Buffer layers in photovoltaic devices with group V doping.

Abstract

To provide alternative buffer layers for use with an absorber layer doped with a group V p-type dopant.SOLUTION: A photovoltaic device 100 includes a transparent conductive oxide (TCO) layer 140 configured to provide an electrical contact to transport charge carriers generated by the photovoltaic device 100. The TCO layer 140 can have a first surface 142 substantially facing an energy side 102 of the photovoltaic device 100, and a second surface 144 substantially facing an opposing side 104 of the photovoltaic device 100. The TCO layer 140 can be provided adjacently to a buffer layer 130. The photovoltaic device 100 can include a buffer layer 150 configured to provide a less conductive layer between the TCO layer 140 and any adjacent semiconductor layers.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This specification relates generally to photovoltaic devices having a buffer layer compatible with a group V dopant, and more specifically to photovoltaic devices having a buffer layer compatible with a group V dopant adjacent to an absorber layer that is p-type doped with a group V dopant. [Background technology]

[0002]

[0002] Photovoltaic devices generate electrical power by converting light into direct current using semiconductor materials that exhibit the photovoltaic effect. Certain types of semiconductor materials can be difficult to manufacture. For example, thin film layers disposed adjacent to the semiconductor material can cause the photovoltaic device to be inoperable or unstable. The use of Group V elements as dopants for p-type semiconductor materials can be particularly difficult. Summary of the Invention [Problem to be solved by the invention]

[0003]

[0003] Therefore, there is a need for an alternative buffer layer for use with an absorber layer doped with a Group V p-type dopant. [Means for solving the problem]

[0004]

[0004] Embodiments provided herein relate to photovoltaic devices having buffer layers compatible with Group V dopants. These and additional features provided by the embodiments described herein will be more fully understood in view of the following detailed description, taken in conjunction with the drawings.

[0005]

[0005] The embodiments set forth in the drawings are illustrative and exemplary in nature and are not intended to limit the subject matter defined by the claims. The following detailed description of exemplary embodiments can be understood when read in conjunction with the following drawings, in which appropriate structure is indicated with appropriate reference numerals and in which: [Brief description of the drawings]

[0006] [Figure 1] 1 illustrates generally a cross-sectional view of a photovoltaic device according to one or more embodiments shown and described herein. [Diagram 2]

[0007] 1 illustrates a schematic representation of a substrate according to one or more embodiments shown and described herein. [Diagram 3]

[0008] 2 illustrates a schematic diagram of a buffer layer according to one or more embodiments shown and described herein. [Figure 4]

[0009] 2 illustrates a schematic diagram of a buffer layer according to one or more embodiments shown and described herein. [Diagram 5]

[0010] 1 illustrates a schematic diagram of a process for annealing a stack according to one or more embodiments shown and described herein. [Figure 6]

[0011] 1 shows a graph illustrating a normalized photoluminescence spectrum according to one or more embodiments shown and described herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007]

[0012] Embodiments of photovoltaic devices are provided having buffer layers that are compatible with Group V dopants.Various embodiments of photovoltaic devices and methods of forming photovoltaic devices are described in more detail herein.

[0008]

[0013] Referring now to FIG. 1, an embodiment of a photovoltaic device 100 is illustrated in schematic form. The photovoltaic device 100 may be configured to receive light and convert the light into an electrical signal, e.g., photons may be absorbed from the light and converted into an electrical signal via the photovoltaic effect. Accordingly, the photovoltaic device 100 may define an energy side 102 configured to be exposed to a light source, e.g., the sun. The photovoltaic device 100 may also define an opposite side 104 that is offset from the energy side 102, e.g., by multiple layers of material. It should be noted that the term "light" may refer to various wavelengths of the electromagnetic spectrum, such as, but not limited to, ultraviolet (UV), infrared (IR), and visible wavelengths of the electromagnetic spectrum. "Sunlight," as used herein, refers to light emitted from the sun. The photovoltaic device 100 may include multiple layers disposed between the energy side 102 and the opposite side 104. As used herein, the term "layer" refers to a thickness of material provided on a surface. Each layer may include the entire surface (i.e., a continuous layer) or any portion thereof (i.e., a discontinuous layer). For example, a continuous layer may be substantially uninterrupted, while a discontinuous layer may have one or more voids formed through the layer that are occupied by a different material.

[0009]

[0014] 1 and 2 collectively, the layers of the photovoltaic device 100 may include a substrate 110 configured to facilitate the transmission of light into the photovoltaic device 100. The substrate 110 may be disposed on the energy side 102 of the photovoltaic device 100. The substrate 110 may have a first surface 112 that substantially faces the energy side 102 of the photovoltaic device 100 and a second surface 114 that substantially faces the opposite side 104 of the photovoltaic device 100. One or more layers of material may be disposed between the first surface 112 and the second surface 114 of the substrate 110.

[0010]

[0015] The substrate 110 may include a transparent layer 120 having a first surface 122 that substantially faces the energy side 102 of the photovoltaic device 100 and a second surface 124 that substantially faces the opposite side 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 may include soda-lime glass or any glass with reduced iron content. The transparent layer 120 may have any suitable transmittance, including from about 250 nm to about 1300 nm in some embodiments, or from about 250 nm to about 950 nm in other embodiments. The transparent layer 120 may have any suitable transmittance, including, for example, greater than about 50% in one embodiment, greater than about 60% in another embodiment, greater than about 70% in yet another embodiment, greater than about 80% in a further embodiment, or greater than about 85% in yet another embodiment. In one embodiment, the transparent layer 120 may be formed from glass having a transmittance of about 90% or greater. 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 improve the durability of the substrate 110, and may include, for example, but is not limited to, an anti-reflective coating, an anti-soiling coating, or a combination thereof.

