A simulation method for improving the conductive capacity at the interface of a heterojunction solar cell

Abstract

The present disclosure relates to a simulation method for improving the conductivity at the interface of a heterojunction solar cell, comprising: setting a first heterojunction structure; improving the first heterojunction structure to obtain a second heterojunction structure. The first heterojunction structure and the second heterojunction structure are simulated and calculated by using simulation condition parameters to obtain a first simulation result and a second simulation result respectively; comparing the first simulation result and the second simulation result; counting the number of second simulation results greater than the first simulation result; and determining that the conductivity of the second heterojunction structure is greater than the conductivity of the first heterojunction structure when the number is greater than a predetermined number threshold. The technical solution of the present application can significantly improve the conductivity of the solar cell by setting a third material layer between the first material layer and the second material layer in the first heterojunction structure. It is beneficial to improve the efficiency of solar cell design.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a simulation method for improving the conductivity at the heterojunction solar cell interface. Background Technology

[0002] In the performance evaluation of solar cells, short-circuit current density (J) is a key metric. SC The band ratio is a key indicator determining the energy conversion efficiency of a solar cell. A heterojunction solar cell consists of two different materials, and the interface between these two materials is called the junction interface. When the band ratio of this junction interface is high, it leads to a significant decrease in short-circuit current density, affecting the conductivity of the solar cell. Summary of the Invention

[0003] To overcome the problems existing in related technologies, this disclosure provides a simulation method to improve the conductivity at the heterojunction solar cell interface, thereby solving the problem in related technologies where the conductivity at the heterojunction solar cell interface is affected by the high band ratio of adjacent materials.

[0004] According to a first aspect of the present disclosure, a simulation method for improving the conductivity at a heterojunction solar cell interface is provided, comprising:

[0005] The structure of the first heterojunction of the heterojunction solar cell includes an adjacent first material layer and a second material layer. The band step between the first material layer and the second material layer is a first band step, which is greater than a predetermined first band step threshold.

[0006] The structure of the first heterojunction is improved by setting a third material layer between the first material layer and the second material layer to obtain the structure of the second heterojunction.

[0007] In the structure of the second heterojunction, the band step between the third material layer and the first material layer is the second band step; the band step between the third material layer and the second material layer is the third band step; the sum of the second band step and the third band step is equal to the first band step;

[0008] Set multiple sets of simulation operating condition parameters;

[0009] For each set of simulation operating condition parameters, the structure of the first heterojunction and the structure of the second heterojunction are simulated and calculated using the simulation operating condition parameters, and the first simulation result and the second simulation result reflecting the conductivity are obtained respectively.

[0010] Compare the first simulation result with the second simulation result;

[0011] Within a predetermined range of horizontal coordinates, count the number of second simulation results whose amplitudes are greater than the amplitudes of the first simulation results corresponding to the horizontal coordinate variables.

[0012] If the number of simulated operating conditions is greater than a predetermined threshold for the number of simulated operating conditions, it is determined that the conductivity of the second heterojunction structure is greater than that of the first heterojunction structure.

[0013] In one implementation, the first simulation result is a first electron concentration and / or a first current density;

[0014] The second simulation result is the second electron concentration, and / or, the second current density;

[0015] The first simulation result and the second simulation result are compared, including:

[0016] The first voltage-current density curve and the second voltage-current density curve are compared in the same first coordinate system, and the first current density and the second current density corresponding to the same voltage value are compared respectively.

[0017] And / or, compare the first electron concentration distribution curve and the second electron concentration distribution curve in the same second coordinate system, and compare the first electron concentration and the second electron concentration corresponding to the same position respectively.

[0018] In one embodiment, the difference between the second band level and the third band level is less than a predetermined band level difference threshold; both the second band level and the third band level are less than a predetermined sub-band level threshold.

[0019] In one embodiment, the method further includes: determining the absolute value of the simulation result difference between the second simulation result and the first simulation result;

[0020] If the amplitude of the first simulation result is greater than the amplitude of the second simulation result, or the absolute value of the difference between the simulation results is less than the simulation result difference threshold, adjust the second band level and the third band level to control the difference between the second band level and the third band level to be less than a predetermined band level difference threshold; and / or increase the thickness of the third material layer.

