may be configured to separate the series-connected solar cells 200 into groups 206 arranged along the length Y.

[0008]

[0012] Referring still to Figure 1, the parallel scribes 204 can electrically isolate groups 206 of series-connected solar cells 200. In some embodiments, groups 206 of solar cells 200 may be connected in parallel, for example, via electrical bussing. Optionally, the number of parallel scribes 204 may be configured to limit the maximum current generated by each group 206 of solar cells 200. In some embodiments, the maximum current generated by each group 206 may be about 200 milliamperes (mA) or less, for example, about 100 mA or less in one embodiment, about 75 mA or less in another embodiment, or about 50 mA or less in a further embodiment.

[0009]

[0013] Referring here to Figure 2, the layers of the photovoltaic device 100 may include a thin-film laminate provided on the substrate 110. The substrate 110 may be configured to facilitate the transmission of light to the photovoltaic device 100. The substrate 110 may be located on the front surface 102 of the photovoltaic device 100. Referring together to Figures 2 and 3, the substrate 110 may have a first surface 112 substantially facing the front surface 102 of the photovoltaic device 100 and a second surface 114 substantially facing the back surface 104 of the photovoltaic device 100. One or more layers of material may be located between the first surface 112 and the second surface 114 of the substrate 110.

[0010]

[0014] Referring to Figure 3, the substrate 110 may include a transparent layer 120 having a first surface 122 substantially facing the front surface 102 of the photovoltaic device 100 and a second surface 124 substantially facing the back surface 104 of the photovoltaic device 100. In some embodiments, the second surface 124 of the transparent layer 120 may form the second surface 114 of the substrate 110. The transparent layer 120 may be formed from a substantially transparent material, such as glass. Suitable glasses include soda-lime glass or any glass with a low iron content. The transparent layer 120 may have any preferred transmittance range, including, in some embodiments, about 250 nm to about 1,300 nm. The transparent layer 120 may also have any preferred transmittance percentage, including, for example, more than about 50% in one embodiment, more than about 60% in another embodiment, more than about 70% in yet another embodiment, more than about 80% in a further embodiment, or more than about 85% in a further embodiment. In one embodiment, the transparent layer 120 may be formed from glass with a transmittance of about 90% or more. Optionally, the substrate 110 may include a coating 126 applied to the first surface 122 of the transparent layer 120. The coating 126 may be configured to interact with light or to improve the durability of the substrate 110, but is not limited to, an anti-reflective coating, an anti-fouling coating, or a combination thereof.

[0011]

[0015] Referring again to FIG. 2, the photovoltaic device 100 may include a barrier layer 130 configured to reduce the diffusion of contaminants (e.g., sodium) from the substrate 110 that can cause degradation or delamination of other layers of the photovoltaic laminate. The barrier layer 130 may have a first surface 132 substantially facing the front surface 102 of the photovoltaic device 100 and a second surface 134 substantially facing the back surface 104 of the photovoltaic device 100. In some embodiments, the barrier layer 130 may be provided adjacent to the substrate 110. For example, the first surface 132 of the barrier layer 130 may be provided on the second surface 114 of the substrate 100. As used herein, the phrase "adjacent to" means that two layers are arranged continuously and without inclusions in at least a portion between the layers.

[0012]

[0016] Generally, the barrier layer 130 may be substantially transparent, thermally stable, have few pinholes, and have a high sodium blocking ability and good adhesion characteristics. Alternatively, or additionally, the barrier layer 130 may be configured to apply color suppression to light. The barrier layer 130 may include one or more layers of suitable materials including, but not limited to, tin oxide, silicon dioxide, silicon dioxide doped with aluminum, silicon nitride, or aluminum oxide. The barrier layer 130 may have any suitable thickness bounded by the first surface 132 and the second surface 134, including, for example, greater than about 100 Å in one embodiment, greater than about 150 Å in another embodiment, or less than about 200 Å in a further embodiment.

[0013]

[0017] Referring still to Figure 2, the photovoltaic device 100 may include a transparent conductive oxide (TCO) layer 140 configured to provide electrical contacts for transporting charge carriers generated by the photovoltaic device 100. The TCO layer 140 may have a first surface 142 substantially facing the front surface 102 of the photovoltaic device 100 and a second surface 144 substantially facing the back surface 104 of the photovoltaic device 100. In some embodiments, the TCO layer 140 may be provided adjacent to the barrier layer 130. For example, the first surface 142 of the TCO layer 140 may be provided on the second surface 134 of the barrier layer 130. Generally, the TCO layer 140 may be formed from one or more layers of an n-type semiconductor material that is substantially transparent and has a wide bandgap. Specifically, a wide bandgap can have a larger energy value compared to the energy of photons of light, which can reduce undesirable absorption of light. The TCO layer 140 may comprise one or more layers of a suitable material, including but not limited to tin dioxide, doped tin dioxide (e.g., F-SnO2), indium tin oxide, or cadmium stannate (Cd2SnO4). In embodiments in which the TCO layer 140 comprises cadmium stannate, the cadmium stannate may be provided in crystalline form. For example, the cadmium stannate may be deposited as a film and then subjected to an annealing process, thereby converting the thin film into a crystalline film.

