Solid structural elements

Abstract

Asymmetric electrodes facing each other are conductively interconnected by means of a semiconductor material and a coating material such that an open-circuit voltage V of approximately 1.8 volts or higher is achieved by the applied electromagnetic radiation. OC .

Description

Technical Field

[0001] The invention relates to a solid-state structural element which acts on electromagnetic radiation and, depending on the embodiment, can be used as a (thermo)photovoltaic element, a photoelectric sensor, a photocatalyst, an electrical storage device or the like. Summary of the invention

[0002] The solid structural element according to the invention is defined by the features of claim 1. It comprises a cathode K (electrons exit from the cathode) and an anode A (these electrons enter the anode). The mutually opposite surfaces of the cathode K and the anode A delimit an electrode gap EZR. In the electrode gap EZR there is a semiconductor material HL and a coating material BM. The semiconductor material HL is configured as an n-type semiconductor nHL and contacts the cathode K and preferably also the coating material BM. The coating material BM contacts the anode A and preferably also the n-type semiconductor nHL.

[0003] According to the invention, the materials used have the following energy levels relative to vacuum:

[0004] i) The work function Φ of cathode K K Greater than the work function Φ of the anode A A (Φ K >Φ A ),

[0005] ii) Band gap E of n-type semiconductor nHL gHL Greater than 2.0eV (E gHL >2eV) and its Fermi energy E FnHL Greater than or (substantially) equal to the work function Φ of the cathode K K (E FnHL ≥Φ K ),and

[0006] iii) The work function of the coating material BM is smaller than the work function of the anode A (Φ BM <Φ A ) or the coating material BM has a negative electron affinity (NEA).

[0007] There is an electron-conducting contact between the cathode K, the n-type semiconductor material nHL, the coating material BM and the anode A, and the areas of the cathode (K) and the anode (A) that are not in contact with the n-type semiconductor material (nHL) or the coating material (BM) can be connected to each other via collectors and possible consumers or (in solid-state component operation) can be connected to each other via them to form a current circuit.

[0008] Preferred embodiments of the invention are set forth in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings, wherein:

[0010] Figure 1 The schematic diagram shows a solid structural element with a cathode K, a semiconductor material HL in the form of an n-type semiconductor nHL, a coating material BM and an anode A, as well as the energy levels of these components in the uncontacted state relative to a vacuum (in eV), and

[0011] Figure 2 shows that in the contact of conducting electrons, under short circuit conditions and at the electromagnetic energy h v Strip diagram of the materials used for cathode K, n-type semiconductor nHL, coating material BM and anode A when applied to cathode K.

[0012] Parts, variables and structures that correspond to one another are always provided with the same reference symbols in all the figures. DETAILED DESCRIPTION

[0013] Figure 1 The arrangement of the components of the solid structural element relative to each other is schematically shown.

[0014] Cathode K,

[0015] · semiconductor material HL in the form of an n-type semiconductor nHL,

[0016] Coating material BM and

[0017] Anode A

[0018] exist Figure 1 The above energy levels (in eV) of these components relative to vacuum in a non-contact state are also schematically shown in FIG. The mutually opposing surfaces of the cathode K and the anode A define an electrode gap EZR.

[0019] The cathode K and the anode A are formed of electron-conducting materials, which can be present either in the form of a single substance or in the form of an alloy. The electrode materials are selected in this case so that the work function Φ of the cathode K is K and the work function Φ of the anode A A as large a gap as possible.

[0020] Non-limiting examples of suitable cathode materials include:

[0021] ·Gold Au(Φ Au 4.8~5.4eV),

[0022] ·Se(Φ Se 5.11eV),

[0023] ·Platinum Pt(Φ Pt 5.32~5.66eV),

[0024] ·Ni (Φ Ni 5.0eV) and

[0025] ·Carbon C that conducts electrons, such as graphite (Φ 石墨 4.7eV).

[0026] Non-limiting examples of carbon C for conducting electrons are activated carbon cloth, graphite (in the form of particles, textile surface formations or films), fullerenes, graphene, carbon nanotubes.

[0027] Non-limiting examples of suitable anode materials include:

[0028] ·Magnesium Mg(Φ Mg 3.7eV),

[0029] ·Barium Ba(Φ Ba 1.8~2.52eV),

[0030] ·Cesium Cs(Φ Cs 1.7~2.14eV),

[0031] ·Calcium Ca(Φ Mg 2.87eV) and

[0032] ·Aluminum (Φ Al 4.0~4.2eV).