[0021] In one embodiment, the method further includes:

[0022] The thickness of the third material layer is increased by a predetermined step size to obtain a sequence of the thicknesses of the third material layer.

[0023] Calculate the output short-circuit current density value of the second heterojunction structure corresponding to each third material layer to obtain the short-circuit current density sequence;

[0024] A two-dimensional curve of the thickness of the third material layer versus the short-circuit current density is generated based on the sequence of the thickness of the third material layer and the sequence of the short-circuit current density.

[0025] In one implementation, each set of simulation operating condition parameters includes: the temperature, voltage, and frequency of the heterojunction solar cell;

[0026] Multiple sets of simulation operating condition parameters are set, including: keeping the temperature and frequency of the heterojunction solar cell constant in each simulation operating condition, applying voltage to the heterojunction solar cell, and gradually increasing the voltage from a first voltage to a second voltage in a predetermined voltage step, thereby obtaining multiple sets of simulation operating condition parameters.

[0027] In one embodiment, the structure of the first heterojunction is improved by providing a third material layer between the first material layer and the second material layer, including:

[0028] The second material layer is divided into a first layer of second material and a second layer of second material;

[0029] The first layer of the second material is adjacent to the first material layer;

[0030] Modify the electrical parameters of the first layer of the second material to transform the first layer of the second material into the third material layer.

[0031] In one embodiment, modifying the electrical parameters of the first layer of the second material includes:

[0032] The electron affinity in the first layer of the second material is modified, and the first electron affinity in the first layer of the second material is modified to the second electron affinity;

[0033] The second electron affinity is between the first electron affinity and the electron affinity of the first material layer.

[0034] In one embodiment, modifying the electrical parameters of the first layer of the second material further includes:

[0035] Based on the first electron affinity and the second electron affinity, the band gap in the first layer of the second material is modified accordingly to keep the valence band top in the first layer of the second material unchanged.

[0036] In one embodiment, the first material in the first material layer is copper indium gallium selenide (CIGS); and the second material in the second material layer is cadmium sulfide (CdS).

[0037] The technical solutions provided by the embodiments of this disclosure may include the following beneficial effects:

[0038] The technical solution of this application improves the structure of the first heterojunction by placing a third material layer between the first and second material layers to mitigate the bandgap change between them, thereby significantly enhancing the conductivity of the solar cell. Simulations can determine the effectiveness of this improvement, which is beneficial for improving the efficiency of solar cell design and for creating solar cells with enhanced conductivity.

[0039] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0040] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0041] Figure 1 This is a schematic diagram of a heterojunction structure for a solar cell according to an exemplary embodiment;

[0042] Figure 2 This is a schematic diagram illustrating the effect of band order on electrons according to an exemplary embodiment;

[0043] Figure 3 This is an energy band and electron concentration distribution diagram illustrated according to an exemplary embodiment;

[0044] Figure 4 This is a flowchart illustrating a simulation method for improving the conductivity at a heterojunction solar cell interface according to an exemplary embodiment;

[0045] Figure 5 This is a comparison diagram of voltage and current curves according to an exemplary embodiment;

[0046] Figure 6 This is an electron concentration distribution comparison diagram illustrated according to an exemplary embodiment;

[0047] Figure 7 This is a two-dimensional graph of short-circuit current density versus band order, according to an exemplary embodiment.

[0048] Figure 8 This is a two-dimensional graph showing the short-circuit current density versus the thickness of the intermediate layer according to an exemplary embodiment;

[0049] Figure 9 This is a schematic diagram of a solar cell heterojunction structure with an intermediate layer provided, according to an exemplary embodiment.

[0050] Figure 10This is a comparison diagram of another voltage-current curve according to an exemplary embodiment;

[0051] Figure 11 This is a comparison diagram illustrating another electron concentration distribution according to an exemplary embodiment;

[0052] Figure 12 This is another two-dimensional graph of short-circuit current density versus band order, according to an exemplary embodiment.