[0014]

[0018] The photovoltaic device 100 may include a buffer layer 150 configured to provide an insulating layer between the TCO layer 140 and any adjacent semiconductor layer. The buffer layer 150 may have a first surface 152 substantially facing the front surface 102 of the photovoltaic device 100 and a second surface 154 substantially facing the back surface 104 of the photovoltaic device 100. In some embodiments, the buffer layer 150 may be provided adjacent to the TCO layer 140. For example, the first surface 152 of the buffer layer 150 may be provided on the second surface 144 of the TCO layer 140. The buffer layer 150 may include, but is not limited to, intrinsic tin dioxide, magnesium zinc oxide (e.g., Zn 1-x Mg x O), silicon dioxide (SiO2), aluminum oxide (Al2O3), aluminum nitride (AlN), zinc tin oxide, zinc oxide, silicon tin oxide, or a combination of any of these, and may include a material having a higher resistivity than the TCO layer 140. In some embodiments, the material of the buffer layer 150 may be configured to substantially match the bandgap of an adjacent semiconductor layer (e.g., an absorber). The buffer layer 150 may have any suitable thickness between the first surface 152 and the second surface 154, for example, greater than about 100 Å in one embodiment, about 100 Å to about 800 Å in another embodiment, or about 150 Å to about 600 Å in a further embodiment.

[0015]

[0019] Referring still to Figure 2, the photovoltaic device 100 may include an absorber layer 160 configured to form a pn junction within the photovoltaic device 100 in combination with another layer. Thus, the photons of absorbed light can dissociate electron-hole pairs, generating a carrier flow and yielding electrical energy. The absorber layer 160 may have a first surface 162 substantially facing the front surface 102 of the photovoltaic device 100 and a second surface 164 substantially facing the back surface 104 of the photovoltaic device 100. The thickness of the absorber layer 160 can be defined between the first surface 162 and the second surface 164. The thickness of the absorber layer 160 may be about 0.5 μm to about 10 μm, for example, about 1 μm to about 7 μm in one embodiment, about 1.5 μm to about 4 μm in another embodiment, and so on.

[0016]

[0020] According to embodiments described herein, the absorber layer 160 may be formed from a p-type semiconductor material having excess positive charge carriers, i.e., holes or acceptors. The absorber layer 160 may include any suitable p-type semiconductor material, such as a group II-VI semiconductor like cadmium and tellurium. Further examples include, but are not limited to, semiconductor materials containing cadmium, zinc, tellurium, selenium, or any combination thereof. In some embodiments, the absorber layer 160 is a ternary of cadmium, selenium, and tellurium (e.g., CdSe x Te 1-x ), or a compound containing cadmium, selenium, tellurium, and one or more additional elements (e.g., CdZnSeTe). The absorber layer 160 may further contain one or more dopants. The photovoltaic device 100 provided herein may contain multiple absorber materials.

[0017]

[0021] In embodiments in which the absorber layer 160 contains tellurium and cadmium, the average atomic percentage of tellurium in the absorber layer 160 may be between approximately 25 atomic percentages and approximately 50 atomic percentages, for example, more than approximately 30 atomic percentages and less than approximately 50 atomic percentages in one embodiment, more than approximately 40 atomic percentages and less than approximately 50 atomic percentages in a further embodiment, or more than approximately 47 atomic percentages and less than approximately 50 atomic percentages in yet another embodiment. Alternatively, the average atomic percentage of tellurium in the absorber layer 160 may be more than approximately 45 atomic percentages, for example, more than approximately 49% in one embodiment. It should be noted that the average atomic percentages described herein are representative of the absorber layer 160 as a whole, and the atomic percentage of material at a particular location within the absorber layer 160 may be gradientd with respect to the thickness compared to the overall composition of the absorber layer 160. For example, the absorber layer 160 may have a gradient composition.

[0018]

[0022] In embodiments in which the absorber layer 160 contains selenium and tellurium, the average atomic percentage of selenium in the absorber layer 160 may be greater than about 0 atomic percentages and less than about 25 atomic percentages, for example, greater than about 1 atomic percentage and less than about 20 atomic percentages in one embodiment, greater than about 1 atomic percentage and less than about 15 atomic percentages in another embodiment, or greater than about 1 atomic percentage and less than about 8 atomic percentages in a further embodiment. It should be noted that the concentrations of tellurium, selenium, or both can be gradient by the thickness of the absorber layer 160. For example, if the absorber layer 160 contains a compound (Se) containing selenium in a mole fraction of x and tellurium in a mole fraction of 1-x x Te 1-x If this is included, x may vary within the absorber layer 160 depending on the distance from the first surface 162 of the absorber layer 160.

[0019]

[0023] Referring further to Figure 2, the absorber layer 160 may be doped with dopants configured to manipulate the charge carrier concentration. In some embodiments, the absorber layer 160 may be doped with Group V dopants such as arsenic, phosphorus, antimony, or combinations thereof. Alternatively, the absorber layer 160 may be doped with Group IB dopants such as copper, silver, gold, or combinations thereof. The total density of dopants in the absorber layer 160 can be controlled. Furthermore, the amount of dopant may vary depending on the distance of the absorber layer 160 from the first surface 162.

[0020]

[0024] According to embodiments provided herein, a pn junction may be formed by providing an absorber layer 160 in close proximity to a portion of the photovoltaic device 100 having excess negative charge carriers, i.e., electrons or donors. In some embodiments, the absorber layer 160 may be provided adjacent to the n-type semiconductor material. Alternatively, one or more intervening layers may be provided between the absorber layer 160 and the n-type semiconductor material. In some embodiments, the absorber layer 160 may be provided adjacent to a buffer layer 150. For example, the first surface 162 of the absorber layer 160 may be provided on the second surface 154 of the buffer layer 150.

