CN101236795A - Amorphous silicon multijunction nuclear battery - Google Patents

Abstract

The invention discloses a design proposal of an atomic battery for converting nuclear energy into electric energy. The invention makes the voltage and output power of the beta-voltaic (beta-voltaic) battery based on amorphous silicon greatly enhanced through the multi-nodule battery formed by overlapping multi-junction amorphous silicon p-i-n type batteries. In such amorphous silicon multi-junction beta accumbens cells, beta radiation can also be provided by contact layers placed between and outside the amorphous silicon p-i-n structures.

Description

Amorphous silicon multi-nodule cell

technical field

The present invention relates to the description of nuclear batteries, especially nuclear batteries related to beta rays. Raw energy based on nuclear cells with a p-i-n structure made of thin films of amorphous silicon, provided by beta radiation. The invention particularly relates to a technique for greatly improving the stability of a multi-junction tritiated amorphous silicon β-volt battery, thereby greatly prolonging its reliable power supply period.

Background technique

In recent years, various electronic devices are widely popular all over the world, which greatly increases the demand for batteries. The life of the commonly used chemical batteries is about several hours, and the chemical batteries are relatively heavy. It is difficult to dispose of the waste batteries after use, and the storage life of the chemical batteries is limited. There is strong demand. Atomic batteries are one solution.

The meaning of this "battery" refers to one or more connected units that can provide power. The "nuclear battery" is also called "atomic energy battery", which refers to the energy of this battery Derived from the energy stored in the nucleus of the atom. The nuclear energy stored in the nucleus is usually released in one of three ways: nuclear fission, nuclear catastrophe, and radioactive disintegration. The present invention is based on the conversion of nuclear radiation (beta rays) released by nuclear disintegration into electrical energy using semiconductor structures. Several such nuclear batteries, relying on radioactive disintegration, have been invented over the decades based on a single-step conversion process or a two-step conversion process. The single-step conversion atomic energy battery directly converts nuclear radiation into electrical energy, and the double-step conversion battery converts nuclear radiation energy into an intermediate energy source (such as heat or light), which is further converted into electrical energy.

Single-step conversion types of nuclear batteries include beta volt batteries, which operate by exposing a conventional crystalline semiconductor p-n junction to nuclear radiation, resulting in the generation of electron-hole pairs that induce low-voltage current flow. An example of this is provided in US Patent Nos. (2745973 and 4024420). Another example of a single-step conversion nuclear battery is a low-voltage battery, which is based on the principle of gas ionization, and therefore contains an ionized gas battery. The battery consists of an ionized gas and two electrodes placed between the gas The electric field is established between them, and the nuclear radiation source can be gaseous or solid. Another example is a high-voltage vacuum battery, in which one electrode constitutes a source of charged ions for nuclear radiation, while the other electrode has high receiving efficiency and low re-radiation energy, which leads to efficient collection of nuclear radiation, thus making high-efficiency Nuclear power devices with low voltage and low current.

The double-step conversion nuclear battery includes a photovoltaic cell. Its working principle is to first irradiate nuclear radiation on a fluorescent material to convert it into light energy, and then expose the semiconductor p-n junction to light, thereby generating low-voltage current according to the photovoltaic effect. There is also a two-step nuclear battery that is thermoelectric. Its working principle is to convert nuclear radiation into heat energy first, and then convert the heat energy into electrical energy through the thermoelectric effect. Examples of photovoltaic and photothermonuclear cells include the following US Patent Nos. 4,628,143; 4,900,368 and 5,008,579.

The conversion of nuclear energy into electrical energy is usually very inefficient. The efficiency of this single-step nuclear power conversion process is usually below 5%, and the efficiency of the two-step nuclear battery conversion process is even lower. In reality, the limitation of nuclear battery conversion comes from the energy loss of nuclear energy before it reaches the semiconductor, and the further attenuation of nuclear radiation in the semiconductor material, and finally only a small part can be used to generate harvestable energy near the p-n junction. electron-hole pairs.