[0053] Figure 13 This is another two-dimensional graph of short-circuit current density versus intermediate layer thickness, as illustrated in an exemplary embodiment. Detailed Implementation

[0054] In the following description, an embodiment of the present invention will be illustrated with reference to the accompanying drawings. The embodiments described herein are specific implementations of the invention, used to illustrate the concept of the invention, and are illustrative and exemplary, and should not be construed as limiting the implementation or scope of the invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0055] In the description of this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0056] The principles and features of the present invention are described below with reference to the accompanying drawings. The embodiments described are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0057] See appendix Figure 1 The diagram shows a heterojunction structure of a solar cell. The heterojunction of the solar cell includes a first material layer 01 and a second material layer 02. The first material layer 01 is an absorber layer and can be P-type; the second material layer 02 is a buffer layer and can be N-type. When sunlight shines on the solar cell structure, the first material layer 01 generates electricity based on the sunlight, producing electrons. These electrons enter the second material layer 02 through the interface 03 of the heterojunction.

[0058] The band structure diagram of a heterojunction solar cell under short-circuit conditions during illumination is shown below:

[0059] Figure 2 (a) shows that when the Conduction Band Offset (CBO) is less than 0.4 eV, the transport of photogenerated electrons at the heterojunction interface is unimpeded;

[0060] in, For the bottom of the conduction band; The price has reached its peak; It is the Fermi level.

[0061] Figure 2 (b) shows that when the band-order CBO is greater than 0.4 eV, the transport of photogenerated electrons at the heterojunction interface is hindered.

[0062] The extremely low electron concentration region caused by the high conduction band level at the interface is the key obstacle to photocurrent transmission. This can be explained using the semiconductor electron concentration formula:

[0063] ;

[0064] in, This represents the electron concentration at point x. Let x represent the bottom state density of the conduction band of the material at point x, k be the Boltzmann constant, and T be the operating temperature of the battery; at room temperature, kT is 0.026 eV. The bottom of the conduction band at point x.

[0065] See appendix Figure 3 In heteroband diagrams, when conduction band steps are unavoidable at the interface, there are significant differences between the two sides of the interface. Conduction band energy level difference. According to the above semiconductor electron concentration formula, this energy level difference will introduce a large electron concentration difference on both sides of the interface, thereby introducing an extremely low electron concentration in the local region of the interface.

[0066] See appendix Figure 3 The electron concentration distribution diagram within the heterojunction structure shows that when the conduction band level at the interface is 0.4 eV, the concentration near the buffer layer at the interface is as low as... This magnitude becomes the main obstacle to the transport of photogenerated electrons, leading to a decrease in the battery's output current performance. At a band size of 0.6 eV, the concentration near the buffer layer at the interface is as low as... Magnitude.

[0067] Based on this, this application proposes a simulation method to improve the conductivity at the heterojunction solar cell interface, see appendix. Figure 4 The method may include the following steps:

[0068] In step S101, the structure of the first heterojunction of the heterojunction solar cell is set.

[0069] In this embodiment, the structure includes adjacent first and second material layers. The band step between the first and second material layers is called the first band step. The first band step is obtained by subtracting the smaller of the conduction band bottoms of the first and second material layers. For example, if the conduction band bottom of the first material layer is greater than that of the second material layer, the first band step is obtained by subtracting the conduction band bottom of the second material layer from the conduction band bottom of the first material layer.

[0070] In the following embodiments, the first band order can also be referred to as the original band order, the original high band order, or the original high conduction band order.

[0071] The first band level is greater than a predetermined first band level threshold. This first band level threshold can be set flexibly; preferably, the first band level threshold can be 0.6 eV.

[0072] In step S102, the structure of the first heterojunction is improved by setting a third material layer between the first material layer and the second material layer to obtain the structure of the second heterojunction.

[0073] In the structure of the second heterojunction, the banding between the third material layer and the first material layer is called the second banding. This second banding can be referred to as a sub-banding, banding 1, or banding 2.

[0074] The zone between the third material layer and the second material layer is called the third zone. This third zone can be simply referred to as the sub-zone, zone 2, or zone 1.

[0075] The sum of the second and third band orders is equal to the first band order.