[0021]

[0025] The photovoltaic device 100 may include a back contact layer 170 configured to mitigate undesirable dopant degradation and provide electrical contacts to the absorber layer 160. The back contact layer 170 may have a first surface 172 substantially facing the front surface 102 of the photovoltaic device 100 and a second surface 174 substantially facing the back surface 104 of the photovoltaic device 100. The thickness of the back contact layer 170 can be defined between the first surface 172 and the second surface 174. The thickness of the back contact layer 170 may be about 5 nm to about 200 nm, for example, about 10 nm to about 50 nm in one embodiment.

[0022]

[0026] In some embodiments, the back contact layer 170 may be provided adjacent to the absorber layer 160. For example, the first surface 172 of the back contact layer 170 may be provided on the second surface 164 of the absorber layer 160. In some embodiments, the back contact layer 170 may include a combination of group I, II, and VI materials, such as one or more layers containing zinc and tellurium in various compositions. Further exemplary materials include, but are not limited to, a two-layer structure of cadmium zinc telluride and zinc telluride, or zinc telluride doped with a group V dopant such as nitrogen. The thin-film junction 176 may be defined as a thin-film laminate that primarily contributes to the photovoltaic effect. For example, in some embodiments, the thin-film junction 176 may include a transparent conductive oxide layer 140, a buffer layer 150, an absorber layer 160, a back contact layer 170, or a combination thereof.

[0023]

[0027] Referring together to Figures 2 and 4, the photovoltaic device 100 may include a transparent conductive layer 180 configured to provide electrical contacts to the back contact layer 170, the absorber layer 160, or both. The transparent conductive layer 180 may have a first surface 182 substantially facing the front surface 102 of the photovoltaic device 100 and a second surface 184 substantially facing the back surface 104 of the photovoltaic device 100. In some embodiments, the transparent conductive layer 180 may be provided adjacent to the back contact layer 170 or the absorber layer 160. For example, the first surface 182 of the transparent conductive layer 180 may be provided on the second surface 174 of the back contact layer 170 or the second surface 162 of the absorber layer 160. The thickness of the transparent conductive layer 180 may be defined between the first surface 182 and the second surface 184. The thickness of the transparent conductive layer 180 may be less than approximately 500 nm, for example, in one embodiment, about 40 nm to about 400 nm, or about 60 nm to about 350 nm.

[0024]

[0028] According to embodiments provided herein, the transparent conductive layer 180 may include one or more functional layers of the material. In some embodiments, the conductive layer 180 may have an average transmittance of more than about 50% for light having wavelengths of 300 nm to 1300 nm. Optionally, the conductive layer 180 may have an average transmittance of more than about 50% for light having wavelengths of 800 nm to 1300 nm, for example, more than about 85% in one embodiment, more than about 90% in another embodiment, or more than about 95% in a further embodiment. The transparent conductive layer 180 may include a diffusion barrier layer 210 that can operate to restrict the diffusion of metallic species into the active region of the cell 200, such as an absorber layer 160. Diffusion of metallic species into the absorber layer 160 may reduce the conversion efficiency of the cell 200. Such degradation and performance reduction may be particularly associated with high temperature and / or high humidity environments. Therefore, the use of a suitable diffusion barrier 210 can improve the performance of the photovoltaic device 100.

[0025]

[0029] The diffusion barrier layer 210 may have a first surface 212 substantially facing the front surface 102 of the photovoltaic device 100 and a second surface 214 substantially facing the back surface 104 of the photovoltaic device 100. The thickness of the diffusion barrier layer 210 can be defined between the first surface 212 and the second surface 214. The thickness of the diffusion barrier layer 210 may be less than about 125 nm, for example, about 2 nm to about 100 nm in one embodiment, or about 5 nm to about 50 nm in another embodiment.

[0026]

[0030] In some embodiments, the diffusion barrier layer 210 may be provided adjacent to the back contact layer 170. For example, the first surface 212 of the diffusion barrier layer 210 may be provided on the second surface 174 of the back contact layer 170. Thus, in some embodiments, the first surface 182 of the back contact layer 180 may be formed by the first surface 212 of the diffusion barrier layer 210. Generally, the diffusion barrier layer 210 may be formed of a material having a suitable permeability that can be doped in a "+" type. For example, about 1 × 1016 cm -3 A larger charge density may be considered to be of the "+" type. In some embodiments, the diffusion barrier layer 210 may be doped n+. In an alternative embodiment, the diffusion barrier layer 210 may be doped p+. The boundaries are not exact, but if the electron donor carriers are on the order of about 1×10 11 cm -3 ~ about 1×10 16 cm -3 and are present, the material may be considered n-type, and if the donor carrier density is greater than about 1×10 16 cm -3 , it may be considered n+-type. Similarly, a material is considered p-type if the electron acceptor carriers (i.e., "holes") are on the order of about 1×10 11 cm -3 ~ about 1×10 16 cm -3 and are present, and p+-type if the acceptor carrier density is greater than about 1×10 16 cm -3 . Regardless of the absolute carrier density, the boundaries are not exact and there may be overlap since a layer may be p+ with respect to a p-type layer (or n+ with respect to an n-type layer) if the carrier concentration is at least two orders of magnitude (i.e., 100 times) higher. Further, a charge density greater than about 1×10 18 cm -3 may be considered to be of the "++" type. Thus, either an n-type or p-type layer may be "++" with respect to a layer of the same type that is itself "+" with respect to a third layer if the ++ layer has a carrier density of more than 100 times that of the + layer.