[0011]

[0016] 1 , the photovoltaic device 100 may include a buffer layer 130 configured to mitigate diffusion of contaminants (e.g., sodium) from the substrate 110 that may lead to degradation or delamination. The buffer layer 130 may have a first surface 132 that substantially faces the energy side 102 of the photovoltaic device 100 and a second surface 134 that substantially faces the opposite side 104 of the photovoltaic device 100. In some embodiments, the buffer layer 130 may be provided adjacent to the substrate 110. For example, the first surface 132 of the buffer layer 130 may be provided on the second surface 114 of the substrate 110. The phrase "adjacent to" as used herein means that two layers are disposed adjacent to each other with no intervening material between at least a portion of the layers.

[0012]

[0017] In general, the buffer layer 130 may be substantially transparent, thermally stable, have a reduced number of pinholes, have high sodium blocking capability, and have good adhesion properties. Alternatively or additionally, the buffer layer 130 may be configured to apply color suppression to the light. The buffer layer 130 may include one or more layers of suitable materials, including, but not limited to, tin oxide, silicon dioxide, aluminum doped silicon oxide, silicon oxide, silicon nitride, or aluminum oxide. The buffer layer 130 may have any suitable thickness bounded by the first surface 132 and the second surface 134, such as, 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]

[0018] 2, the photovoltaic device 100 may include a transparent conductive oxide (TCO) layer 140 configured to provide an electrical contact for transporting charge carriers generated by the photovoltaic device 100. The TCO layer 140 may have a first surface 142 that substantially faces the energy side 102 of the photovoltaic device 100 and a second surface 144 that substantially faces the opposite side 104 of the photovoltaic device 100. In some embodiments, the TCO layer 140 may be disposed adjacent to the buffer layer 130. For example, the first surface 142 of the TCO layer 140 may be disposed on the second surface 134 of the buffer layer 130. In general, the TCO layer 140 may be formed from one or more layers of a substantially transparent, wide bandgap n-type semiconductor material. In particular, the wide bandgap may have a large energy value compared to the photon energy of the light, reducing undesirable light absorbance. The TCO layer 140 may be made of, but is not limited to, tin oxide, fluorine doped tin oxide (e.g., F:SnO, F:SnO, or F:SnO x The insulating layer may comprise one or more layers of a suitable material including tin oxide, indium tin oxide, or cadmium stannate.

[0014]

[0019] The photovoltaic device 100 may include a buffer layer 150 configured to provide a low conductive layer between the TCO layer 140 and any adjacent semiconductor layers. The buffer layer 150 may have a first surface 152 that substantially faces the energy side 102 of the photovoltaic device 100 and a second surface 154 that substantially faces the opposite side 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 140 may include a material having a higher resistivity than the TCO layer 140, including, but not limited to, high purity tin oxide (SnO, SnO2 or SnO x ), magnesium oxide (MgO), magnesium zinc oxide (e.g., Zn 1-x Mg x O), silicon dioxide (SiO2), manganese oxide (MnO x ), silicon nitride (SiNx ) or any combination thereof. As used herein, manganese oxide (MnO x ) includes compounds of manganese and oxygen, where manganese is present in any suitable oxidation state. In some embodiments, MnO x The x in the formula (I) may be about 1 or more, for example, but not limited to, about 1 or more and about 2 or less. Accordingly, the exemplary MnO x The compounds include, but are not limited to, MnO (corresponding to x=1), MnO2 (corresponding to x=2), Mn2O3 (corresponding to x=1.5), or Mn3O4 (corresponding to x=1.3). Exemplary MnO x The compounds may exist as a single phase or as a multiphase mixture, which may or may not contain some Mn and O amorphous components, respectively.

[0015]

[0020] In some embodiments, the material of the buffer layer 140 may be configured to substantially match the band gap of an adjacent semiconductor layer (e.g., absorber). The buffer layer 150 may have a thickness 156 between the first surface 152 and the second surface 154. The thickness 156 may range any suitable distance, for example, greater than about 0.5 nanometers (nm) in one embodiment, between about 1 nm and about 200 nm in another embodiment, between about 1 nm and about 100 nm in another embodiment, or between about 1 nm and about 10 nm in a further embodiment, or between about 1 nm and about 3 nm in yet another embodiment. In some embodiments, the buffer layer 150 or layers thereof may be discontinuous. For example, the buffer layer 150 may be a substantially discontinuous MnO x The layer may include a layer of MnO x When the layers are discontinuous, MnO x The layer can be characterized using inductively coupled plasma optical emission spectroscopy (ICP-OES). x The layer has a density of at least about 0.05 μg / cm 2 , for example, about 0.05 μg / cm in one embodiment 2 More than or equal to 15μg / cm 2 In another embodiment, about 0.1 μg / cm2 or more and approximately 12 μg / cm 2 or less, or in further embodiments, about 0.2 μg / cm 2 More than 6μg / cm 2 The Mn content may be as follows:

[0016]

[0021] 1 and 3 collectively, the buffer layer 150 may include a plurality of layers 200. In particular, the plurality of layers 200 of the buffer layer 150 may include a base layer 210 disposed on a first surface 152 of the buffer layer 150. Accordingly, the base layer 210 may be disposed adjacent to the TCO layer 140. In some embodiments, the first surface 152 of the buffer layer 150 may be a surface of the base layer 210. The base layer 210 may have a second surface 214 that substantially faces the opposite side 104 of the photovoltaic device 100. The base layer 210 may have a thickness 216 between the first surface 152 and the second surface 214. In some embodiments, the thickness 216 of the base layer 210 may span a majority of the thickness 156 of the buffer layer 150.