[0076] In this embodiment, an intermediate layer, referred to here as the third material layer, is disposed between the first and second material layers; in the following embodiments, it will be simply called the intermediate layer. The placement of the third material layer creates a second bandgap and a third bandgap, the sum of which equals the first bandgap. This divides the numerically large first bandgap into two smaller bandgap layers. This helps reduce the bandgap span at the interface, mitigating the weakened electron or hole transport capacity caused by excessively large bandgap spans, and improving conductivity.

[0077] In step S103, multiple sets of simulation working condition parameters are set.

[0078] Each set of simulation operating condition parameters includes: the temperature, voltage, and frequency of the heterojunction solar cell.

[0079] In this embodiment, each set of simulation operating condition parameters for the heterojunction solar cell can be set in the simulation software. For example, in the simulation software, operating points can be set, and each operating point is a set of simulation conditions, which includes multiple parameters.

[0080] In step S104, for each set of simulation operating condition parameters, the simulation operating condition parameters are used to perform simulation calculations on the structure of the first heterojunction and the structure of the second heterojunction, respectively obtaining the first simulation result and the second simulation result reflecting the conductivity.

[0081] In this embodiment, the simulation results may include electron concentration and / or current density. Electron concentration reflects conductivity; the higher the electron concentration, the greater the conductivity. Current density also reflects conductivity; the higher the current density, the greater the conductivity. Both electron concentration and current density can be used simultaneously. An increase in both electron concentration and current density indicates an improvement in conductivity.

[0082] In step S105, the first simulation result and the second simulation result are compared to obtain a comparison result.

[0083] In this embodiment, the amplitude of the first simulation result and the amplitude of the second simulation result are compared.

[0084] In one embodiment, the first simulation result can be a first electron concentration, and the second simulation result can be a second electron concentration. The magnitudes of the first electron concentration and the second electron concentration are compared.

[0085] In one embodiment, the first simulation result can be a first current density, and the second simulation result can be a second current density. The magnitudes of the first current density and the second current density are compared.

[0086] Among them, when both the first current density and the second current density are greater than zero, the amplitude of the current density is greater than zero and equal to the current density value.

[0087] When both the first and second current densities are less than zero, the current density value is less than zero, the amplitude of the current density is greater than zero, and equal to the absolute value of the current density.

[0088] In one embodiment, the first simulation result can be a first electron concentration and a first current density, and the second simulation result can be a second electron concentration and a second current density. The first electron concentration and the second electron concentration are compared, and the first current density and the second current density are also compared.

[0089] In step S106, within a predetermined interval of the horizontal coordinate, the number of second simulation results whose amplitudes are greater than the amplitudes of the first simulation results corresponding to the horizontal coordinate variables are counted.

[0090] In this embodiment, when the simulation result is electron concentration, the horizontal axis variable is distance and the vertical axis is electron concentration; the predetermined horizontal axis interval can be an interval centered on the adjacent interface position of the two materials, and the interval size can be flexibly set.

[0091] When the simulation result is current density, the horizontal axis variable is voltage and the vertical axis is current density; the predetermined range of the horizontal axis can be a voltage range, and the size of the voltage range can be flexibly set.

[0092] In this embodiment, the amplitudes of the first current density and the second current density are compared. If the amplitude of the second current density is greater than that of the first current density, a count is recorded; if the amplitude of the second current density is less than or equal to that of the first current density, no count is recorded. After multiple simulations, the final count results are statistically analyzed.

[0093] In step S107, if the quantity is greater than a predetermined quantity threshold, it is determined that the conductivity of the second heterojunction structure is greater than the conductivity of the first heterojunction structure.

[0094] The aforementioned quantity threshold can be flexibly set, and this application does not impose any limitations. The purpose of setting the quantity threshold is to reduce misjudgments caused by determining the conductivity of two structures based on only a single comparison result, while also avoiding the waste of computational resources due to too many comparisons.

[0095] The technical solution of this application improves the structure of the first heterojunction by placing a third material layer between the first and second material layers to reduce the change in the first bandgap between the first and second material layers, thereby significantly improving the conductivity of the solar cell. Simulations can determine the effectiveness of this improvement, which is beneficial for improving the efficiency of solar cell design and for designing solar cells with enhanced conductivity.