[0027]

[0031] Suitable materials for the diffusion barrier layer 210 include, for example, titanium oxynitride (TiN x O y ) or molybdenum oxynitride (MoN x O yThe alloy may also contain refractory oxynitrides such as ). Although not bound by theory, the applicant has found that as the amount of oxygen in the alloy increases, the oxynitrides may exhibit improved optical properties, i.e., increased transmittance. However, it is also thought that the increased oxygen may further decrease electrical conductivity. Another group of materials suitable for use in the transparent diffusion barrier 310 include, for example, tin oxide (SnO2), zinc oxide (ZnO), indium tin oxide (In( 2-x )Sn x Examples include transparent conductive oxides such as O3, cadmium oxide (CdO), and cadmium stannate (Cd2SnO4). These transparent conductive oxides may be doped with F, Al, In, Ga, Ti, and other impurities to alter their electrical and optical properties.

[0028]

[0032] Unexpectedly, cadmium stannate (Cd2SnO4) was found to exhibit a superior combination of diffusion barrier properties, optical properties, and electrical properties compared to other transparent conductive oxides. Furthermore, it was discovered that amorphous cadmium stannate may be used in the diffusion barrier layer 210. As used herein, the term "amorphous" refers to a solid lacking long-range order. Generally, amorphous cadmium stannate may be formed by depositing layers of material without transforming the layer's morphology through a heat treatment process. For example, amorphous cadmium stannate may be deposited at relatively low temperatures and without post-deposition annealing. In some embodiments, amorphous cadmium stannate is Cd x It may be formed from SnO4 material (0.5 ≤ x ≤ 2).

[0029]

[0033] Referring still to Figures 2 and 4, the transparent conductive layer 180 may include a high conductivity layer 220 configured to provide a low device series resistance. The high conductivity layer 220 may have a first surface 222 substantially oriented toward the front surface 102 of the photovoltaic device 100 and a second surface 224 substantially oriented toward the back surface 104 of the photovoltaic device 100. The thickness of the high conductivity layer 220 can be defined between the first surface 222 and the second surface 224. The thickness of the high conductivity layer 220 may be less than about 300 nm, for example, about 30 nm to about 300 nm in one embodiment, about 50 nm to about 250 nm in another embodiment, or about 100 nm to about 250 nm in a further embodiment.

[0030]

[0034] In some embodiments, the high conductivity layer 220 may be positioned further away from the absorber layer 160 or the back contact layer 170 compared to the diffusion barrier layer 210. Therefore, the diffusion barrier layer 210 may be positioned between the absorber layer 160 and the high conductivity layer 220, or between the back contact layer 170 and the high conductivity layer 220. Specifically, in some embodiments, the high conductivity layer 220 may be provided adjacent to the high conductivity layer. For example, the first surface 222 of the high conductivity layer 220 may be provided on the second surface 214 of the diffusion barrier layer 210. Generally, the high conductivity layer 220 may be formed from a material having a suitable transmittance that can be doped to the "++" type. In some embodiments, the diffusion barrier layer 210 may be doped to n++. Therefore, the high conductivity layer 220 may contain a transparent conductive oxide that is degenerately doped. In some embodiments, the high conductivity layer 220 may be doped with n++ by itself or with an oxide dopant. Suitable oxide dopants include, but are not limited to, In2O3, Ga2O3, TiO2, Dy2O3, SnO2, Y2O3, Al2O3, or any combination thereof. The applicant has found that cadmium oxide (CdO), such as indium oxide-doped cadmium oxide (CdO:In2O3) or gallium oxide-doped cadmium oxide (CdO:Ga2O3), has relatively high electrical mobility compared to other transparent conductive oxides with suitable optical properties. Thus, embodiments of the high conductivity layer 220 containing cadmium oxide have shown relatively high packing density and improved photovoltaic performance.

[0031]

[0035] According to embodiments provided herein, the transparent conductive layer 180 may include a capping layer 230 that can operate to reduce corrosion of the high conductivity layer 220 in a high-temperature, high-humidity environment. The capping layer 230 may have a first surface 232 substantially oriented toward the front surface 102 of the photovoltaic device 100 and a second surface 234 substantially oriented toward the back surface 104 of the photovoltaic device 100. The thickness of the capping layer 230 can be defined between the first surface 232 and the second surface 234. The thickness of the capping layer 230 may be less than about 125 nm, for example, about 2 nm to about 100 nm in one embodiment, or about 5 nm to about 50 nm in another embodiment.

[0032]

[0036] In some embodiments, the capping layer 230 may be located further away from the absorber layer 160 or the back contact layer 170 compared to the high conductivity layer 220. Thus, the high conductivity layer 220 may be located between the diffusion barrier layer 210 and the capping layer 230. Specifically, in some embodiments, the capping layer 230 may be provided adjacent to the high conductivity layer 220. For example, the first surface 232 of the capping layer 230 may be provided on the second surface 224 of the high conductivity layer 220. The capping layer 230 may contain a transparent conductive oxide, such as cadmium stannate. In some embodiments, the capping layer may contain amorphous cadmium stannate.

[0033]

[0037] Referring again to Figure 2, the photovoltaic device 100 may include a back support 190 configured to form a housing for the photovoltaic device 100 in combination with the substrate 110. The back support 190 may be located on the back surface 104 of the photovoltaic device 100. The back support 190 may include any preferred material, such as borosilicate glass, float glass, soda-lime glass, carbon fiber, or polycarbonate. Alternatively, the back support 190 may be any preferred material, such as a polymer-based back sheet. The back support 190 and the substrate 110 can protect the various layers of the photovoltaic device 100 from exposure to moisture and other environmental hazards.