[0017]

[0022] The plurality of layers 200 of the buffer layer 150 may include an interface layer 220 disposed on the second surface 154 of the buffer layer 150. In general, the interface layer 220 may be located further from the energy side 102 of the photovoltaic device than the base layer 210. The interface layer 220 may have a first surface 224 that substantially faces the energy side 102 of the photovoltaic device 100. In some embodiments, the second surface 154 of the buffer layer 150 may be a surface of the interface layer 220. The interface layer 220 may have a thickness 226 between the first surface 222 and the second surface 154. In some embodiments, the thickness 226 of the interface layer 220 may be less than the thickness 216 of the base layer 210.

[0018]

[0023] According to embodiments provided herein, the base layer 210 and the interface layer 220 may be composed of different materials. For example, in some embodiments, the base layer 210 is made of tin oxide (SnO, SnO2, or SnO x), and the interface layer 220 may include magnesium oxide (MgO, magnesium zinc oxide (e.g., Zn 1-x Mg x O), silicon dioxide (SiO2), manganese oxide (MnO x ), and silicon nitride (SiN x ) may be included.

[0019]

[0024] 1 and 4 collectively, the layers 200 of the buffer layer 150 may include one or more intermediate layers 230 disposed between the base layer 210 and the interface layer 220. The one or more intermediate layers 230 may have a first surface 232 substantially facing the energy side 102 of the photovoltaic device 100 and a second surface 234 substantially facing the opposite side 104 of the photovoltaic device 100. The one or more intermediate layers 230 may be provided adjacent to the base layer 210 and the interface layer 220. Accordingly, the first surface 232 of the one or more intermediate layers 230 may be provided on the second surface 214 of the base layer 210, and the second surface 234 of the one or more intermediate layers 230 may be provided on the first surface 224 of the interface layer 210. The one or more intermediate layers 230 may have a thickness 236 between the first surface 232 and the second surface 234. In some embodiments, the thickness 236 of the one or more intermediate layers 230 may be less than the thickness 216 of the base layer 210 .

[0020]

[0025] According to embodiments of the present disclosure, the one or more intermediate layers 230 may be composed of a material different from the base layer 210 and the interface layer 220. For example, in some embodiments, the one or more intermediate layers 230 may be composed of a material different from that of ... zinc magnesium oxide (e.g., Zn 1-x Mg x O).

[0021]

[0026] Referring again to FIG. 1 , the photovoltaic device 100 may include an absorbing layer 160 configured to cooperate with another layer to form a pn junction in the photovoltaic device 100. Accordingly, absorbing photons of light can free electron-hole pairs and generate carrier flow, thereby obtaining electrical power. The absorbing layer 160 may have a first surface 162 that substantially faces the energy side 102 of the photovoltaic device 100 and a second surface 164 that substantially faces the opposite side 104 of the photovoltaic device 100. A thickness of the absorbing layer 160 may be defined between the first surface 162 and the second surface 164. The thickness of the absorbing layer 160 may be between about 0.5 μm and about 10 μm, such as between about 1 μm and about 7 μm in one embodiment, or between about 1.5 μm and about 4 μm in another embodiment.

[0022]

[0027] According to embodiments described herein, the absorbing layer 160 may be formed from a p-type semiconductor material having an excess of positive charge carriers, i.e., holes or acceptors. The absorbing layer 160 may include any suitable p-type semiconductor material, such as a II-VI semiconductor. Specific examples include, but are not limited to, semiconductor materials including cadmium, tellurium, selenium, or any combination thereof. Suitable examples include, but are not limited to, ternary materials of cadmium, selenium, and tellurium (e.g., CdSe x Te 1-x ), or compounds containing cadmium, selenium, tellurium, and one or more additional elements.

[0023]

[0028] In embodiments in which the absorbing layer 160 includes tellurium and cadmium, the atomic percentage of tellurium may be greater than or equal to about 25 atomic percent and less than or equal to about 50 atomic percent, such as greater than about 30 atomic percent and less than about 50 atomic percent in one embodiment, greater than about 40 atomic percent and less than about 50 atomic percent in a further embodiment, or greater than about 47 atomic percent and less than about 50 atomic percent in yet another embodiment, etc. Alternatively or additionally, the atomic percentage of tellurium in the absorbing layer 160 may be greater than about 45 atomic percent, such as greater than about 49% in one embodiment. It should be noted that the atomic percentages described herein represent the absorbing layer 160 as a whole, and that the atomic percentage of material at a particular location in the absorbing layer 160 may vary depending on the thickness compared to the overall composition of the absorbing layer 160.

[0024]

[0029] In embodiments in which absorbing layer 160 includes selenium and tellurium, the atomic percent of selenium in absorbing layer 160 may be greater than about 0 atomic percent and less than or equal to about 25 atomic percent, such as greater than about 1 atomic percent and less than about 20 atomic percent in one embodiment, greater than about 1 atomic percent and less than about 15 atomic percent in another embodiment, or greater than about 1 atomic percent and less than about 8 atomic percent in a further embodiment, etc. It should be noted that the concentration of tellurium, selenium, or both may vary with the thickness of absorbing layer 160. For example, absorbing layer 160 may be a compound including a mole fraction x of selenium and a mole fraction 1-x of tellurium (Se x Te 1-x ), x can vary within the absorbing layer 160 with distance from the first surface 162 of the absorbing layer 160.