In order to solve the above difficulties, US Patent No. 5606213 proposes a β-volt battery based on amorphous silicon. The composition of this nuclear battery is to chemically incorporate radioactive tritium into the amorphous silicon material. Usually amorphous silicon contains hydrogen (hydrogenated amorphous silicon is also often referred to simply as amorphous silicon). In tritiated amorphous silicon, tritium atoms are uniformly distributed throughout the silicon network in the form of chemical bonds. Another point of view for considering this material is that some hydrogen is replaced by tritium in hydrogenated amorphous silicon.

Figure 1 demonstrates a state-of-the-art nuclear battery consisting of tritiated amorphous silicon p-i-n structures. It consists of a p-layer 16 ("p-type region" doped with boron), an n-layer 19 (an "n-type region" doped with phosphorus), and an i-layer 18 (intrinsic or doped region) . The p-layer 16 and n-layer 19 of amorphous silicon, which can also be based on tritiated amorphous silicon, are placed on both sides of the i-layer 18 of tritiated amorphous silicon. According to the design of this device, most of the β-ray energy source is provided by the tritiated amorphous silicon i-layer 18, which is at least an order of magnitude thicker than the p-layer 16 and n-layer 19. The idea is to embed tritium directly into semiconductors that convert nuclear energy into electrical energy, thereby reducing the loss of nuclear radiation energy and simplifying the structure of nuclear batteries.

Unfortunately, the performance of tritiated amorphous silicon beta accumbens cells is too unstable, and the power conversion efficiency has not yet reached 1%. The specific rate of decay depends on the concentration of tritium in the i-layer 18, usually 10%. In the tritiated amorphous silicon i-layer 18, the voltage of the p-i-n type beta accumbens cell is only in the range of tens of nanovolts, which is much lower than one microvolt. Such a low voltage cannot be used as a power battery for any common device.

Furthermore, the efficacy of such batteries decays rapidly over time. Compared with the expected service life of 12 years, the output power of the battery declines by more than 50% within a few weeks after the battery is manufactured, and the specific decline rate depends on the content of tritium in the i-layer 18 . Apparently, the electron mass of the amorphous silicon i-layer 18 degrades rapidly due to the strong reaction of helium to the decay of tritium as tritium releases electrons through beta decay to helium.

Therefore, the traditional tritiated amorphous silicon i-layer battery is not practical.

Contents of the invention

Based on the above considerations, the applicant has drawn up the purpose of the present invention to provide a beta accumbens battery based on an amorphous silicon p-i-n structure with greatly improved stability.

A further object of the present invention is to provide a multi-junction with excellent energy conversion efficiency based on the p-i-n structure of amorphous silicon, which is composed of tritiated silicon thin film p-layer and n-layer and amorphous silicon i-layer not containing non-radioactive elements. β nucleus accumbens battery.

The third object of the present invention is to provide a multi-junction beta accumbens battery based on the p-i-n structure of amorphous silicon, with external beta radiation sources on both sides of the p-i-n thin film battery.

In order to achieve the purpose of the above invention, the present invention adopts the structure of p-i-n multi-junction β-volt battery based on amorphous silicon. A polytube battery consists of a group of batteries connected end to end. Each junction cell is composed of p-layer and n-layer based on silicon thin film with intrinsic i-layer placed between them. The n-layer of the front cell is closely connected to the p-layer of the rear cell, so that the p-layer and n-layer of the adjacent cell have good, barrier-free electrical contact.

Multi-junction p-i-n type β-volt batteries are tightly and orderly connected, and the total voltage of the multi-junction battery is the sum of the voltages of the individual cells. Therefore, even if the voltage per junction cell is small, the voltage of a multi-junction cell can be greatly increased if enough cells are connected in series. Moreover, many multi-junction batteries can be connected in series to further increase the power provided to the external load.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Figure 1 shows a traditional tritiated amorphous silicon p-i-n type β-volt battery with intrinsic i layer composed of tritiated amorphous silicon.