[0034]

[0038] Referring to Figure 5, a tandem photovoltaic device 300 is schematically shown. The tandem photovoltaic device 300 may include a tandem cell 302, which may be formed by scribing as disclosed above with respect to the photovoltaic device 100's solar cell 200. The tandem cell 300 may include a thin-film junction 176. The thin-film junction 176 may be electrically connected to the second junction 310 via a transparent conductive layer 180 and optionally an electric bus 236. As used herein, the phrase “electrically connected” may mean that the components, as a pair, form substantial ohmic contact with each other, either directly or indirectly through one or more additional components. Thus, current can flow between the second junction 310 and the thin-film junction 176 via the electrical connection. In some embodiments, the second junction 310 and the thin-film junction 176 may be electrically connected in series. Alternatively, the second junction 310 and the thin-film junction 176 may be electrically connected in parallel, for example, via one or more additional components or conductors. In some embodiments, the thin-film junction 176 may be positioned closer to the front surface 102 of the tandem photovoltaic device 300 than the second junction 310. The transparent conductive layer 180 may be positioned between the thin-film junction 176 and the second junction 310.

[0035]

[0039] The second junction 310 may be configured to convert light into electrical energy via the photovoltaic effect. The second junction 310 may include a different semiconductor from the absorber layer 160 of the thin-film junction 176, such as amorphous silicon (a-Si), crystalline silicon (c-Si), or copper indium gallium selenide (CIGS). The thin-film junction 176 and the second junction 310 may be configured to absorb different ranges of wavelengths. For example, the thin-film junction 176 may be configured to absorb light with shorter wavelengths than the second junction 310. In some embodiments, the average quantum efficiency of the thin-film junction 176 in the 800 nm to 1,300 nm range may be less than about 20%, for example, less than about 10% in one embodiment or less than about 5% in another embodiment. Furthermore, the average quantum efficiency of the second junction 310 in the 800 nm to 1,300 nm range may be greater than about 50%, for example, greater than about 60% in one embodiment or greater than about 65% in another embodiment.

[0036]

[0040] It should be understood here that the functional layer of the transparent conductive layer can provide improved light transmittance while offering comparable electrical functionality and reliability compared to known opaque electrical contacts. Therefore, the embodiments provided herein can improve the practicality of photovoltaic devices. For example, the laminate of diffusion barrier, high conductivity layer, and capping layer described herein may be used as a tunnel junction in a tandem photovoltaic device. Alternatively, the laminate of diffusion barrier, high conductivity layer, and capping layer described herein may be used as a transparent back electrical contact in a transparent module or a double-sided module.

[0037]

[0041] According to embodiments described herein, a tandem photovoltaic device may include a thin film junction, a second junction, and a transparent conductive layer. The thin film junction may include an absorber layer containing cadmium and tellurium. The second junction may be electrically connected to the thin film junction. Current can flow between the second junction and the thin film junction. The transparent conductive layer may be located between the thin film junction and the second junction. Current can flow through the transparent conductive layer. The transparent conductive layer may include a high conductivity layer and an adjacent layer. The high conductivity layer may contain cadmium oxide of the "++" type, either by itself or by doping with an oxide dopant. The adjacent layer is in contact with the high conductivity layer.

[0038]

[0042] In another embodiment, the tandem photovoltaic device may include a thin film junction, a second junction, and a transparent conductive layer. The thin film junction may include an absorber layer containing cadmium and tellurium. The second junction may be electrically connected to the thin film junction. Current can flow between the second junction and the thin film junction. The transparent conductive layer may be located between the thin film junction and the second junction. Current can flow through the transparent conductive layer. The transparent conductive layer may include a high conductivity layer and an adjacent layer. The high conductivity layer may be doped with n++. The adjacent layer is in contact with the high conductivity layer. The adjacent layer contains amorphous cadmium stannate.

[0039]

[0043] In yet another embodiment, the tandem photovoltaic device may include a thin film junction, a second junction, and a transparent conductive layer. The thin film junction may include an absorber layer containing cadmium and tellurium. The second junction may be electrically connected to the thin film junction. Current can flow between the second junction and the thin film junction. The transparent conductive layer may be placed between the thin film junction and the second junction. Current can flow through the transparent conductive layer. The transparent conductive layer may contain amorphous cadmium stannate.

[0040]

[0044] In further embodiments, the photovoltaic device may include a thin film junction and a transparent conductive layer. The thin film junction may include an absorber layer containing cadmium and tellurium. The transparent conductive layer may form at least a portion of a series connection with the thin film junction. The transparent conductive layer may include a high conductivity layer and an adjacent layer. The high conductivity layer may be doped in the "++" type. The adjacent layer may be in contact with the high conductivity layer.

[0041]

[0045] In another embodiment, the photovoltaic device may include a thin film junction and a transparent conductive layer. The thin film junction may include an absorber layer containing cadmium and tellurium. The transparent conductive layer may form at least a portion of a series connection with the thin film junction. The transparent conductive layer may include a high conductivity layer and an adjacent layer. The high conductivity layer may contain indium oxide-doped cadmium oxide. The adjacent layer may be in contact with the high conductivity layer. The adjacent layer may contain amorphous cadmium stannate.

[0042]

[0046] In yet another embodiment, the photovoltaic device may include a thin film junction and a transparent conductive layer. The transparent conductive layer can conduct charge carriers from the thin film junction. The transparent conductive layer may include a high conductivity layer and an adjacent layer. The adjacent layer may be in contact with the high conductivity layer. The high conductivity layer contains indium oxide-doped cadmium oxide.

