TW201212247A - Multi-junction photovoltaic cell devices - Google Patents

Abstract

III-V compound multi-junction photovoltaic cell devices are presented. The multi-junction photovoltaic device includes a germanium substrate with a shallow junction thereon. The shallow junction is sandwiched between a p-type doped germanium substrate and a phosphorous-containing n-type shallow diffusion region. A dual-junction cell structure with multiple stacked phosphide layers is disposed on the germanium substrate. A superlattice structure is interposed between the dual-junction cell structure and the germanium substrate.

Description

201212247 VI. Description of the Invention: [Technical Field] The present invention relates to a multi-junction photocell element, and more particularly to a ΙΠ-V-group multi-junction solar cell having a superlattice structure. [Prior Art] Solar cells are the key components for converting solar energy into electrical energy. Currently, the developed solar cell technologies include: smcon based solar ee 矽, 矽 thin film solar power; ^ (SiHC〇 n tMn film 8〇1 order CeH), dye-sensitized solar cell (d% sensitized solar cell), copper indium is more than rjIL, wide τ _ 卜; 』 In 蜂 码 』 』 』 』 』 』 』 』 』 』 』 』 』 』 』 』 』 』 』 』 』 』 』 』 囚 囚 囚 囚 囚 囚 囚 囚 囚 囚 囚 囚 囚 囚-V family sun +, L /

Concentrat b b battery (concentrator V-V compound solar cell), etc. °

The conventional III-V multi-junction solar cell (III-V ΓΐίΠ, Cell) refers to an element having a photoelectric effect by combining the m-th group of ν 兀 elements in the periodic table.

a = potential for grouping. Typical of this v-type multi-junction solar cell, the field of application / which is the most widely used, such as GalnP / GaAs / Ge and alnP / GaAs, is applied to the tandem type of gallium (GaAS). Furthermore, the use of ϊιι ν multi-junction solar power is mainly due to the fact that wafers capable of absorbing different wavelengths (10) are stacked due to: sunlight in the same wavelength range, making full use of the efficiency of y 0 1 . Furthermore, due to the absorption of solar energy, the photoelectric conversion rate is higher than that of the general 矽-based solar power=f: 匕 匕 匕 - - - - - - - - ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ The battery's power rotation will be changed by the intensity of the light' 201212247 The power output will increase as the intensity of the illumination increases. Therefore, if the solar cell component absorbs the solar spectrum more effectively, it will greatly increase the energy of the component. Conversion efficiency.

A multi-junction solar cell that improves light absorption efficiency is disclosed in U.S. Patent No. 7,339,109. By setting an InGaP layer as the pregnancy layer between the germanium substrate and the double junction epitaxial stack, the deposition temperature of the upper phosphorus-containing compound semiconductor is lowered to control the diffusion depth of the n-type dopant in the germanium substrate. The InGaP • layer can also serve as a diffusion barrier layer to prevent diffusion of arsenic from the epitaxial stack of the upper layer into the diffusion region of the germanium substrate to avoid affecting the diffusion depth of the n-type dopant. However, in addition to effectively controlling the diffusion concentration and depth of the n-type dopant, the interface smoothness and defects (such as charged particles and poor rows) between the InGaP stack and the wrong substrate also affect the photoelectric conversion efficiency of the photovoltaic cell. In view of this, there is an urgent need for the development of a III-V multi-junction solar cell, which can improve the interface smoothness and the effect of defects between the InGaP stack and the germanium substrate, in order to effectively improve the photoelectric conversion efficiency. SUMMARY OF THE INVENTION According to one embodiment of the present invention, a multi-junction photocell device includes: a germanium substrate having a shallow junction on a surface; a multi-junction stacked battery structure disposed on the germanium substrate; A superlattice structure is interposed between the stacked battery structure of the multiple junctions and the germanium substrate. In one embodiment, the superlattice structure may be a short-period superlattice structure comprising a superlattice structure epitaxial layer of a phosphorus-containing compound semiconductor. In an embodiment, the superlattice structure includes 201212247