[0033] Depending on the design and the field of application of the solid component, the surfaces of cathode K and anode A forming the electrode gap EZR can be congruent or (in a mathematical sense) similar and dimensioned, for example, in the range of square micrometers or square meters.

[0034] The contact (conducting) surface of the cathode K or anode A with the semiconductor material nHL or coating material BM in the electrode gap EZR is as large as possible. Depending on the structure and field of use, the thickness of the cathode K and the anode A is different: when constructed as a photovoltaic element, for example, a thin, nanometer-thick cathode K made of gold (sheet) is used. When constructed as a (thermal) photovoltaic element, the cathode K is, for example, a micrometer or millimeter-thick graphite film or is formed by nanometer or micrometer-sized graphite particles. When constructed as an energy storage device, the size of the (porous) electrode is set in the range of decimeters or liters.

[0035] Satisfy E gnHL >2eV and E FnHL >F KSuitable n-type semiconductor materials nHL for the conditions of φ 1000 are known, for example, from Shiyou Chen and Lin Wang Wang, Chem. Mater., 2012, 24 (18), pp. 3659-3666 (Chemical Materials, 2012, Vol. 24 (No. 18, pp. 3659-3666) or J. Robertson and B. Falabretti, Electronic Structure of Transparent Conducting Oxides, pp. 27-50 in Handbook of Transparent Conductors, Springer, DOI 10.1007 / 978-1-4419-1638-9 (Electronic Structure of Transparent Conducting Oxides, Handbook of Transparent Conductors, Springer, DOI 10.1007 / 978-1-4419-1638-9). When graphite (Φ 石墨 When a cathode K of about 4.7 eV) is used, these are, as non-limiting examples, ZnO, PbO, FeTiO3, BaTiO3, CuWO3, BiFe2O3, SnO2, TiO2, WO3, Fe2O3, In2O3 and Ga2O3.

[0036] The surface of the anode A facing the electrode gap EZR is coated with a coating material BM, the work function of the coating material Φ BM It must also be smaller than the work function Φ of the anode A. A (Φ BM <Φ A ). According to the invention, for this purpose, alkali metal oxides, alkaline earth metal oxides, rare earth oxides, rare earth sulfides or binary or ternary compounds composed of these are used. According to literature data, for example, Handbook of Thermionic Properties by V.S. Fomenko and G.V. Samsonov (eds.), ISBN: 978-1-4684-7293-6 (Handbook of Thermionic Properties, ISBN: 978-1-4684-7293-6), the work function Φ of these compounds is in the range of 0.5 to 3.3 eV. Such compounds have hitherto been used for coating cathode materials of photodetectors, vacuum tubes, thermionic emitters, LEDs or the like in order to facilitate the escape of electrons from the cathode material. In the present case, it is assumed that they facilitate the entry of electrons into the material of the anode A. In addition to the above-mentioned coating materials BM, whose work function is below the vacuum reference parameter, compounds are also used whose work function is above the vacuum. These are compounds with a negative electron affinity (NEA). Hexagonal boron nitride (hBN) is mentioned as an example.

[0037] The structural element according to the invention is produced by electron-conducting contact between the above-mentioned materials. Figure 2 Shows Figure 1 The mutual energy relationship of the cathode K, n-type semiconductor material nHL, coating material BM and anode A in the short-circuit state: the interface K / nHL formed between the cathode K and the n-type semiconductor material nHL forms a Schottky contact with electron aggregation (marked with ⊕). The electron aggregation ⊕ is also assumed for the interface nHL / BM formed between the n-type semiconductor material nHL and the coating material BM. On the contrary, the interface BM / A formed between the coating material BM and the anode A is more easily tunneled by electrons (shown by a dotted line). These interfaces are not energy barriers for electrons: even at room temperature and in the dark, they can leave the lower energy level of the cathode K and enter the higher energy level of the anode A, which is indicated by the open circuit terminal voltage V OC For proof of the continuous increase of , see Example 1.