[0043]

[0047] In this specification, the terms “substantially” and “about” may be used to express the degree of inherent uncertainty that may arise from any quantitative comparison, value, measurement, or other expression. These terms are also used in this specification to express the degree to which quantitative expressions may vary from the references given without altering the fundamental function of the subject matter in question.

[0044]

[0048] While specific embodiments have been illustrated and described herein, it should be understood that various other changes and modifications may be made without departing from the spirit and scope of the claimed subject matter. Furthermore, while various aspects of the claimed subject matter have been described herein, such aspects do not need to be used in combination. Accordingly, the appended claims are intended to encompass all such changes and modifications that fall within the scope of the claimed subject matter. [Modes of the Invention] [1] A tandem photovoltaic device comprising a thin film bond, a second bond, and a transparent conductive layer, The thin film junction comprises an absorber layer containing cadmium and tellurium; The second junction is electrically connected to the thin film junction, thereby allowing current to flow between the second junction and the thin film junction; and The transparent conductive layer is positioned between the thin film junction and the second junction, and the current flows through the transparent conductive layer, The transparent conductive layer comprises a high conductivity layer and an adjacent layer, The adjacent layer is in contact with the high conductivity layer, and The aforementioned high conductivity layer contains cadmium oxide of the "++" type, either by itself or through doping with an oxide dopant. The above-mentioned tandem photovoltaic device. [2] The tandem photovoltaic device according to claim 1, wherein the adjacent layer contains amorphous cadmium stannate. [3] The tandem photovoltaic device according to claim 2, wherein the cadmium oxide is doped to n++ with an oxide dopant. [4] The tandem photovoltaic device according to claim 3, wherein the oxide dopant is In2O3. [5] The tandem photovoltaic device according to claim 3, wherein the oxide dopant is Ga2O3. [6] The transparent conductive layer comprises a capping layer in contact with the high conductivity layer, The tandem photovoltaic device according to claim 2, wherein the transparent conductive layer is located between the adjacent layer and the capping layer. [7] The tandem photovoltaic device according to claim 6, wherein the capping layer contains amorphous cadmium stannate. [8] The transparent conductive layer comprises a diffusion barrier layer in contact with the high conductivity layer, The tandem photovoltaic device according to claim 2, wherein the transparent conductive layer is located between the adjacent layer and the diffusion barrier layer. [9] The tandem photovoltaic device according to claim 8, wherein the diffusion barrier layer contains amorphous cadmium stannate.

[10] The tandem photovoltaic device according to claim 1, wherein the high conductivity layer is thicker than the adjacent layer.

[11] The tandem photovoltaic device according to claim 1, wherein the thickness of the adjacent layer is less than 125 nm.

[12] The tandem photovoltaic device according to claim 1, wherein the thickness of the high conductivity layer is less than 300 nm.

[13] The tandem photovoltaic device according to claim 1, wherein the thickness of the transparent conductive layer is greater than 40 nm and less than 400 nm.

[14] The tandem photovoltaic device according to claim 1, wherein the transparent conductive layer has an average transmittance of more than 85% for light having a wavelength of 800 nm to 1,300 nm.

[15] The tandem photovoltaic device according to claim 1, wherein the average quantum efficiency of the thin film junction in the range of 800 nm to 1,300 nm is less than 20%.

[16] The tandem photovoltaic device according to claim 15, wherein the absorber layer of the thin film junction contains zinc.

[17] The tandem photovoltaic device according to claim 15, wherein the absorber layer of the thin film junction contains selenium.

[18] The thin film bonding comprises a back contact layer, The back contact layer is disposed between the absorber layer and the transparent conductive layer, and The tandem photovoltaic device according to claim 1, wherein the back contact layer comprises zinc and tellurium.

[19] The tandem photovoltaic device according to claim 1, wherein the average quantum efficiency of the second junction in the range of 800 nm to 1,300 nm exceeds 50%.

[20] The tandem photovoltaic device according to claim 19, wherein the second junction comprises amorphous silicon or crystalline silicon. [twenty one] The tandem photovoltaic device according to claim 19, wherein the second junction comprises copper indium gallium selenide. [twenty two] The thin film bonding comprises a transparent conductive oxide layer, and The tandem photovoltaic device according to claim 1, wherein the absorber layer of the thin film junction is disposed between the transparent conductive oxide layer and the transparent conductive layer. [twenty three] The tandem photovoltaic device according to claim 22, wherein the transparent conductive oxide layer comprises indium tin oxide. [twenty four] The tandem photovoltaic device according to claim 22, wherein the transparent conductive oxide layer contains cadmium stannate. [twenty five] The tandem photovoltaic device according to claim 24, wherein the cadmium stannate is crystalline.

[26] A tandem photovoltaic device comprising a thin film bond, a second bond, and a transparent conductive layer, The thin film junction comprises an absorber layer containing cadmium and tellurium; The second junction is electrically connected to the thin film junction, thereby allowing current to flow between the second junction and the thin film junction; and The transparent conductive layer is positioned between the thin film junction and the second junction, and the current flows through the transparent conductive layer, The transparent conductive layer comprises a high conductivity layer and an adjacent layer, The aforementioned high conductivity layer is doped with n++, The adjacent layer is in contact with the high conductivity layer, and The adjacent layer contains amorphous cadmium stannate. The above-mentioned tandem photovoltaic device.

