CN211150576U - High-temperature solar photoelectric conversion structure based on photon-enhanced thermionic emission - Google Patents

Abstract

The utility model belongs to the field of solar energy composite utilization. In order to solve the technical problems of low energy conversion efficiency and working life of PETE devices and insufficient output current when a solar energy composite utilization system using vacuum PETE devices works at high temperature in the prior art, a solar energy composite utilization system is provided. An all-solid-state high-temperature solar photoelectric conversion structure based on photon-enhanced thermionic emission, including a positive electrode layer, an absorption layer, a barrier layer and a negative electrode layer arranged in sequence from top to bottom; the absorption layer adopts a P-type heavily doped narrow Forbidden band semiconductor material; the barrier layer adopts a semiconductor material with a forbidden band width greater than that of the absorption layer; the conduction band barrier at the interface between the barrier layer and the absorption layer is smaller than the valence band barrier; the negative electrode layer is made of metal material; the positive electrode layer is made of metal material, and the positive electrode layer and the absorption layer are partially overlapped; or, the positive electrode layer is made of a transparent metal oxide conductive film layer material with a whole surface or grid structure.

Description

A high-temperature solar photoelectric conversion structure based on photon-enhanced thermionic emission

technical field

The utility model relates to a solar energy composite utilization battery, in particular to a high-temperature solar energy photoelectric conversion structure based on photon-enhanced thermal electron emission.

Background technique

Solar energy is a safe and environmentally friendly renewable energy. Under the background of energy crisis and environmental degradation, the efficient use of solar energy has received extensive attention and research. Solar thermal power generation and photovoltaic power generation are the two main solar power generation methods.

Solar thermal power generation is to collect solar energy as thermal energy, and then use thermoelectric devices to convert it into electrical energy. Solar thermal power generation can utilize the energy of the full spectrum of the sun, but the conversion efficiency is low. Photovoltaic power generation uses photovoltaic cells to directly convert solar energy into electrical energy, which has high conversion efficiency, but can only respond to solar energy in part of the spectrum according to the material of photovoltaic cells.

Since photovoltaic cells will generate waste heat that cannot be used, if the waste heat of photovoltaic cells can be coupled to the back-end thermoelectric devices for use, and the photovoltaic cells and thermoelectric devices can be combined into a composite utilization system, the total energy conversion efficiency can be greatly improved. However, in existing photovoltaic cells, the built-in field for classifying photogenerated carriers decreases rapidly with the increase of temperature until it disappears, so that the conversion efficiency of the existing photovoltaic cells decreases rapidly with the increase of temperature, and cannot work in a high temperature environment. As a result, the thermal coupling temperature of the current solar energy composite utilization system is very low, and the back-end thermoelectric devices cannot effectively output electric energy.

In 2010, researchers at Stanford University proposed a new concept for the efficient use of solar energy, called the Photon-Enhanced Thermionic Emission Effect (PETE Effect). Their proposed device consists of a semiconductor cathode and a low work function anode encapsulated in a vacuum environment. The cathode receives focused light and is in a high temperature state, and the anode is in a low temperature state because it is vacuum isolated from the cathode. When not illuminated, it is similar to an ordinary thermoelectric emitting device. When illuminated, a large number of photogenerated electrons will be generated in the cathode conduction band. These electrons can easily obtain sufficient kinetic energy at high temperature to be emitted into a vacuum, and then collected by the anode to generate a current output. Electrons absorb photon energy across the band gap, absorb thermal energy and emit into the vacuum. Because the photon energy and photo-generated heat energy are simultaneously utilized in the thermionic emission process of photo-generated electrons, the PETE device has a high conversion efficiency, and the theoretical efficiency is higher than 38%. Because the PETE device can work at high temperature, it can be combined with the heat engine to form a high-efficiency composite utilization system. The conversion efficiency of the solar energy composite utilization system composed of it can exceed 50% according to theoretical calculations.

However, in practical application research, it is found that there are many technical difficulties and challenges that are difficult to solve in the vacuum structure PETE device: the active layer on the surface of the PETE cathode used to reduce the electron affinity of the material will be decomposed and desorbed unstable at high temperature, which will Reduce the energy conversion efficiency and working life of the PETE device; the use of a vacuum structure will introduce space charge effects when the emission current is large, reducing the output current of the PETE device; under high temperature conditions, the vacuum degree of the PETE device will decrease, which will seriously affect the PETE device. The working performance and lifespan put forward strict requirements on the vacuum packaging process and cleanliness of the device. The above technical problems have become the bottleneck of PETE effect research, hindering the practical development of PETE technology.