A layer of material in which InGaxAU is alternately arranged, where χ is a value between 0 and 1. According to another embodiment of the present invention, a multi-junction photocell device includes: a germanium substrate structure having a germanium-doped germanium substrate and an n+-type shallow diffusion region, wherein a shallow η+-ρ junction is formed between a p-type doped germanium substrate and the n+ type shallow diffusion region; a superlattice structure disposed on the n+ type shallow diffusion region; and a double junction stacked cell structure disposed on the superlattice structure. The present invention will be described in detail below with reference to the accompanying drawings, in which: FIG. Reference basis of the present invention. In the drawings or the description of the specification, the same drawing numbers are used for similar or identical parts. In the drawings, the shape or thickness of the embodiment may be expanded and simplified or convenient. In addition, the components of the drawings will be described separately, and it is noted that elements not shown or described in the drawings are known to those of ordinary skill in the art, and The examples are merely illustrative of specific ways of using the invention and are not intended to limit the invention. In accordance with a primary embodiment and aspect of the present invention, a multi-junction photovoltaic cell assembly is provided that is sandwiched between a germanium substrate and a multilayer structure having at least one junction by a superlattice structure. The superlattice structure may be a short-period super-lattice (short-period 201212247 superlattice, SPSL for short), and the super-lattice structure has a significant effect of trapping defects, so that it can be effectively controlled Arsenic and phosphorus diffuse into the ruthenium substrate to enhance the effective conversion efficiency of light. Furthermore, the superlattice structure has the characteristics of improving the smoothness of the interface, controlling the diffusion of phosphorus and arsenic, and restricting the shifting movement from the lower layer. It should be noted that the superlattice structure may be an n-type heavily doped InGaxAl, _XP alternately arranged material layer, and a heterojunction between the ruthenium substrate forming a large energy gap, so that the shallow n+ in the ruthenium substrate The -p junction forms a depletion region of sufficient thickness to increase the built-in electric field and increase the photoelectric conversion current. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view showing a ruthenium substrate having a shallow p-n junction in one embodiment of the present disclosure. In Fig. 1, a wrong substrate 100, such as a P-type wrong substrate, has an n+-type shallow doped region on the surface to form a shallow n+-p junction 110. The shallow n+-p junction 110 is interposed between a p-type doped germanium substrate 101 and a phosphorus-containing n-type shallow diffusion region 120. The shallow η+-ρ junction 110 can be formed by diffusing an n-type dopant such as phosphorus and/or arsenic into the germanium-doped germanium substrate 100. It should be understood that the shallow η+-ρ junction 110 acts as the bottom cell component of the multi-junction photocell element, so the diffusion concentration and depth of the n+-type shallow doped region directly affects the optimal photovoltaic of the photovoltaic element. Conversion efficiency. 2 and 2 are schematic cross-sectional views showing a III-V multi-junction photocell device according to another embodiment of the present disclosure. Referring to FIG. 2, a III-V multi-junction photocell device 200 includes a multi-junction stacked cell structure 250 disposed on the germanium substrate 210, and a superlattice structure 220 is interposed on the multi-junction stack. The battery structure 250 is between the substrate 210. In one embodiment, the superlattice structure comprises a superlattice structure epitaxial layer of a phosphorus-containing compound semiconductor, such as an n+ type heavily doped material layer comprising 201212247, wherein x is between 0. To six to replace the heart | =. For example, the n+-type heavily-incorporated InG~All-xp is further connected to the germanium substrate and the germanium substrate is::?, the (10) heterogeneous ====2 of the depletion region increases the built-in Electric field

II InGaxM, xP structure,:

~/Main 疋, the superlattice structure composed of ιη〇3χΑ1ι, χρ laminate 22〇a22〇n produces quantum well effect or barrier effect, with trapped charge substitution or defect (such as difference row) characteristic. Therefore, proper adjustment of the detailed structure of the InGaP/InAlP superlattice can improve the interface=smoothness, control the diffusion of the disc and Kun in the upper compound semiconductor structure into the germanium substrate, and restrict the shifting movement from the lower layer. In the embodiment, the InGaP/InAlP superlattice may be n+ doped InG p sarcophagus

And an alternating stack structure of n + doped ^ 8 kg epitaxial layer, the thickness of each InGaP stray layer and the Ιη ΑΙΡ epitaxial layer of the layer structure may be between 10 and 50 angstroms (A), which is substantially repeated 3~ 20 cycles. The doping of the /Doped InGaP Pu's n+ doped InA1P layer is, for example, yttrium (Te)' doping concentration range is generally between 1018 and 10i9 cm-3 because the InGaP/InAlP superlattice structure is n+ doped Therefore, the n+-type shallow doped region of the p-type germanium substrate of the layer can be formed as a heterojunction. In general, the n+ type shallow doped region is very thin, so that with the aid of the n+ doped InGaP/InAlP superlattice structure, a carrier thickness depletion region of sufficient thickness can be generated in the p-type germanium substrate, and A large enough built-in electric field to effectively generate electronic electricity / the same point 201212247. In another embodiment, the n+ doped InGaP/InAlP superlattice structure may be directly formed on the p-type germanium substrate instead of forming an n+ type shallow doped region. It should be understood that the superlattice structure disclosed in the above embodiments is not limited to the InGaxAU stack, and may be replaced with other suitable compound semiconductor materials without departing from the scope of the present invention. The superlattice material must match the lattice constant of the underlying germanium substrate, and its energy gap (eg, InGaxAU's energy gap 1.86eV) should be greater than the energy gap of the p-type germanium substrate (eg, the energy gap of Ge is 0.67eV). That is, the selected superlattice material does not absorb long-wavelength incident light. Furthermore, the high-gap heterogeneous p-n junction should produce a sufficient thickness of the carrier depletion region to produce a sufficient number of electron-hole separations, but it should be noted that excessive thickness will result in increased resistance. The superlattice structure 220 can be formed by physical or chemical deposition methods such as organometallic vapor phase epitaxy (MOVPE), organometallic chemical vapor deposition (MOCVD), and atomic layer deposition (ALD). Or other suitable deposition methods for epitaxial growth on a germanium substrate. • Referring again to Figure 2A, the multi-layer stack cell structure 250 having at least one junction can be a single junction or a double junction multilayer semiconductor structure. In one embodiment, a double-layered compound semiconductor structure 250 comprising InGaP and (In) GaAs is disposed on the superlattice structure 220. The multilayer compound semiconductor structure 250 can be a stacked structure including, for example, a GaAs buffer layer 232, an intermediate cell component (eg, a GaAs secondary cell stack) 236, and a top cell component (eg, an InGaP secondary cell stack) 244. A first tunnel junction 234 is interposed between the GaAs buffer layer 232 and the intermediate cell element 236, and a second tunnel junction 242 is interposed between the intermediate cell element 236 and the top cell element 201212247. The combination of a double junction phosphor compound semiconductor structure and a germanium substrate having a shallow pn junction (which can be regarded as a bottom cell element) can constitute a triple-junction solar cell 'effectively extending the upper limit of the wavelength of the solar absorption spectrum The range is up to 800 nm, and the photovoltaic element 200 is optimized for photoelectric conversion efficiency. The present invention has been disclosed in the above various embodiments, and is not intended to limit the scope of the present invention. Any one of ordinary skill in the art can change the scope of the invention without departing from the spirit and scope of the invention. Retouching. The scope of the invention is defined by the scope of the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view showing a ruthenium substrate having a shallow p-n junction according to an embodiment of the present disclosure. 2A and 2A are cross-sectional views showing a III-V multi-junction photocell device according to another embodiment of the present disclosure. [Main component symbol description] 100 wrong substrate ιοί P-type substrate 110 shallow pn junction 120 phosphorus-containing η Type shallow diffusion region 200 III-V multi-junction photocell element 210 锗 substrate 220 superlattice structure 220a-220n alternating InGaxAl] _xP lamination 232 GaAs buffer layer 9 201212247 234 first tunnel junction 235 intermediate battery element 236 Multi-layer battery structure of battery element 242 with second tunneling surface 244 and at least one junction of top battery element 250