[0096] In some embodiments, the first simulation result is a first electron concentration and / or a first current density; the second simulation result is a second electron concentration and / or a second current density.

[0097] To facilitate observation of the results, the method may further include the following step: generating a first electron concentration distribution curve based on the correspondence between multiple first electron concentrations and positions. Here, position refers to the surrounding region of the interface between two adjacent materials, expressed in μm. In the above coordinate system, the horizontal axis represents distance, and the vertical axis represents electron concentration.

[0098] Based on the correspondence between multiple second electron concentrations and positions, a second electron concentration distribution curve is generated.

[0099] Based on the correspondence between multiple first currents and voltages, a first voltage-current density curve is generated.

[0100] Based on the correspondence between multiple second currents and voltages, a second voltage-current density curve is generated.

[0101] Using the aforementioned two-dimensional curves facilitates the observation of results and greatly improves user efficiency.

[0102] In step S105, the first simulation result and the second simulation result are compared, including:

[0103] In some embodiments, the first voltage-current density curve and the second voltage-current density curve are compared in the same first coordinate system, comparing the first current density and the second current density corresponding to the same voltage value. In this embodiment, the two voltage-current density curves can be compared in the same voltage-current coordinate system, which facilitates observation.

[0104] In the voltage-current density coordinate system, within a predetermined horizontal axis range, if the amplitude of the current density in the second voltage-current density curve is greater than the amplitude of the current density in the first voltage-current density curve, then it is determined that the conductivity of the second heterojunction structure is greater than the conductivity of the first heterojunction structure.

[0105] In some embodiments, the first electron concentration distribution curve and the second electron concentration distribution curve are compared in the same second coordinate system, comparing the first electron concentration and the second electron concentration corresponding to the same position. In this embodiment, the two electron concentration distribution curves can be compared in the same coordinate system of electron concentration and position. Because they are in the same coordinate system, the size relationship can be reflected as a visual vertical relationship, which is clear at a glance and easy to observe.

[0106] In the coordinate system of electron concentration and position, within a predetermined horizontal axis range, if the electron concentration in the second electron concentration distribution curve is greater than the electron concentration in the first electron concentration distribution curve, or simply put, the second electron concentration distribution curve is located above the first electron concentration distribution curve, then the conductivity of the second heterojunction structure is determined to be greater than the conductivity of the first heterojunction structure. The predetermined horizontal axis range is the interval centered on the interface position coordinates.

[0107] In some embodiments, the first voltage-current density curve and the second voltage-current density curve are compared in the same first coordinate system, and the first current density and the second current density corresponding to the same voltage value are compared.

[0108] Furthermore, the first electron concentration distribution curve and the second electron concentration distribution curve are compared in the same second coordinate system to compare the first electron concentration and the second electron concentration corresponding to the same position.

[0109] In this embodiment, both the voltage and current density curves and the electron concentration curves described above are used for judgment.

[0110] One condition is that, within a predetermined horizontal axis range in the voltage-current density coordinate system, the amplitude of the current in the second voltage-current density curve is greater than the amplitude of the current in the first voltage-current density curve.

[0111] Another condition is that, within a predetermined horizontal axis range in the coordinate system of electron concentration and position, the electron concentration in the second electron concentration distribution curve is greater than the electron concentration in the first electron concentration distribution curve, or, simply put, the second electron concentration distribution curve is located above the first electron concentration distribution curve.

[0112] If both of the above conditions are met, then the conductivity of the second heterojunction structure is determined to be greater than that of the first heterojunction structure.

[0113] In some embodiments, see Appendix Figure 5 In this embodiment, the second material is N-type conductive; the intermediate layer is also N-type conductive. Before the third material layer is applied, the first bandgap of the first heterojunction structure is 0.6 eV, which is a high bandgap, hindering current transport at the interface and resulting in a low short-circuit current density J of the battery. SC Significantly reduced, only 1 In this case, red represents the current curve, and the battery's short-circuit current density J. SC Only 1 (Green circle in the image).