Utility model content

The main purpose of the utility model is to solve the technical problems such as low energy conversion efficiency and working life of PETE devices and insufficient output current when the solar energy composite utilization system utilizing the PETE effect in the prior art works at high temperature, and provides a photon-enhanced thermal energy Electron-emitting high-temperature solar photoelectric conversion structure.

To achieve the above object, the utility model provides the following technical solutions:

A high-temperature solar cell structure based on photon-enhanced thermionic emission, which is special in that it includes a positive electrode layer, an absorption layer, a potential barrier layer and a negative electrode layer arranged in sequence from top to bottom; the absorption layer adopts a forbidden band A semiconductor material with a width of 0.8-2.1 eV; the barrier layer adopts a semiconductor material with a forbidden band width greater than that of the absorption layer; the conduction band barrier at the interface between the barrier layer and the absorption layer is smaller than the valence band barrier; the negative The electrode layer is made of metal material;

The positive electrode layer is made of metal material, and the positive electrode layer and the absorption layer are partially overlapped;

Alternatively, the positive electrode layer is made of a transparent metal oxide conductive film layer material with a whole surface or a grid structure.

Further, a light-transmitting buffer layer is also arranged between the positive electrode layer and the absorption layer.

Further, the absorption layer adopts P-type heavily doped semiconductor material.

Further, the thickness of the barrier layer is 10-100 nm.

Further, a light condensing device is arranged above the positive electrode layer.

Further, the absorption layer adopts GaAs, CdTe, GaN or Si, and the corresponding barrier layer adopts AlGaAs, CdZnTe, AlGaN or diamond.

Compared with the prior art, the beneficial effects of the present utility model are:

1. The present invention is a high-temperature solar photoelectric conversion structure based on photon-enhanced thermionic emission, which is an all-solid-state solar cell structure, and its electron barrier height can be adjusted by selecting the materials of the absorption layer and the barrier layer and adjusting the doping of the barrier layer. The concentration method is arbitrarily controlled, and is not affected by the temperature rise. It can effectively carry out solar photoelectric conversion without external cooling. As a core device, it forms an ideal solar photothermal composite utilization system with a focusing device and a heat engine to further improve the conversion. In addition, its structure is similar to that of traditional semiconductor devices, and the process is compatible. It can learn from mature crystal growth and chip manufacturing technology, which is beneficial to the practical application of PETE effect technology. The solar photoelectric conversion structure of the present invention has no space charge effect, and the adverse effect of the electrostatic potential barrier on the output current can be reduced or even eliminated by modulating and doping the potential barrier layer. The charge-selective barrier layer structure is formed by the energy band discontinuity of the heterojunction interface, which can separate and output photogenerated carriers based on the PETE effect. Furthermore, the barrier layer is made of semiconductor materials with a band gap larger than that of the absorber layer, which can form a good heterojunction interface with the absorber layer, and the negative electrode layer can form a low-defect heterojunction cross-section with the barrier layer, which has a lower cross-section. Series resistance.

2. The buffer layer of the present invention is located between the positive electrode layer and the absorption layer, and is used to reduce the interface recombination caused by defects at the interface.

3. The absorption layer of the present invention adopts P-type heavily doped semiconductor material, which is used for absorbing solar photons to generate photo-generated electron-hole pairs.

4. The thickness of the barrier layer of the present invention is 10-100 nm, which ensures that the photogenerated electrons cross the barrier layer in the way of thermal electron emission.

5. The positive electrode layer of the present invention is provided with a concentrating device, so that the solar cell structure can work under focused sunlight.

Description of drawings

Fig. 1 is the structural representation of the first embodiment of the present utility model;

Fig. 2 is the structural representation of the second embodiment of the present utility model;

3 is a schematic structural diagram of Embodiment 3 of the present utility model;

FIG. 4 is an energy level structure diagram of the solar photoelectric conversion structure according to the second embodiment of the present invention (the arrow in the figure indicates the direction of incident light).

Among them, 1 - positive electrode layer, 2 - buffer layer, 3 - absorption layer, 4 - barrier layer, 5 - negative electrode layer.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention and the accompanying drawings. Obviously, the described embodiments do not limit the present invention.

Compared with the PETE device with the existing vacuum structure, the utility model cancels the vacuum layer, and fundamentally solves the high temperature desorption of the cathode active layer material faced by the vacuum PETE device, the space charge effect reduces the output current, and the high temperature is difficult to maintain at high temperature. Problems such as vacuum are beneficial to the practical development of PETE effect.