Claims (1)

201212247 VII. Patent application scope: 1. A multi-junction photovoltaic cell component, comprising: a germanium substrate having a shallow junction on the surface; and a plurality of stacked battery structures disposed on the germanium substrate; and a superlattice The structure is sandwiched between the stacked battery structure of the multiple junctions and the crucible base. Layer 2 (4) The multi-junction photovoltaic cell component described in the first paragraph of the patent scope, wherein the lattice structure includes a superlattice structure containing a compound semiconductor, and is described in the first item of the patent scope. A multi-junction photovoltaic cell component, wherein the superlattice structure comprises a short-range superlattice structure. The multi-junction photocell element described in the first paragraph of the patent scope of the invention has a :: super-including material layer containing 1nGaxAll and xP alternately arranged, and the eighth is X; The value between. Tt. The multi-junction photovoltaic cell component described in claim 4, wherein the material layers alternately arranged by stone Ι, Α1ι·χΡ include - n+ type doped Λ2 t-n+ type doped In Aip worm layer In the alternating laminated layer of the fourth embodiment of the present invention, the multi-junction photocell device according to claim J, wherein the energy gap of the superlattice structure in the 201212247 energy gap is greater than that of the tantalum substrate; Patent scope! The multiple diffusion regions described in the item. The multi-junction photocell device according to the first aspect of the present invention, wherein the multi-junction photovoltaic cell structure comprises a multilayer compound 10. A multi-junction photovoltaic element comprises: (4) A = plate structure has - doped wrong substrate and ~ η + type shallow diffusion: two shallow " junction formation between the p-type hybrid substrate and the n-type shallow diffusion region; a superlattice The structure is disposed on the n+ type shallow diffusion region; and the double junction stacked battery structure is disposed on the superlattice structure. 11. The multi-junction photocell device according to the above-mentioned claim, wherein the superlattice structure comprises a superlattice structure of a phosphorus-containing compound semiconductor. The multi-junction photocell device of the above aspect, wherein the superlattice structure comprises a short-period superlattice structure. 13. The multi-junction photovoltaic cell component of claim 1, wherein the 5H superlattice structure comprises a layer of material comprising AlGa/U alternately arranged, wherein x is a value between 0 and 1. . The multi-junction photocell element according to claim 13, wherein the material layer comprising the InGaxAlP alternating arrangement comprises an n+ type doped InGaP doped layer and an n+ type doped layer The alternating stack structure of the Ιη ΑΙΡ 晶 layer, wherein the thickness of each of the InGaP epitaxial layer and the Ιn ΑΙΡ epitaxial layer of the alternating stacked structure may range from 1 〇 to 50 Å and is substantially repeated for 3 to 20 cycles. 15. The multi-junction photocell device of claim 10, wherein the superlattice structure forms a foreign junction with the germanium substrate. 16. The multi-junction photocell device of claim 10, wherein the superlattice structure has an energy gap greater than an energy gap of the germanium substrate. 17. The multi-junction photovoltaic cell component of claim 10, wherein the dual junction stacked battery structure comprises an intermediate battery component and a top battery component.