[27] A tandem photovoltaic device comprising a thin film bond, a second bond, and a transparent conductive layer, The thin film junction comprises an absorber layer containing cadmium and tellurium; The second junction is electrically connected to the thin film junction, thereby allowing current to flow between the second junction and the thin film junction; and The transparent conductive layer is positioned between the thin film junction and the second junction, and the current flows through the transparent conductive layer, wherein the transparent conductive layer contains amorphous cadmium stannate. The above-mentioned tandem photovoltaic device.

[28] A tandem photovoltaic device comprising a thin film junction and a transparent conductive layer, The thin film junction comprises an absorber layer containing cadmium and tellurium; and The transparent conductive layer forms at least a portion of the electrical connection with the thin film junction, The transparent conductive layer contains amorphous cadmium stannate in a photovoltaic device.

[29] A tandem photovoltaic device comprising a thin film junction and a transparent conductive layer, The thin film junction comprises an absorber layer containing cadmium and tellurium; and The transparent conductive layer forms at least a part of the series connection with the thin film junction, where The transparent conductive layer comprises a high conductivity layer and an adjacent layer, The aforementioned high conductivity layer is doped in the "++" type, and The adjacent layer is in contact with the high conductivity layer. The above-mentioned tandem photovoltaic device.

[30] A tandem photovoltaic device comprising a thin film junction and a transparent conductive layer, The thin film junction comprises an absorber layer containing cadmium and tellurium; and The transparent conductive layer forms at least a part of the series connection with the thin film junction, where The transparent conductive layer comprises a high conductivity layer and an adjacent layer, The aforementioned high conductivity layer contains cadmium oxide doped with indium oxide, The adjacent layer is in contact with the high conductivity layer, and The adjacent layer contains cadmium stanate, The above.

[31] Thin film bonding; and A transparent conductive layer conducts charge carriers from the thin film junction. A tandem photovoltaic device comprising, here The transparent conductive layer comprises a high conductivity layer and an adjacent layer, The adjacent layer is in contact with the high conductivity layer, and The aforementioned high conductivity layer contains cadmium oxide doped with indium oxide, The above-mentioned photovoltaic device.

[32] The tandem photovoltaic device or photovoltaic device according to any one of claims 1 and 26 to 31, wherein the adjacent layer contains amorphous cadmium stannate.

[33] The tandem photovoltaic device or photovoltaic device according to claim 32, wherein the cadmium oxide is doped to n++ with an oxide dopant.

[34] The tandem photovoltaic device or photovoltaic device according to claim 33, wherein the oxide dopant is In2O3.

[35] The tandem photovoltaic device or photovoltaic device according to claim 33, wherein the oxide dopant is Ga2O3.

[36] The transparent conductive layer comprises a capping layer in contact with the high conductivity layer, The tandem photovoltaic device or photovoltaic device according to any one of claims 1 and 26 to 35, wherein the transparent conductive layer is located between the adjacent layer and the capping layer.

[37] The tandem photovoltaic device or photovoltaic device according to claim 36, wherein the capping layer contains amorphous cadmium stannate.

[38] The transparent conductive layer comprises a diffusion barrier layer in contact with the high conductivity layer, and The tandem photovoltaic device or photovoltaic device according to any one of claims 1 and 26 to 37, wherein the transparent conductive layer is located between the adjacent layer and the diffusion barrier layer.

[39] The tandem photovoltaic device or photovoltaic device according to claim 38, wherein the diffusion barrier layer contains amorphous cadmium stannate.

[40] The tandem photovoltaic device or photovoltaic device according to any one of claims 1 and 26 to 39, wherein the high conductivity layer is thicker than the adjacent layer.

[41] A tandem photovoltaic device or photovoltaic device according to any one of claims 1 and 26 to 40, wherein the thickness of the adjacent layer is less than 125 nm.

[42] A tandem photovoltaic device or photovoltaic device according to any one of claims 1 and 26 to 41, wherein the thickness of the high conductivity layer is less than 300 nm.

[43] A tandem photovoltaic device or photovoltaic device according to any one of claims 1 and 26 to 42, wherein the thickness of the transparent conductive layer is greater than 40 nm and less than 400 nm.

[44] The tandem photovoltaic device or photovoltaic device according to any one of claims 1 and 26 to 43, wherein the transparent conductive layer has an average transmittance of more than 85% for light having a wavelength of 800 nm to 1,300 nm.

[45] A tandem photovoltaic device or photovoltaic device according to any one of claims 1 and 26 to 44, wherein the average quantum efficiency of the thin film junction in the range of 800 nm to 1,300 nm is less than 20%.

[46] The tandem photovoltaic device or photovoltaic device according to any one of claims 1 and 26 to 45, wherein the absorber layer of the thin film junction contains zinc.

[47] The tandem photovoltaic device or photovoltaic device according to any one of claims 1 and 26 to 46, wherein the absorber layer of the thin film junction contains selenium.

[48] The thin film bonding comprises a back contact layer, The back contact layer is disposed between the absorber layer and the transparent conductive layer, and The back contact layer comprises zinc and tellurium. A tandem photovoltaic device or photovoltaic device according to any one of claims 1 and 26 to 47.

[49] A tandem photovoltaic device according to any one of claims 1, 26 to 27 and 32 to 48, wherein the average quantum efficiency of the second junction in the range of 800 nm to 1,300 nm exceeds 50%.

[50] The tandem photovoltaic device according to claim 49, wherein the second junction comprises amorphous silicon or crystalline silicon.

[51] The tandem photovoltaic device according to claim 49, wherein the second junction comprises copper indium gallium selenide.