Example 1

As shown in Figure 1, a high-temperature solar photoelectric conversion structure based on photon-enhanced thermionic emission includes a positive electrode layer 1, an absorption layer 3, a barrier layer 4 and a negative electrode layer 5 arranged in sequence from top to bottom, and the positive electrode layer 1 A light-transmitting buffer layer 2 is also provided between the absorbing layer 3 . The positive electrode layer 1 is made of a transparent metal oxide material; the absorption layer 3 is made of a narrow-bandwidth semiconductor material and is heavily doped with P type; The narrow band gap semiconductor material of the absorption layer forms a good heterojunction cross section, and the conduction band barrier formed by the two semiconductors at the interface of the absorption layer 3 and the barrier layer 4 is much smaller than its valence band barrier, and the barrier layer 4 The thickness is 10 nm; the negative electrode layer 5 is made of metal material.

Embodiment 2

As shown in FIG. 2, a high-temperature solar photoelectric conversion structure based on photon-enhanced thermionic emission includes a positive electrode layer 1, an absorption layer 3, a potential barrier layer 4 and a negative electrode layer 5 arranged in sequence from top to bottom, and the positive electrode layer 1 A light-transmitting buffer layer 2 is also provided between the absorbing layer 3 . The positive electrode layer 1 is made of metal material, and the positive electrode layer 1 is distributed on both sides at the top of the buffer layer 2, and the middle of the buffer layer 2 is exposed to absorb light; the absorption layer 3 is made of a narrow-bandwidth semiconductor material and is heavily P-type doped The barrier layer 4 is a wide-bandgap semiconductor material with a forbidden band width greater than that of the absorption layer 3, which can form a good heterojunction cross-section with the narrow-bandgap semiconductor material of the absorption layer, and is at the interface between the absorption layer 3 and the barrier layer 4. The conduction band barrier formed by the two semiconductors is much smaller than the valence band barrier, and the thickness of the barrier layer 4 is 100 nm; the negative electrode layer 5 is made of metal material.

Figure 4 is the energy level structure diagram of the solar photoelectric conversion structure of the second embodiment, wherein: E _F is the Fermi level; E _g1 is the forbidden band width of the absorption layer 3; E _g2 is the forbidden band width of the barrier layer 4 _{ΔEC is the energy difference of the conduction band, that is, the barrier of the conduction band; ΔE V is the energy difference of the valence band, that is, the barrier of the valence band; VC is the potential} barrier of the absorption layer 3;

Embodiment 3

As shown in FIG. 3 , a high-temperature solar photoelectric conversion structure based on photon-enhanced thermionic emission includes a positive electrode layer 1 , an absorption layer 3 , a barrier layer 4 and a negative electrode layer 5 arranged in sequence from top to bottom. The positive electrode layer 1 adopts a light-transmitting metal oxide with a grid structure; the absorption layer 3 adopts a semiconductor material with a narrow bandwidth and is heavily P-type doped; It can form a good heterojunction cross-section with the narrow band gap semiconductor material of the absorption layer, and the conduction band barrier formed by the two semiconductors at the interface of the absorption layer 3 and the barrier layer 4 is much smaller than its valence band barrier, and the potential The thickness of the barrier layer 4 is 60 nm; the negative electrode layer 5 is made of metal material.

A light-transmitting buffer layer 2 can also be arranged between the absorption layer 3 and the positive electrode layer 1 in the third embodiment, so as to reduce the interface recombination caused by defects at the interface.

In the above-mentioned Embodiments 1 to 3, the absorption layer 3 is used for absorbing solar photons to generate photo-generated electron-hole pairs, and the barrier layer 4 is a wide-bandgap semiconductor material with a forbidden band width greater than that of the absorption layer 3. The narrow band gap semiconductor material forms a good heterojunction interface, and the conduction band barrier formed by the two semiconductors at the interface is much smaller than its valence band barrier; the absorption layer 3 uses a narrow band gap semiconductor material, and the band gap is 0.8 -2.1eV; the buffer layer 2 is located between the material of the positive electrode layer 1 and the absorber layer 3 to reduce the interface recombination caused by defects at the interface; the positive electrode layer 1 can be a metal material, or a transparent conductive layer or has grid bars A metal oxide layer with a light-transmitting structure, which can form a low-impedance electrical contact with the buffer layer 2 or the absorption layer 3 to reduce the series resistance of the device; the semiconductor materials that can be used for the absorption layer 3 and the barrier layer 4 include but are not limited to : GaAs/AlGaAs, CdTe/CdZnTe, GaN/AlGaN and Si/diamond; the negative electrode layer 5 is a metal layer, which can form a low-defect heterojunction interface with the barrier layer 4 and has a low series resistance. Different from vacuum PETE devices, it uses wide-bandgap semiconductor material as the barrier layer instead of the vacuum layer, and the charge-selective barrier layer structure is formed by the energy band discontinuity at the interface of the heterojunction, and the photo-generated current is separated and output based on the PETE effect. son.