[0114] The structure of the first heterojunction described above is improved by adding a third material layer at the interface of the heterojunction solar cell, which can also be referred to as an intermediate layer in the following embodiments. The thickness of the third material layer is 0.05 μm. The short-circuit current density J, originally hindered by a high bandgap of 0.6 eV, is reduced. SC It has returned to saturation. Due to the intermediate layer, the original 0.6 eV high-conductivity band decomposed into a 0.3 eV band 1 and a 0.3 eV band 2, causing the minimum electron concentration at the interface to decrease from less than... The magnitude increased to The minimum electron concentration increased by 10,000 times, and correspondingly, the short-circuit current density J... SC From 1 Increased to a saturation value of 38 Short-circuit current density J SC Performance was restored. With the introduction of the intermediate layer, the blue line represents the current curve, and the short-circuit current density J... SC Restored to saturation value of 38 (The orange circle in the image indicates this).

[0115] In some embodiments, see Appendix Figure 6 The image shows a comparison of electron concentration distribution curves; the blue line represents the electron concentration distribution at the interface without an intermediate layer. In this case, without an intermediate layer, the original high-bandwidth order is 0.6 eV.

[0116] The red line represents the electron concentration distribution after an intermediate layer is set at the interface.

[0117] The horizontal axis x represents the position; where x=1um is the original interface and x=1.0um-1.05um is the introduced N-type intermediate layer.

[0118] In certain intervals of the horizontal axis, such as the interval [0.5-1] and the interval [1-1.05], the red line is above the blue line. That is, for the same horizontal axis, the electron concentration corresponding to the red line is greater than that of the blue line. It can be seen that setting up the intermediate layer significantly improves the current transport capability.

[0119] By setting an intermediate layer at the interface, the original excessively high band structure is decomposed into two band structures, band structure 1 and band structure 2. For example, band structure 1 is the interface between the original P-type layer of the first material and the introduced intermediate layer. The performance is extremely poor, with the second-order layer being the interface between the introduced intermediate layer and the original N-type layer of the second material. The energy difference indicates that the sum of band order 1 and band order 2 equals the original band order. This results in a smoother band structure near the interface, mitigating the sharp decrease in electron concentration at the interface and promoting an increase in current in heterojunction solar cells with higher band order structures.

[0120] In some embodiments, the difference between the second band level and the third band level is less than a predetermined band level difference threshold.

[0121] In this embodiment, the predetermined band difference threshold can be flexibly set. The second band and the third band should be similar, and the difference should not be too large. Controlling the difference between the second band and the third band to be less than the predetermined band difference threshold can improve the short-circuit current density. SC .

[0122] See appendix Figure 7 The graph shown represents the variation of short-circuit current density with band order. The horizontal axis represents band order 1, and the vertical axis represents the short-circuit current density J. SC As the height of the horizontal axis band 1 increases, the short-circuit current density J... SC It gradually increases from zero; in the intermediate region, the short-circuit current density J SC It tends to be constant; in the later stage, the short-circuit current density J SC It decreases linearly.

[0123] Here, 0.6 eV represents the value of the first bandgap before structural improvements. The semiconductor type of the intermediate layer can be N-type.

[0124] Short-circuit current density J SC The preferred range for the horizontal axis is approximately 0.15-0.45 eV, which tends towards a constant intermediate region. This range represents the variation range of band step 1, since the sum of band step 1 and band step 2 is a fixed value, which can be set to 0.6 eV. Because the sum of band step 1 and band step 2 represents the original total band step, when the sub-band step 1 increases, the sub-band step 2 decreases accordingly. Therefore, the variation range of band step 1 can be used to deduce the variation range of band step 2, meaning the preferred variation range for band step 2 is also 0.15-0.45 eV. Furthermore, it can be deduced that the difference between band step 1 and band step 2 is 0.3 eV. In other words, when the difference between band step 1 and band step 2 is below 0.3 eV, the short-circuit current density J... SC It tends to be constant. In this embodiment, the predetermined band difference threshold mentioned above can be set to 0.3 eV.

[0125] In some embodiments, both the second band order and the third band order are less than a predetermined band order threshold.

[0126] In this embodiment, the aforementioned band-level threshold can also be called the upper band-level threshold. The band-level threshold can be flexibly set, for example, to 0.45 eV or 0.4 eV. The smaller the band level, the greater the current carrying capacity. The second band level and the third band level are both smaller than the predetermined band-level threshold, which is beneficial for improving the current carrying capacity.