[0025]

[0030] 1, the absorbing layer 160 may be doped with a dopant configured to manipulate the concentration of charge carriers. In some embodiments, the absorbing layer 160 may be doped with a Group I or Group V dopant, such as copper, arsenic, phosphorous, antimony, or combinations thereof. The total concentration of dopants in the absorbing layer 160 may be controllable. In some embodiments, the absorbing layer 160 may be doped with at least about 1×10 atoms. 16 pieces / cm3 , for example, in one embodiment, at least about 5×10 atoms 16 pieces / cm 3 and in another embodiment about 9×10 atoms 16 pieces / cm 3 from about 7 x 10 atoms 18 pieces / cm 3 or in a further embodiment between about 1×10 atoms 17 pieces / cm 3 from about 4 × 10 atoms 18 pieces / cm 3 Alternatively or additionally, in some embodiments, the peak concentration of the group V dopant in absorbing layer 160 may be at least about 1×10 atoms. 16 pieces / cm 3 Alternatively or in addition, the amount of dopant may vary with distance from the first surface 162 of the absorbing layer 160.

[0026]

[0031] According to embodiments provided herein, a p-n junction may be formed by providing an absorbing layer 160 sufficiently proximate to a portion of the photovoltaic device 100 having an excess of negative charge carriers, i.e., electrons or donors. In some embodiments, the absorbing layer 160 may be provided adjacent to an n-type semiconductor material. Alternatively, one or more intervening layers may be provided between the absorbing layer 160 and the n-type semiconductor material. In some embodiments, the absorbing layer 160 may be provided adjacent to the buffer layer 150. For example, the first surface 162 of the absorbing layer 160 may be provided on the second surface 154 of the buffer layer 150.

[0027]

[0032] The photovoltaic device 100 may include a back contact layer 180 configured to mitigate unwanted alterations of dopants and provide electrical contact to the absorbing layer 160. The back contact layer 180 may have a first surface 182 substantially facing the energy side 102 of the photovoltaic device 100 and a second surface 184 substantially facing the opposite side 104 of the photovoltaic device 100. A thickness of the back contact layer 180 may be defined between the first surface 182 and the second surface 184. The thickness of the back contact layer 180 may be between about 5 nm and about 200 nm, such as between about 10 nm and about 50 nm in one embodiment.

[0028]

[0033] In some embodiments, the back contact layer 180 may be disposed adjacent to the absorbing layer 160. For example, a first surface 182 of the back contact layer 180 may be disposed on the second surface 164 of the absorbing layer 160. In some embodiments, the back contact layer 180 may include one or more layers containing binary or ternary combinations of Group I, II, VI materials, such as zinc, copper, cadmium, and tellurium in various compositions. Further exemplary materials include, but are not limited to, zinc telluride doped with copper telluride, or zinc telluride alloyed with copper telluride.

[0029]

[0034] The photovoltaic device 100 may include a conductive layer 190 configured to provide electrical contact with the absorbing layer 160. The conductive layer 190 may have a first surface 192 that substantially faces the energy side 102 of the photovoltaic device 100 and a second surface 194 that substantially faces the opposite side 104 of the photovoltaic device 100. In some embodiments, the conductive layer 190 may be provided adjacent to the back contact layer 180. For example, the first surface 192 of the conductive layer 190 may be provided on the second surface 184 of the back contact layer 180. The conductive layer 190 may include one or more layers of any suitable conductive material, such as a nitrogen-containing metal, silver, nickel, copper, aluminum, titanium, palladium, chromium, molybdenum, gold, or the like. Suitable examples of nitrogen-containing metal layers may include aluminum nitride, nickel nitride, titanium nitride, tungsten nitride, selenium nitride, tantalum nitride, or vanadium nitride.

[0030]

[0035] The photovoltaic device 100 may include a back support 196 configured to cooperate with the substrate 110 to form a housing for the photovoltaic device 100. The back support 196 may be disposed on the opposite side 102 of the photovoltaic device 100. For example, the back support 196 may be formed adjacent to the conductive layer 190. The back support 196 may include any suitable material, such as, for example, glass (e.g., soda-lime glass).

[0031]

[0036] 1 and 5 collectively, the fabrication of the photovoltaic device 100 generally involves sequentially depositing functional layer precursors in a “stack” of layers by one or more thin film deposition techniques, including, but not limited to, sputtering, spraying, evaporation, molecular beam deposition, pyrolysis, close-spaced sublimation (CSS), pulsed laser deposition (PLD), chemical vapor deposition (CVD), electrochemical deposition (ECD), atomic layer deposition (ALD), or vapor transport deposition (VTD). In some embodiments, the partially formed photovoltaic device 240 can be subjected to an annealing step to improve the functionality of the absorber layer 160. For example, the partially formed photovoltaic device 240 can include the absorber layer 160 adjacent to the stack 204. The stack 204 can include one or more layers of the photovoltaic device 100 disposed between the absorber layer 160 and the energy side 102.

[0032]

[0037] The partially formed photovoltaic device 240 is exposed to a reduced ambient environment 246, i.e., an environment having less than 500 parts per million (ppm) oxygen. The absorber layer 160 may be annealed in a process chamber 244 that includes a glass substrate 246. During the annealing process, the absorber layer 160 may be contacted with an annealing compound 248 that includes cadmium chloride (CdCl2). Generally, the annealing process involves heating the absorber layer 160 (e.g., a polycrystalline semiconductor material) for a time and at a temperature sufficient to promote recrystallization of the absorber layer 160. In addition, the heat, reducing ambient environment 246, and annealing compound 248 may cooperate to promote grain growth and activation of Group V dopants, such as nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), or combinations thereof, in the absorber layer 160. In some embodiments, the compounds in the buffer layer 150 (e.g., MnO x The oxidation state of MnO can change during the annealing process. x can be present, for example, as MnO2 (corresponding to x=2), Mn3O4 (corresponding to x=1.3), or a combination thereof. Alternatively or additionally, prior to annealing, MnO xmay contain amorphous components of Mn and O. After annealing, at least a portion of MnO x can change its oxidation state, which leads to different MnO x This can be evidenced by the presence of a compound.