The high-temperature solar cell based on photon-enhanced thermionic emission can receive direct illumination from focused sunlight, and a condensing device, such as a condensing mirror, can be arranged above the positive electrode layer 1 . The absorption layer 3 absorbs incident focused sunlight, excites electrons to the conduction band of the material of the absorption layer 3 according to the internal photoelectric effect, and generates holes in the valence band, thereby generating photogenerated carriers. After these photogenerated carriers are generated, they will be transported to the heterojunction interface between the absorption layer 3 and the barrier layer 4 . Since the forbidden band width of the barrier layer 4 is much larger than that of the absorption layer 3, its valence band energy difference is much larger than the conduction band energy difference. After the photogenerated electrons reach this interface, due to the small conduction band barrier they face, they can be easily heated by heat. The electrons are emitted through the barrier layer and output to the external circuit, while the photogenerated holes will face a very high valence band barrier in the valence band, and it is almost impossible to output across the barrier layer. Since the barrier layer 4 with this energy level structure can realize the selective output of photogenerated electrons, it can also be referred to as a charge-selective barrier layer structure. In order to ensure that the photo-generated electrons cross the barrier layer 4 in the way of thermal electron emission, it is necessary to ensure that the thickness of the barrier layer 4 is between 10-100 nm. The absorption layer 3 is made of heavily doped semiconductor material, and the barrier layer 4 is made of wide-bandgap semiconductor material to ensure that its energy band structure can be maintained at high temperature, so that its working mechanism is still effective. Therefore, the high-temperature solar photoelectric conversion structure based on photon-enhanced thermionic emission can effectively convert sunlight energy into electrical energy output under high temperature conditions.

Compared with the PETE device of vacuum structure, the high-temperature solar photoelectric conversion structure of photon-enhanced thermionic emission does not require surface activation, and its electron barrier height can be adjusted by selecting the materials of the absorption layer 3 and the barrier layer 4 and adjusting the doping of the barrier layer 4 The concentration is arbitrarily controlled; no space charge effect is introduced, and the adverse effect of the electrostatic potential barrier on the output current can be reduced or even eliminated by modulating and doping the barrier layer 4; its structure is similar to that of traditional semiconductor devices, and the process is compatible. The mature crystal growth and chip manufacturing technology can be used for reference, which is beneficial to the practical application of the device; as a photoelectric conversion device that can work at high temperature, the all-solid PETE device of the present invention can be used as a core device, forming an ideal solar light with a focusing device and a heat engine. The thermal composite utilization system further improves the conversion efficiency.

The above are only the embodiments of the present utility model, and are not intended to limit the scope of protection of the present utility model. Any equivalent structural transformation made by using the contents of the present utility model description and accompanying drawings, or directly or indirectly applied in other related technical fields, All are included in the scope of patent protection of the present invention.

Claims (6)

1. A high-temperature solar photoelectric conversion structure based on photon-enhanced thermionic emission is characterized in that: comprises a positive electrode layer (1), an absorption layer (3), a barrier layer (4) and a negative electrode layer (5) which are arranged from top to bottom in sequence;

the absorption layer (3) is made of a semiconductor material with the forbidden band width of 0.8-2.1 eV;

the barrier layer (4) is made of a semiconductor material with a forbidden band width larger than that of the absorption layer (3); the conduction band barrier at the interface of the barrier layer (4) and the absorption layer (3) is smaller than the valence band barrier;

the negative electrode layer (5) is made of a metal material;

the positive electrode layer (1) is made of a metal material, and the positive electrode layer (1) is partially overlapped with the absorption layer (3);

or, the positive electrode layer (1) adopts a transparent metal oxide conductive film layer material with a whole surface or grid structure.

2. The high-temperature solar photovoltaic conversion structure based on photon-enhanced thermionic emission as claimed in claim 1, wherein: a light-transmitting buffer layer (2) is arranged between the positive electrode layer (1) and the absorption layer (3).

3. A high temperature solar photovoltaic conversion structure based on photon enhanced thermionic emission as claimed in claim 1 or 2, wherein: the absorption layer (3) is made of a P-type heavily doped semiconductor material.

4. The high-temperature solar photovoltaic conversion structure based on photon-enhanced thermionic emission as claimed in claim 3, wherein: the thickness of the barrier layer (4) is 10-100 nm.

5. The high-temperature solar photovoltaic conversion structure based on photon-enhanced thermionic emission as claimed in claim 4, wherein: a light gathering device is arranged above the positive electrode layer (1).

6. The high-temperature solar photovoltaic conversion structure based on photon-enhanced thermionic emission as claimed in claim 5, wherein: the absorption layer (3) is made of GaAs, CdTe, GaN or Si, and the corresponding barrier layer (4) is made of AlGaAs, CdZnTe, AlGaN or diamond.

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