[0038] Working principle: Electromagnetic radiation with sufficient energy acting on the cathode K excites the electrons in the volume of the cathode material (directly or indirectly via phonons and plasmons) in such a way that they have the ability to leave the cathode material and enter the conduction band of the n-type semiconductor material nHL, which is (easily) possible due to the electron aggregation ⊕ existing at the interface K / nHL. If the electrons still have sufficient (kinetic) energy, they cross the interface nHL / BM into the volume of the coating material BM, so as to cross the interface BM / A into the volume of the anode A at a higher energy level. Because the n-type semiconductor material nHL has a band gap E greater than 2eV gHL , so it will not recombine with holes from the valence band.

[0039] To operate the solid-state component, the part of the cathode K without the n-type semiconductor and the part of the anode A without the coating material A are connected to form a current loop via one or more electrical conductors and possible consumers connected between them. The one or more electrical conductors and possible consumers here form an external part of the current loop that does not belong to the solid-state component according to the invention. In this operating state of the solid-state component, sufficiently "hot" electrons are able to perform electrical work, because they flow back from the anode A with a higher energy level via the external part of the current loop to the cathode K. The component is therefore also suitable as a (thermal) photovoltaic cell for converting thermal energy into electrical energy.

[0040] Known (semiconductor) technologies, such as spin coating, (electrostatic) fixing of (nano)crystals, cathode sputtering (sputtering), atomic layer deposition (ALD), epitaxy, chemical vapor deposition (CVD), physical vapor deposition (PVD), chemical bath deposition (CBD) or (electro)chemical methods can be used for contacting the corresponding conduction electrons of the materials used.

[0041] Parameters such as contact conduction conditions (temperature, pressure, gas atmosphere, air humidity, pH of the solution), the stoichiometric composition of the electrode materials and / or semiconductor materials, their roughness, their position in the thermoelectric or electrochemical electrochemical series, the formation of (dipole) layers, grain size, crystal plane orientation, crystallinity, water of crystallization (content), type and degree of lattice defects, type and degree of doping, lattice matching, layer morphology, thickness of the applied (multiple) layers, their porosity, etc., are familiar to those skilled in the art, can be varied within a wide range and can be optimized (based on the experimental results obtained).

[0042] Example 1:

[0043] Materials used:

[0044] ·The material used for the cathode is the work function Φ K 4.7 eV for graphite.

[0045] ·The material used for anode A is work function Φ A The electronegativity of magnesium is 3.7 eV.

[0046] The coating material BM used for anode A is the work function Φ BM It is 1.9eV of barium oxide.

[0047] The n-type semiconductor material nHL is tin(IV) dioxide SnO2.

[0048] According to the literature, the energy level of the conduction band LB is 5.1 eV; the Fermi energy E FSnO2 is 5.3eV, the energy level of the valence band VB is 8.6eV and the band gap E gSnO2 is 3.5eV.

[0049] Fabrication of structural elements:

[0050] I) The cathode K is brought into contact with the n-type semiconductor material nHL to conduct electrons

[0051] An activated carbon cloth (FLEXSORB FM30K) from the company "chemviron Cloth Division" of Tyne & Wear (UK) was completely immersed in a 70% (v / v) 2-propanol aqueous solution of about 2.0% (w / v) Sn(II)Cl2*2H2O for 5 hours. After removing the remaining solution, one side of the wet cloth was exposed to an ammonia atmosphere for about 12 hours. The cloth was then dried at about 50°C for several hours. The resulting silvery shiny layer is tin dioxide (IV) SnO2 (cassiterite) crystals.

[0052] II) The anode A is brought into electronic contact with the coating material BM.

[0053] A section of a magnesium strip measuring 20×3.2×0.3 mm with a length of about 17 mm is immersed in 1N hydrochloric acid for about 2 seconds, whereby the attached oxide layer is removed while hydrogen is generated. After drying with a soft tissue, about 10 μl of a saturated aqueous solution of barium oxide at about 90° C. is dripped onto the section in contact with the acid using a pipette. The strip is then heat treated with the treated side facing upward on a glassy carbon plate placed on a Bunsen burner at an estimated temperature of about 900° C. for about 30 minutes. The resulting gray layer is barium oxide BaO.

[0054] III) Assemble into solid structural elements

[0055] The anode A produced according to II) is fixed with the untreated side to the self-adhesive tape. The cathode K produced according to I) is fixed congruently with the silvery shiny side to the anode A, leaving the ends not treated with hydrochloric acid and about 2 mm of the gray BaO layer free, which results in an electron-conducting contact surface of the anode A of about 15×3.2 mm. As cathode current collector, a 0.1 mm thick copper wire is attached with the aid of adhesive tape. The ends of the magnesium strips that were not in contact with the hydrochloric acid were used as current collectors for the anodes, wherein the oxide layer located there was still mechanically removed.