[0127] In some embodiments, the above method may further include the following steps:

[0128] Determine the absolute value of the difference between the second simulation result and the first simulation result;

[0129] If the amplitude of the first simulation result is greater than the amplitude of the second simulation result, or the absolute value of the difference between the simulation results is less than the simulation result difference threshold, then the second band level and the third band level are adjusted to control the difference between the second band level and the third band level to be less than a predetermined band level difference threshold; and / or, the thickness of the third material layer is increased.

[0130] The following explanation uses the simulation results with electron concentration as an example. When the simulation results are represented by electron concentration distribution curves, the ideal simulation effect is that the electron concentration in the second electron concentration distribution curve is significantly different from that in the first electron concentration distribution curve, the difference between the second electron concentration distribution curve and the first electron concentration distribution curve is obvious, and the second electron concentration distribution curve is above the first electron concentration distribution curve.

[0131] Conversely, unsatisfactory simulation results manifest in the following two forms.

[0132] One manifestation of this is that the electron concentration in the second electron concentration curve is lower than the electron concentration in the first electron concentration curve. That is, the second electron concentration curve is below the first electron concentration curve.

[0133] Another manifestation is that although the second electron concentration curve is above the first electron concentration curve, the difference between the electron concentration in the second electron concentration curve and the electron concentration in the first electron concentration curve is less than a predetermined electron concentration difference threshold. In other words, the second electron concentration curve and the first electron concentration curve are very close together, almost touching, and the difference is not obvious. This is also a situation where the simulation effect is not ideal.

[0134] The predetermined electron concentration difference threshold can be flexibly set.

[0135] To address the issue of unsatisfactory simulation results, this application proposes the following three solutions.

[0136] The first approach involves controlling the difference between the second band level and the third band level to be less than a predetermined band level difference threshold.

[0137] As described above, a relatively stable short-circuit current density can be obtained when the difference between the second and third band levels is less than a predetermined band level difference threshold. Therefore, the difference between the second and third band levels can be controlled to be less than the predetermined band level difference threshold. By setting a suitable band level difference threshold, a relatively stable short-circuit current density can be obtained.

[0138] The second approach is to increase the thickness of the third material layer.

[0139] In this embodiment, increasing the thickness of the third material layer can improve current transport capability and increase electron concentration. To demonstrate that increasing the thickness of the third material layer can increase electron concentration and short-circuit current density, simulations can be performed to verify the relationship between the thickness of the third material layer and the short-circuit current density.

[0140] See appendix Figure 8 The graph shows the relationship between the thickness of the intermediate layer and the short-circuit current density. As the thickness of the intermediate layer increases, the short-circuit current density increases linearly. During the process of increasing the thickness of the intermediate layer from 0.02 μm to 0.08 μm, the short-circuit current density increases from 15.00 μm. Increased to 35.00 above.

[0141] In some embodiments, in order to generate the relationship curve between the thickness of the intermediate layer and the short-circuit current density, the above method may further include the following steps:

[0142] The thickness of the third material layer is increased by a predetermined step size to obtain a sequence of the thicknesses of the third material layer.

[0143] In this embodiment, the predetermined step size can be flexibly set, for example, to 0.1 μm. In this embodiment, all other parameters remain unchanged, only the thickness of the updated third material layer is changed to obtain a structure of multiple updated second heterojunctions.

[0144] The short-circuit current density value of the output of the second heterojunction structure corresponding to each third material layer is calculated to obtain the short-circuit current density sequence.

[0145] In this embodiment, after obtaining the updated second heterojunction structure described above, the heterojunction solar cell of each updated second heterojunction structure can be simulated sequentially to obtain multiple short-circuit current densities.

[0146] A two-dimensional curve of the thickness of the third material layer versus the short-circuit current density is generated based on the sequence of the thickness of the third material layer and the sequence of the short-circuit current density.

[0147] In this embodiment, the correspondence between each short-circuit current density and the thickness of each of the aforementioned third material layers can be determined first. Based on the correspondence between each short-circuit current density and the thickness of each of the aforementioned third material layers, a curve showing the relationship between the thickness of the intermediate layer and the short-circuit current density is generated.