[0033]

[0038] In some cases, buffer layer 150 may also be doped with a group V dopant. For example, the group V dopant may be diffused into buffer layer 150. Accordingly, in some embodiments, the peak concentration of group V dopant in buffer layer 150 is at least about 1×10 atoms. 16 pieces / cm 3 Therefore, MnO x The layers may include a Group V dopant. In alternative embodiments, one or more of the layers of the buffer layer 150 may be free of a Group V dopant, i.e., diffusion may be reduced.

[0034]

[0039] The interface region 158 may include an interface between the first surface 162 of the absorbing layer 160 and the second surface 154 of the buffer layer 150. For example, the interface region 158 may start at the first surface 152 of the buffer layer 150 and extend to the absorbing layer 160. The interface region 158 may have a thickness of about 500 nm or less, such as, for example, between about 0.5 nm and 500 nm in one embodiment, or between about 1 nm and 100 nm in another embodiment. Applicants have discovered that the buffer layer 150 performs in an unexpected manner when subjected to an annealing process. Without being bound by theory, it is believed that the chemical nature of the buffer layer 150 and the absorbing layer 160 may result in undesirable defects in the interface region 158. Many chemical compositions may be more susceptible to defects, such as during dopant activation in a reducing ambient environment 246. Such defects may reduce the efficiency of the photovoltaic device 100.

[0035]

[0040] The efficiency of the photovoltaic device 100 is affected by the MnO x For example, an MnO layer adjacent to the first surface 162 of the absorbing layer 160 may be included. x layer or MnO sufficiently close to the first surface 162 of the absorbing layer 160.x That is, one or more of the layers 200 of the buffer layer is made of MnO x layer and the first surface 162 of the absorbing layer 160. Accordingly, the MnO x The layer may be within about 200 nm of the first surface 162 of the absorbing layer 160, such as less than about 100 nm in one embodiment, less than about 80 nm in another embodiment, less than about 35 nm in yet another embodiment, less than about 15 nm in a further embodiment, etc.

[0036]

[0041] EXAMPLES

[0037]

[0042] Comparative Example: A laminated film was prepared on a glass substrate. The stack included a TCO layer of fluorine-doped tin oxide, a buffer layer of tin oxide formed on the TCO layer, and an absorber layer of As:CdSeTe. The stack was annealed with an annealing compound containing cadmium chloride (CdCl2) in a reducing ambient environment.

[0038]

[0043] Example 1 was formed in the same manner as in the comparative example, but the buffer layer was formed of a tin oxide base layer and Zn 1-x Mg x Example 2 was formed in the same manner as the comparative example, but the buffer layer was modified to have a tin oxide base layer and a SiO2 interface layer. Example 3 was formed in the same manner as the comparative example, but the buffer layer was modified to have a tin oxide base layer, a Zn 1-x Mg x Example 4 was prepared in the same manner as the comparative example, but the buffer layer was modified to have a base layer of tin oxide and an intermediate layer of MnO x The buffer layer was modified to have an interface layer of Zn. 1-x Mg x The SiO2 substrate was modified to have a base layer of O and an interfacial layer of SiO2. Several comparative and example samples were prepared and characterized using secondary ion mass spectrometry (SIMS).

[0039]

[0044]

[0040] [Table 1]

[0041]

[0045] 1 and 6 collectively, photoluminescence spectroscopy was used to characterize the recombination at the buffer and absorber layer interfaces of the comparative example and Examples 1-4. In general, higher intensity of luminescence in response to light injected into the energy side 102 (FIG. 1) may correspond to less carrier recombination at the buffer and absorber layer interfaces. Thus, higher intensity may correspond to higher efficiency of the photovoltaic device 100.

[0042]

[0046] The photoluminescence intensity (PLI) of the comparative example and examples 1-4 is shown in FIG. 6. In particular, PLI spectrum 250 corresponds to the comparative example, PLI spectrum 252 corresponds to example 1, PLI spectrum 254 corresponds to example 2, PLI spectrum 256 corresponds to example 3, and PLI spectrum 258 corresponds to example 4. Spectra 250, 252, 254, 256, 258 are each normalized to the peak value of PLI spectrum 250. PLI spectrum 252, PLI spectrum 254, PLI spectrum 256, and PLI spectrum 258 demonstrate the improved performance of examples 1-4 over the comparative example. In particular, PLI spectrum 252 corresponds to about a 700% peak intensity improvement of example 1 over the comparative example. PLI spectrum 254 corresponds to about a 1000% peak intensity improvement of example 2 over the comparative example. PLI spectra 256 and 258 correspond to about a 1500% peak intensity improvement of examples 3 and 4 over the comparative example. Further testing demonstrated an improvement in performance for Example 5 similar to that shown for Example 3.

[0043]

[0047] Various examples of Example 4 were analyzed using X-ray diffraction (XRD) to determine the effect of the annealing process. The composition of the buffer layer 150 before and after the annealing step was determined. In one example, the buffer layer 150 included Mn3O4 before the annealing step and included MnO and Mn3O4 after the annealing step. In another example, the buffer layer 150 included Mn2O3 before the annealing step and included Mn3O4 after the annealing step. In a further example, the buffer layer 150 included MnO2 and Mn3O4 before the annealing step and included Mn3O4 (but not MnO2) after the annealing step. In another further example, the buffer layer 150 included MnO2 before the annealing step and included MnO2 and Mn3O4 after the annealing step.