[0056] The component thus produced is then placed between two glass slides, wherein the upper slide is dimensioned so that the leads of a multimeter can be connected to the current collector. The contacting of the conduction electrons of the cathode K and the anode A is achieved by pressing and fixing the two slides with the aid of a clamp. In order to further increase the operability and stability of the structural element, it can be introduced into an optically transparent 2-component epoxy resin potting compound while leaving the current collector free and then hardened.

[0057] The component produced in this way was integrated into the current circuit by connecting the (cathode) copper wire to the positive pole of a multimeter and connecting the free end of the (anode) magnesium strip to the negative pole.

[0058] When measuring the short-circuit current I sc At room temperature and indoor light, the value is 5μA / cm 2 In sunlight, by focusing the lens on the cathode K, it can reach about 2000 μA / cm 2 If directly in such an I sc After measuring the open circuit voltage V OC The measurement of V OC The value is around 0.7 V. Even at room temperature and in the dark, V OC The value will also rise to about 1.8V in about 8 hours. OC I sc The initial current value is 400 μA / cm 2 The current value then continuously decreases to about 20 μA / cm in about 20 minutes. 2 The structural element is therefore suitable for use as an energy store, more precisely in the form of a self-charging capacitor.

[0059] The open circuit terminal voltage V of the structural component (encapsulated in epoxy resin) OC The value remained constant at approximately 1.8 V over several months, which is also reflected in the lack of corrosion of anode A.

[0060] The above-mentioned dimensioning of the cathode K and the anode A is retained for the following examples.

[0061] Example 2:

[0062] TiO2 is used as n-type semiconductor nHL. Energy level: conduction band LB 4.6eV; Fermi energy E FTiO2 5.3eV; valence band VB 7.8eV and band gap E gTiO2 3.7 eV. The activated carbon cloth (cathode K) was impregnated with a 1% (v / v) solution of titanium (IV) tetraethoxide in 2-propanol and dried at 90° C. for several days. The anode A and the coating material BM were the same as in Example 1.

[0063] The contacting and assembly of the activated carbon cloth (white due to the formation of TiO2) and the BaO-coated anode A were carried out as described in Example 1. The measurement results were the same as in Example 1.

[0064] Example 3:

[0065] Fe2O3 is used as n-type semiconductor nHL. Energy level: conduction band LB 5.0eV; Fermi energy E FFe2O35.3eV; valence band VB7.3eV and band gap E gFe2O3 2.3 eV. Anode A and coating material BM are the same as in Example 1.

[0066] About 10 μl of a saturated aqueous solution of iron (III) nitrate were applied to the BaO coating surface. Drying was first carried out at room temperature and then heat-treated as in Example 1. Contacting and assembly with an unmodified activated carbon cloth (cathode K) were carried out as in Example 1.

[0067] The measurement results are the same as those in Example 1.

[0068] Example 4:

[0069] Calcium oxide CaO is used as coating material BM. The anode, again made of magnesium, is cleaned as in Example 1. Approximately 10 μl of a saturated aqueous solution of calcium nitrate Ca(NO3)2 is applied to the cleaned magnesium surface and then heat treated at approximately 900° C. Approximately 10 μl of a saturated aqueous solution of iron (III) nitrate is then applied to the CaO coating surface to form a semiconductor layer made of Fe2O3 (similar to Example 3). Drying is first carried out at room temperature and then heating is carried out as in Example 1. Contact with untreated activated carbon cloth and assembly are the same as in Example 1.

[0070] The measurement results are the same as those in Example 1.

[0071] Example 5:

[0072] Strontium oxide SrO is used as coating material BM. Anode A, again made of magnesium, is cleaned as in Example 1. Approximately 10 μl of a saturated aqueous solution of strontium nitrate Sr(NO3)2 is applied to the cleaned magnesium surface and then heat treated at approximately 900°C. Approximately 10 μl of a saturated aqueous solution of iron (III) nitrate is then applied to the coating surface with SrO in order to form a semiconductor layer made of Fe2O3 (similar to Example 3). Drying is first carried out at room temperature and then heating is carried out as in Example 1. Contact with untreated activated carbon cloth (cathode K) and assembly are the same as in Example 1. The measurement results are the same as in Example 1.