[52] The thin film bonding comprises a transparent conductive oxide layer, and The absorber layer of the thin film junction is disposed between the transparent conductive oxide layer and the transparent conductive layer. A tandem photovoltaic device or photovoltaic device according to any one of claims 1 and 26 to 51.

[53] The tandem photovoltaic device or photovoltaic device according to claim 52, wherein the transparent conductive oxide layer comprises indium tin oxide.

[54] The tandem photovoltaic device or photovoltaic device according to claim 52, wherein the transparent conductive oxide layer contains cadmium stannate.

[55] The tandem photovoltaic device or photovoltaic device according to claim 54, wherein the cadmium stannate is crystalline.

Claims

1. A tandem photovoltaic device comprising a thin film bond, a second bond, and a transparent conductive layer, The thin film junction comprises an absorber layer containing cadmium and tellurium; The second junction is electrically connected to the thin-film junction, wherein the second junction is closer to the back surface of the tandem photovoltaic device than the thin-film junction; and The transparent conductive layer is placed between the thin film bond and the second bond, where The transparent conductive layer comprises a high conductivity layer, a diffusion barrier layer, and a capping layer. The diffusion barrier layer contains cadmium stannate, The capping layer contains cadmium stannate, The aforementioned high conductivity layer is 1 × 10 １８ cm ー３ It contains cadmium oxide with a higher charge density, and The high conductivity layer is located between the diffusion barrier layer and the capping layer. The above-mentioned tandem photovoltaic device.

2. The diffusion barrier layer and one of the capping layers contain amorphous cadmium stannate, where the amorphous cadmium stannate is Cd ｘ SnO ４ The tandem photovoltaic device according to claim 1, wherein the material is (wherein x is a value in the range of 0.5 to 2).

3. The cadmium oxide in the high conductivity layer is doped to n++ with an oxide dopant, and the cadmium oxide doped to n++ with the oxide dopant is 1 × 10 １８ cm ー３ A tandem photovoltaic device according to claim 1 or 2, having a larger charge density.

4. The aforementioned oxide dopant is In ２ O ３ The tandem photovoltaic device according to claim 3.

5. where the oxide dopant is Ga ２ O ３ The tandem-type photovoltaic device according to claim 3

6. The tandem photovoltaic device according to any one of claims 1 to 5, wherein the capping layer is in contact with the high conductivity layer.

7. The tandem photovoltaic device according to any one of claims 1 to 6, wherein the capping layer contains amorphous cadmium stannate.

8. The diffusion barrier layer is in contact with the high conductivity layer, and The tandem photovoltaic device according to any one of claims 1 to 7, wherein the diffusion barrier layer is in contact with the back contact layer of the thin film bonding.

9. The tandem photovoltaic device according to claim 8, wherein the diffusion barrier layer contains amorphous cadmium stannate.

10. The tandem photovoltaic device according to claim 1, wherein the high conductivity layer is thicker than at least one of the diffusion barrier layer or the capping layer, and the thickness of the high conductivity layer is less than 300 nm.

11. The tandem photovoltaic device according to any one of claims 1 to 10, wherein the thickness of the transparent conductive layer is greater than 40 nm and less than 400 nm.

12. The tandem photovoltaic device according to any one of claims 1 to 11, wherein the transparent conductive layer has an average transmittance of more than 85% for light having a wavelength of 800 nm to 1,300 nm.

13. The tandem photovoltaic device according to any one of claims 1 to 12, wherein the average quantum efficiency of the thin film junction in light having a wavelength of 800 nm to 1,300 nm is less than 20%.

14. The tandem photovoltaic device according to any one of claims 1 to 13, wherein the absorber layer of the thin film junction comprises at least one of zinc and selenium.

15. The thin film bonding comprises a back contact layer, and The back contact layer is disposed between the absorber layer and the transparent conductive layer, and The tandem photovoltaic device according to any one of claims 1 to 14, wherein the back contact layer comprises zinc and tellurium.

16. The average quantum efficiency of the second junction is over 50% for light with wavelengths of 800 nm to 1,300 nm, and The tandem photovoltaic device according to any one of claims 1 to 15, wherein the second junction includes a semiconductor different from the absorber layer of the thin film junction.

17. The thin film bonding comprises a transparent conductive oxide layer, and The tandem photovoltaic device according to any one of claims 1 to 16, wherein the absorber layer of the thin film junction is disposed between the transparent conductive oxide layer and the transparent conductive layer.

18. The tandem photovoltaic device according to claim 17, wherein the transparent conductive oxide layer contains indium tin oxide.

19. The tandem photovoltaic device according to claim 17, wherein the transparent conductive oxide layer contains cadmium stannate, and the cadmium stannate is crystalline.

20. A tandem photovoltaic device comprising a thin film bond, a second bond, and a transparent conductive layer, The thin film junction comprises an absorber layer containing cadmium and tellurium; The second junction is electrically connected to the thin-film junction; and The transparent conductive layer is disposed between the thin film bond and the second bond, and the transparent conductive layer comprises a high conductivity layer, a diffusion barrier layer and a capping layer. The diffusion barrier layer contains cadmium stannate, The capping layer contains cadmium stannate, The aforementioned high conductivity layer is 1 × 10 １８ cm ー３ It contains cadmium oxide with a higher charge density, and The high conductivity layer is located between the diffusion barrier layer and the capping layer. The above-mentioned tandem photovoltaic device.

21. The second junction and the thin film junction are electrically connected in series, and The tandem photovoltaic device according to any one of claims 1 to 20, wherein the transparent conductive layer forms at least a portion of the series connection with the thin film junction.

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