Figure 2 shows the layered structure of an amorphous silicon p-i-n type multi-junction β-volt battery composed of a p-i-n type β-volt battery composed of tritiated amorphous silicon and its alloys with a multi-junction p-layer and n-layer.

Figure 3 shows the layered structure of an amorphous silicon multi-junction β-volt cell with external β-radiation sources placed on both sides of the multi-junction p-i-n type β-volt cell.

Detailed ways

The present invention can be demonstrated by FIG. 2 . This figure shows the structure of a multi-junction beta volt cell based on amorphous silicon p-i-n type. A polytube battery consists of a group of batteries connected end to end. Each junction cell is composed of p-layer 6 and n-layer 9 based on silicon thin film with intrinsic i-layer 8 interposed between them. The n-layer of the front cell is closely connected to the p-layer of the rear cell, so that the p-layer 6 and n-layer 9 of the adjacent cell have good, barrier-free electrical contact.

Multi-junction p-i-n type β-volt batteries are tightly and orderly connected, and the total voltage of the multi-junction battery is the sum of the voltages of the individual cells. Therefore, even if the voltage per junction cell is small, the voltage of multi-junction cells can be greatly increased if they are connected in series. Moreover, many multi-junction batteries (they are composed of multiple batteries with the structure shown in FIG. 2 ) can be connected in series, thereby further increasing the power supplied to the external load.

Because of the high doping level, the amorphous silicon-based p-layer 6 and n-layer 9 have high defectivity, electrons and holes generated therein are quickly recombined and lost, and cannot be used to convert nuclear energy into electrical energy. The i-layer 8 must maintain a low electron defect density. Therefore, tritiated amorphous silicon is not the best choice for the i-layer 8 because the helium atoms carry a large amount of kinetic energy during tritium beta decay. This energy is absorbed by the silicon matrix, and some silicon bonds are broken, creating defects such as dangling bonds. In contrast, electrons (beta particles) with energies of several thousand electron volts released by tritium beta decay do not cause any damage to the atomic structure of amorphous silicon, because electrons are much lighter than silicon. Thus, according to the invention, tritium is added only to the doped p-layer 6 and n-layer 9, and the i-layer 8, made of hydrogenated amorphous silicon or its alloys, is sandwiched between a tritium radiation source. Importantly, to ensure high quality, i-tier 8 does not contain tritium or other radioactive elements. Intrinsic hydrogenated amorphous silicon or its wide bandgap alloy with a thickness between 100 and 500 nm is the preferred material for the i-layer 8 . Beta particles produced by tritium decay penetrate an average thickness of 500 nm in silicon. The multi-junction arrangement ensures that the active conversion i-layer 8 easily receives and absorbs the beta radiation generated by the p-layer 6 and n-layer 9 without being damaged by helium atoms, which are doped Layer absorption.

Another advantage of the multi-junction cell structure is the increased utilization of the beta radiation provided by the doped p-layer 6 and n-layer 9 . In a single cell or a single p-i-n cell as shown in Figure 1, more than half of the free-guided beta radiation released by the p-layer or n-layer is received by the i-layer. On the other hand, in multi-junction cell configurations, most of the beta particles must pass through at least one doped layer surrounding the i-layer.

In order to provide sufficient current output of the β-volt battery, the tritium concentration of the p-layer and n-layer based on the tritiated silicon film must be high enough to have a range of 10-30 atomic weight percent according to the conditions for forming the silicon film. This concentration can be obtained by using silane and tritium gas to generate amorphous silicon thin films by plasma chemical vapor deposition at high pressure and relatively low temperature below 160 degrees. Furthermore, the ideal thickness of the doped layers p-layer 6 and n-layer 9 is between 20-200 nanometers, so as to provide the i-layer 8 with the maximum dose of beta radiation without causing excessive beta radiation Energy is lost in the radioactive source material (referred to as the tritiated layers p-layer 6 and n-layer 9) due to self-absorption.