[0044]

[0048] According to embodiments provided herein, the photovoltaic device may include an absorber layer disposed on the buffer layer. The absorber layer may have a first surface and a second surface. The absorber layer may include cadmium and tellurium. The absorber layer may be doped with a group V dopant. The buffer layer may be MnO x The substrate may include a layer.

[0045]

[0049] According to embodiments provided herein, a method of annealing a partially formed photovoltaic device may include contacting an absorber layer with an annealing compound comprising cadmium chloride. The partially formed photovoltaic device may include an absorber layer disposed on a buffer layer. The absorber layer may include cadmium and tellurium. The buffer layer may include MnO x The method may include heating the absorbing layer for a time and at a temperature sufficient to promote recrystallization of the absorbing layer. The method may include diffusing a group V dopant through the absorbing layer and into the buffer layer.

[0046]

[0050] The terms "substantially" and "about" may be used herein to express the inherent degree of uncertainty that may result from any quantitative comparison, value, measurement, or other representation. These terms are also used to express the degree to which a quantitative expression can vary from its stated reference without changing the basic functionality of the subject matter at issue.

[0047]

[0051] While particular embodiments have been illustrated and described herein, it should be understood that various other changes and modifications can be made without departing from the spirit and scope of the claimed subject matter. Moreover, although various aspects of the claimed subject matter have been described herein, such aspects need not be utilized in combination. It is therefore intended that the appended claims encompass all such changes and modifications that are within the scope of the claimed subject matter. [Mode of the invention] [1] 1. A photovoltaic device comprising an absorber layer disposed on a buffer layer, the absorbent layer having a first surface and a second surface; the absorbing layer comprises cadmium and tellurium; the absorbing layer is doped with a Group V dopant; The buffer layer is made of MnO x A photovoltaic device comprising a layer. [2] The MnO x The photovoltaic device of claim 1 , wherein a layer is adjacent the first surface of the absorbing layer. [3] The MnO x The photovoltaic device of claim 1 , wherein the layer has a thickness between 1 nm and 3 nm. [4] The peak concentration of the Group V dopant in the absorbing layer is at least 1×10 atoms 16 pieces / cm 3 2. The photovoltaic device of claim 1 , wherein: [5] the buffer layer having a first surface and a second surface adjacent to the absorbent layer; the buffer layer includes a base layer disposed on the first surface of the buffer layer and an interface layer disposed on the second surface of the buffer layer; the base layer of the buffer layer comprises tin oxide; The photovoltaic device of claim 1 , wherein the interface layer of the buffer layer is composed of a different material than the base layer of the buffer layer. [6] The photovoltaic device of claim 5 , wherein the interfacial layer of the buffer layer comprises magnesium oxide. [7] The photovoltaic device of claim 5 , wherein the interfacial layer of the buffer layer comprises magnesium zinc oxide. [8] The photovoltaic device of claim 5 , wherein the interfacial layer of the buffer layer comprises silicon dioxide. [9] The interface layer of the buffer layer is x The photovoltaic device of claim 5 which is a layer.

[10] The photovoltaic device of claim 5 , wherein the interfacial layer of the buffer layer comprises silicon nitride.

[11] The photovoltaic device of claim 5 , wherein the base layer of the buffer layer is thicker than the interface layer of the buffer layer.

[12] the buffer layer includes an intermediate layer disposed between the base layer of the buffer layer and the interface layer of the buffer layer; the intermediate layer of the buffer layer is composed of a material different from the base layer of the buffer layer and the interface layer of the buffer layer; 6. The photovoltaic device of claim 5.

[13] The photovoltaic device of claim 12 , wherein the base layer of the buffer layer is thicker than the intermediate layer of the buffer layer.

[14] The photovoltaic device of claim 12 , wherein the intermediate layer of the buffer layer comprises magnesium zinc oxide.

[15] 15. The photovoltaic device of claim 14, wherein the interfacial layer of the buffer layer comprises silicon dioxide.

[16] The MnO x 10. The photovoltaic device of claim 1, wherein a layer is within 200 nm of the first surface of the absorbing layer.

[17] The MnO x The photovoltaic device of claim 1 , wherein the layer is discontinuous.

[18] The MnO xThe layer is at least 0.05 μg / cm 2 20. The photovoltaic device of claim 17 having a Mn content of

[19] The MnO x 10. The photovoltaic device of claim 1, wherein the layer comprises MnO2.

[20] The MnO x 10. The photovoltaic device of claim 1, wherein the layer comprises Mn2O3. [twenty one] The MnO x 10. The photovoltaic device of claim 1, wherein the layer comprises Mn3O4. [twenty two] The MnO x The photovoltaic device of claim 1 , wherein the layer has a thickness between 1 nm and 10 nm. [twenty three] The MnO x 10. The photovoltaic device of claim 1, wherein x in the layer is 1 or greater and 2 or less. [twenty four] The photovoltaic device of claim 1 , wherein the buffer layer is disposed adjacent to a transparent conductive oxide layer. [twenty five] The transparent conductive oxide layer contains cadmium stannate, and the MnO x The photovoltaic device of claim 24 , wherein a layer is adjacent to the absorbing layer.

[26] The transparent conductive oxide layer comprises fluorine-doped tin oxide, and the MnO x The photovoltaic device of claim 24 , wherein a layer is adjacent to the absorbing layer.