[0073] Example 6:

[0074] Cesium oxide Cs2O is used as coating material BM. Anode A, again made of magnesium, is cleaned as in Example 1. The tip of a spatula of cesium iodide CsJ is dissolved in about 10 ml of diluted KOH. 10 μl of this solution are applied to the cleaned magnesium surface and then heat treated at about 900° C. Thereafter, about 10 μl of a saturated aqueous solution of iron (III) nitrate are applied to the coating surface with Cs2O in order to form a semiconductor layer made of Fe2O3 (similar to Example 3). Drying is first carried out at room temperature and then heating is carried out as in Example 1. Contact conduction and assembly with untreated activated carbon cloth are the same as in Example 1. The measurement results are the same as in Example 1.

[0075] Example 7:

[0076] Hexagonal boron nitride hBN is used as coating material BM. The anode A, which again consists of magnesium, is cleaned as in Example 1. The tip of a spatula is dispersed in about 10 ml of diluted ethyl acetate. 10 μl of this dispersion is applied to the cleaned magnesium surface and, after evaporation of the ethyl acetate, heat treated at about 900° C. for 30 minutes. Thereafter, about 10 μl of a saturated aqueous solution of iron (III) nitrate is applied to the coating surface with hBN in order to form a semiconductor layer consisting of Fe2O3 (similar to Example 3). First dry at room temperature and then heat as in Example 1. Contact conduction and assembly with untreated activated carbon cloth are the same as in Example 1. The measurement results are the same as in Example 1.

[0077] In summary, in the solid-state component, asymmetrical electrodes, cathode K and anode A, which are located opposite each other, are connected to each other electronically by means of semiconductor material HL and coating material BM, so that an open-circuit voltage V of about 1.8 volts or even higher is achieved by the applied electromagnetic radiation. OC .

Claims

1. A solid structural element comprising - a cathode (K), said cathode being capable of being exposed to electromagnetic radiation, - anode (A), - an electrode gap (EZR), which is formed by the facing surfaces of the cathode (K) and the anode (A), - semiconductor material (HL) in the electrode gap (EZR), and - coating material (BM) in the electrode gap (EZR), in, In order to achieve electron flow between the cathode (K) and the anode (A), - the work function Φ of the material of the cathode (K) K Greater than the work function Φ of the material of the anode (A) A , The semiconductor material (HL) contacts the cathode (K) in the electrode gap (EZR) and is an n-type semiconductor material (nHL) having a band gap (E gHL ) is greater than 2.0 eV and the Fermi level (E FnHL ) is equal to or greater than the work function (Φ) of the cathode (K) K ), - the coating material (BM) contacts the anode (A) in the electrode gap (EZR), wherein the coating material (BM) has a work function Φ that is less than the work function of the anode (A) BM , or wherein the coating material (BM) has a negative electron affinity (NEA), - there is an electronically conductive contact between the cathode (K), the n-type semiconductor material (nHL), the coating material (BM) and the anode (A), and - the region of the cathode (K) not in contact with the n-type semiconductor material (nHL) and the region of the anode (A) not in contact with the coating material (BM) can be connected to one another via current collectors and possible consumers in order to form a current circuit.

2. The solid structural element according to claim 1, in, The material of the cathode (K) is electron-conducting carbon.

3. The solid structural element according to claim 1 or 2, in, The material of the anode (A) is magnesium or a magnesium alloy.

4. The solid structural element according to any one of claims 1 to 2, in, The coating material (BM) is an alkali metal oxide, an alkaline earth metal oxide, a rare earth oxide, a rare earth sulfide, or a binary or ternary compound thereof, or a material having a negative electron affinity.

5. The solid structural element according to any one of claims 1 to 2, in, The coating material (BM) is barium oxide BaO, calcium oxide CaO, strontium oxide SrO, cesium oxide Cs2O or hexagonal boron nitride hBN.

6. The solid structural element according to any one of claims 1 to 2, in, The n-type semiconductor material (nHL) is ZnO, Fe2O3, PbO, FeTiO3, BaTiO3, CuWO3, BiFe2O3, SnO2, TiO2, WO3, In2O3 or Ga2O3.

Images