As shown in Figure 3, amorphous silicon-based multi-junction beta volt cells can also be formed by placing beta radiation sources on both sides of each p-i-n cell. The connection layer 22 contains a durable beta-transition material such as tritium, nickel, beryllium placed between each pair of p-layer 26 and n-layer 29 respectively, forming a repeat 22-26-28 used in many t-p-i-n type devices -29 chains. Another beta radiation source connection layer 22 is placed under the last n-layer of the battery, an i-layer 28 based on intrinsic amorphous silicon with a repeating t-p-i-n-t-p-i-n...t-p-i-n-t structure that does not decay over time. In order to make most of the β particles released from the β radiation source connection layer 22 reach the i layer 28, the thickness of the doped layers p layer 26 and n layer 29 is at least less than 50 nm, preferably less than 30 nm.

Furthermore, as shown in FIG. 3, p layer 26 and n layer 29 can be composed of tritiated amorphous silicon and its alloys including tritiated amorphous silicon carbon, which can enhance the radiance entering i layer 28 and increase The electrical output power of a beta volt battery. That is, in order to enhance the radiance of β radiation to the i layer and increase the electrical output power of the multi-junction β volt battery, the connection layer 22 of the β volt battery can be added between and outside all the doped layers of the structure in FIG. 2 .

Since all the beta volt cells in a multi-junction beta volt cell are arranged in series, the beta radiation source connection layer 22 must be inserted as a low resistance contact layer between the silicon thin film based p-i-n type cells. Therefore, connection layer 22 must have good electrical conductivity and low resistance in contact with p-layer 26 and n-layer 29 . Bonding layer 22 is preferably composed of a metal thin film alloyed with many beta-radiating elements. Such materials can be produced by magnetron sputtering of suitable materials.

Claims (6)

1. A multi-junction β-volt battery, characterized in that: the multi-junction β-volt battery is composed of a plurality of p-i-n type β-volt batteries, and each of the p-i-n type β-volt batteries is composed of the following parts: a) a beta-radiating p-layer consisting of boron-doped tritiated amorphous silicon films (including amorphous silicon or tritiated silicon alloy films); b) a beta-radiating n-layer consisting of a phosphorus-doped tritiated amorphous silicon film (including amorphous silicon or tritiated silicon alloy films); c) one composed of intrinsic amorphous silicon or its alloys containing no radioactive components (including tritium), with a thickness in the range of 60-800 nm, placed between the p-layer and n-layer of beta radiation layer. 2. A multi-junction β-volt battery formed according to claim 1, characterized in that: the thickness of the p-layer and n-layer of the β active layer is in the range of 20-300 nanometers, and the concentration of tritium is in the range of 3-36 atomic percent within range. 3. A multi-junction β-volt battery formed according to claim 1, characterized in that: at least one layer of p-layer, i-layer and n-layer in the described multi-junction p-i-n type β-volt battery contains near-nanometer silicon and its alloy. 4. A multi-junction beta volt battery consisting of multiple cells connected in series, each cell containing: a) a p-layer consisting of a boron-doped amorphous silicon film or an alloy thereof; b) an n-layer composed of phosphorus-doped amorphous silicon film or silicon alloy; c) an intrinsic i-layer placed between said p-layer and n-layer composed of tritium or other amorphous silicon or silicon alloy without nuclear radiation components; d) A beta-active layer of sufficiently high electrical conductivity placed next to said n-layer. 5. A multi-junction β volt battery formed according to claim 4, characterized in that: the β active contact layer with sufficient electrical conductivity is placed on the p-layer described in the first cell in the multi-junction battery . 6. A multi-junction β-volt battery formed according to claim 5, characterized in that: in the multi-junction battery, at least one of the p-layer and n-layer is made of tritiated amorphous silicon film or tritiated silicon Alloy film composition.

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