[27] the transparent conductive oxide layer comprises fluorine-doped tin oxide; the buffer layer having a first surface and a second surface adjacent to the absorbent layer; the buffer layer includes a base layer disposed on the first surface of the buffer layer and an interface layer disposed on the second surface of the buffer layer; the base layer of the buffer layer comprises tin oxide; The interface layer of the buffer layer is x The layer is 25. The photovoltaic device of claim 24.

[28] the transparent conductive oxide layer comprises fluorine-doped tin oxide; the buffer layer having a first surface and a second surface adjacent to the absorbent layer; the buffer layer includes a base layer disposed on the first surface of the buffer layer and an interface layer disposed on the second surface of the buffer layer; the buffer layer includes an intermediate layer disposed between the base layer of the buffer layer and the interface layer of the buffer layer; the base layer of the buffer layer comprises tin oxide; The intermediate layer of the buffer layer is MnO x layer, the interface layer of the buffer layer comprises silicon dioxide; 25. The photovoltaic device of claim 24.

[29] The transparent conductive oxide layer comprises indium tin oxide, and the MnO x The photovoltaic device of claim 24 , wherein a layer is adjacent to the absorbing layer.

[30] the buffer layer having a first surface and a second surface adjacent to the absorbent layer; the buffer layer includes a base layer disposed on the first surface of the buffer layer; The base layer comprises magnesium zinc oxide. 30. The photovoltaic device of claim 29.

[31] 1. A method of annealing a partially formed photovoltaic device, the partially formed photovoltaic device comprising an absorber layer disposed on a buffer layer, the absorber layer comprising cadmium and tellurium, the buffer layer comprising MnO x layer, said method comprising: contacting the absorbing layer with an annealing compound comprising cadmium chloride; heating the absorbing layer for a time and at a temperature sufficient to promote recrystallization of the absorbing layer; diffusing a group V dopant through the absorbing layer and into the buffer layer; A method comprising:

[32] The MnO x The method of claim 31 , comprising changing the oxidation state of the layer.

[33] The MnO x 33. The photovoltaic device or method of any one of claims 1 and 31-32, wherein a layer is adjacent the first surface of the absorber layer.

[34] The MnO x 34. The photovoltaic device or method of any one of claims 1 and 31 to 33, wherein the layer has a thickness between 1 nm and 3 nm.

[35] The peak concentration of the Group V dopant in the absorbing layer is at least 1×10 atoms 16 pieces / cm 3 35. The photovoltaic device or method of claim 1, wherein

[36] the buffer layer having a first surface and a second surface adjacent to the absorbent layer; the buffer layer includes a base layer disposed on the first surface of the buffer layer and an interface layer disposed on the second surface of the buffer layer; the base layer of the buffer layer comprises tin oxide; the interface layer of the buffer layer is composed of a material different from the base layer of the buffer layer; 36. A photovoltaic device or method according to any one of claims 1 and 31 to 35.

[37] 37. The photovoltaic device or method of claim 36, wherein the interfacial layer of the buffer layer comprises magnesium oxide.

[38] 37. The photovoltaic device or method of claim 36, wherein the interfacial layer of the buffer layer comprises magnesium zinc oxide.

[39] 37. The photovoltaic device or method of claim 36, wherein the interfacial layer of the buffer layer comprises silicon dioxide.

[40] The interface layer of the buffer layer is x 37. The photovoltaic device or method of claim 36, which is a layer.

[41] 37. The photovoltaic device of claim 36, wherein the interfacial layer of the buffer layer comprises silicon nitride. method.

[42] 37. The photovoltaic device or method of claim 36, wherein the base layer of the buffer layer is thicker than the interface layer of the buffer layer.

[43] an intermediate layer disposed between the base layer of the buffer layer and the interface layer of the buffer layer; the intermediate layer of the buffer layer is composed of a material different from the base layer of the buffer layer and the interface layer of the buffer layer; 43. A photovoltaic device or method according to any one of claims 36 to 42.

[44] 44. The photovoltaic device or method of claim 43, wherein the base layer of the buffer layer is thicker than the intermediate layer of the buffer layer.

[45] 45. The photovoltaic device or method of claim 43 or 44, wherein the intermediate layer of the buffer layer comprises magnesium zinc oxide.

[46] The MnO x 46. ​​The photovoltaic device or method of any one of claims 1 and 31-45, wherein a layer is within 200 nm of the first surface of the absorbing layer.

[47] The MnO x 47. The photovoltaic device or method of any one of claims 1 and 31-46, wherein the layer is discontinuous.

[48] The MnO x The layer is at least 0.05 μg / cm 2 48. The photovoltaic device or method of any one of claims 1 and 31 to 47, having a Mn content of

[49] The MnO x 49. The photovoltaic device or method of any one of claims 1 and 31-48, wherein the layer comprises MnO.

[50] The MnO x49. The photovoltaic device or method of any one of claims 1 and 31-48, wherein the layer comprises MnO2.

[51] The MnO x 49. The photovoltaic device or method of any one of claims 1 and 31-48, wherein the layer comprises Mn2O3.

[52] The MnO x 49. The photovoltaic device or method of any one of claims 1 and 31-48, wherein the layer comprises Mn3O4.

[53] 53. The photovoltaic device or method of any one of claims 1 and 31-52, wherein the absorbing layer comprises selenium.

[54] The MnO x 54. The photovoltaic device or method of any one of claims 1, 31-33 and 35-53, wherein the layer has a thickness between 1 nm and 10 nm.

[55] The MnO x 55. The photovoltaic device or method of any one of claims 1, 31-48 and 53-54, wherein x in the layer is 1 or greater and 2 or less.

[56] 56. The photovoltaic device or method of any one of claims 1, 31-35 and 46-55, wherein the buffer layer is provided adjacent to a transparent conductive oxide layer.

[57] The transparent conductive oxide layer contains cadmium stannate, and the MnO x A layer is adjacent to the absorbent layer. 57. The photovoltaic device or method of claim 56, wherein

[58] The transparent conductive oxide layer comprises fluorine-doped tin oxide, and the MnO x 57. The photovoltaic device or method of claim 56, wherein a layer is adjacent to the absorbing layer.

[59] the transparent conductive oxide layer comprises fluorine-doped tin oxide; the buffer layer having a first surface and a second surface adjacent to the absorbent layer; the buffer layer includes a base layer disposed on the first surface of the buffer layer and an interface layer disposed on the second surface of the buffer layer; the base layer of the buffer layer comprises tin oxide; The interface layer of the buffer layer is x The layer is 57. The photovoltaic device or method of claim 56.

[60] the transparent conductive oxide layer comprises fluorine-doped tin oxide; the buffer layer having a first surface and a second surface adjacent to the absorbent layer; the buffer layer includes a base layer disposed on the first surface of the buffer layer and an interface layer disposed on the second surface of the buffer layer; the buffer layer includes an intermediate layer disposed between the base layer of the buffer layer and the interface layer of the buffer layer; the base layer of the buffer layer comprises tin oxide; The intermediate layer of the buffer layer is x layer, the interface layer of the buffer layer comprises silicon dioxide; 57. The photovoltaic device or method of claim 56.

[61] The transparent conductive oxide layer comprises fluorine-doped tin oxide, and the MnO x 57. The photovoltaic device or method of claim 56, wherein a layer is adjacent to the absorbing layer.

[62] the transparent conductive oxide layer comprises fluorine-doped tin oxide; the buffer layer having a first surface and a second surface adjacent to the absorbent layer; the buffer layer includes a base layer disposed on the first surface of the buffer layer and an interface layer disposed on the second surface of the buffer layer; the base layer of the buffer layer comprises tin oxide; The interface layer of the buffer layer is x The layer is 57. The photovoltaic device or method of claim 56.

[63] The transparent conductive oxide layer comprises indium tin oxide, and the MnO x 57. The photovoltaic device or method of claim 56, wherein a layer is adjacent to the absorbing layer.

[64] the buffer layer having a first surface and a second surface adjacent to the absorbent layer; the buffer layer includes a base layer disposed on the first surface of the buffer layer; the base layer comprises magnesium zinc oxide; 64. The photovoltaic device or method of claim 63.

[65] The MnO x 65. The photovoltaic device or method of any one of claims 1 and 31-64, wherein the layer comprises a Group V dopant.

Claims

1. 1. A method of annealing a film stack for a photovoltaic device, the film stack comprising an absorber layer disposed on a buffer layer, the absorber layer comprising cadmium and tellurium, the buffer layer comprising MnO ｘ layer, said method comprising: contacting the absorbing layer with an annealing compound comprising cadmium chloride; heating the absorbing layer to promote recrystallization of the absorbing layer; diffusing a Group V dopant through the absorbing layer and into the buffer layer; Including, The MnO ｘ The layer is at least 0.05 μg / cm ２ 15 μg / cm ２ The following Mn content: the buffer layer having a first surface and a second surface adjacent the absorbent layer; the buffer layer includes a base layer disposed on the first surface of the buffer layer and an interface layer disposed on the second surface of the buffer layer; the base layer of the buffer layer comprises tin oxide; and the interface layer of the buffer layer comprises silicon nitride; method.

2. The MnO ｘ The method of claim 1 including the step of altering the oxidation state of the layer.

3. The MnO ｘ The method of claim 1 or 2, wherein a layer is adjacent a first surface of the absorbent layer facing the buffer layer.

4. The MnO ｘ The method according to any one of claims 1 to 3, wherein the layer has a thickness between 1 nm and 3 nm.

5. The peak concentration of the Group V dopant in the absorbing layer is at least 1×10 atoms １６ pieces / cm ３ The method according to any one of claims 1 to 4, wherein

6. The method of claim 1 , wherein the interfacial layer of the buffer layer comprises at least one of magnesium oxide, silicon dioxide, or magnesium zinc oxide.

7. The interface layer of the buffer layer is ｘ The method of claim 1 , wherein the layer is a layer.

8. The method of claim 1 , wherein the base layer of the buffer layer is thicker than the interface layer of the buffer layer.

9. an intermediate layer disposed between the base layer of the buffer layer and the interface layer of the buffer layer; the intermediate layer of the buffer layer is composed of a material different from the base layer of the buffer layer and the interface layer of the buffer layer; The method according to claim 1, 6, 7 or 8.

10. The method of claim 9 , wherein the base layer of the buffer layer is thicker than the middle layer of the buffer layer.

11. 11. The method of claim 9 or 10, wherein the intermediate layer of the buffer layer comprises magnesium zinc oxide.

12. The MnO ｘ The method of any one of claims 1 to 11, wherein a layer is within 200 nm of the first surface of the absorbing layer that faces the buffer layer.

13. The MnO ｘ The method of any one of claims 1 to 12, wherein the layer has one or more voids formed through the MnO x layer.

14. The MnO ｘ The layer is MnO ２ The method according to any one of claims 1 to 13, comprising:

15. The MnO ｘ The layer is Mn ２ O ３ The method according to any one of claims 1 to 13, comprising:

16. The MnO ｘ The layer is Mn ３ O ４ The method according to any one of claims 1 to 13, comprising:

17. The MnO ｘ The method of any one of claims 1 to 13, wherein x in the layer is 1 or more and 2 or less.

18. The MnO ｘ The method of any one of claims 1 to 17, wherein the layer comprises a Group V dopant.

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