[0148] The third approach involves controlling the difference between the second and third band steps to be less than a predetermined band step difference threshold, and increasing the thickness of the third material layer.

[0149] In this embodiment, if the difference between the second band level and the third band level is less than a predetermined band level difference threshold, the simulation effect is still not ideal. On this basis, the thickness of the third material layer can be further increased to increase the short-circuit current density, thereby improving the simulation effect.

[0150] Specifically, based on a large amount of experimental data collected in advance, the thickness of the aforementioned third material layer can be increased in predetermined steps, thereby gradually increasing the short-circuit current density.

[0151] In some embodiments, each set of simulation operating condition parameters includes: the temperature, voltage, and frequency of the heterojunction solar cell.

[0152] The setting of multiple sets of simulation operating condition parameters includes: keeping the temperature and frequency of the heterojunction solar cell constant in each set of simulation operating condition parameters; applying a voltage to the heterojunction solar cell, with the voltage gradually increasing from a first voltage to a second voltage in predetermined voltage steps, thus obtaining multiple sets of simulation operating condition parameters. In the following description, for simplicity, each set of simulation operating condition parameters can also be referred to as each operating point.

[0153] In this embodiment, when setting multiple sets of simulation operating condition parameters, several parameters can be kept constant while only one parameter is adjusted. For example, the temperature and frequency can be kept constant while only the voltage is adjusted, thus obtaining multiple sets of simulation operating condition parameters.

[0154] When adjusting the voltage, the first voltage of the first group and the second voltage of the last group can be determined first. A predetermined voltage step size is then determined based on the first and second voltages. For example, the difference between the first and second voltages can be divided by the predetermined number of steps to obtain each step size. For instance, the first voltage could be 0.0V, the second voltage could be 0.8V, and the voltage step size could be 0.1V.

[0155] While keeping the temperature and frequency constant, a voltage is applied to the heterojunction solar cell, with the voltage gradually increasing from a first voltage to a second voltage in predetermined voltage steps, traversing the voltage at each operating point.

[0156] At each operating point, the current density at that operating point is calculated based on the voltage at that operating point.

[0157] The first voltage-current curve is generated based on the voltage and current density at each operating point.

[0158] In the above embodiment, the voltage sequence is a voltage sequence from 0 to 0.8 with an interval of 0.1. The corresponding current density can be calculated based on each voltage, thereby obtaining a current density sequence. A first voltage-current curve is generated based on the above voltage sequence and current density sequence.

[0159] Furthermore, the corresponding relationship between electron concentration and position can be obtained from simulation calculations to generate the first electron concentration distribution curve.

[0160] Similarly, the same method described above is used to calculate the second heterojunction, and the second voltage-current curve and the second electron concentration distribution curve can be obtained.

[0161] See appendix Figure 9 Improving the structure of the first heterojunction by providing a third material layer between the first material layer 01 and the second material layer 02 may further include the following steps:

[0162] The second material layer 02 is divided into a second material first layer 021 and a second material second layer 022.

[0163] The second material first layer 021 is adjacent to the first material layer 01.

[0164] Modify the electrical parameters of the first layer 021 of the second material to transform the first layer 021 of the second material into the third material layer.

[0165] See appendix Figure 10 The modification of the electrical parameters of the first layer of the second material described above may further include the following steps:

[0166] The electron affinity (ea) in the first layer of the second material is modified, and the first electron affinity ea1 of the first layer of the second material is modified to the second electron affinity ea2.

[0167] Electron affinity is used to represent the difference between the conduction band bottom and the vacuum level.

[0168] The second electron affinity ea2 is between the first electron affinity ea1 and the electron affinity ea3 of the first material layer.

[0169] The bottom of the conductive strip is the second material layer; The bottom of the first material layer is the conductive strip; , which is the vacuum energy level.

[0170] The first electron affinity energy ea1 of the first layer of the second material mentioned above represents the electron affinity energy of the second material, and is calculated using the vacuum energy level formula. Subtract the conductor base of the second material layer .

[0171] The electron affinity energy ea3 of the first material layer mentioned above is calculated using the vacuum energy level formula. Subtract the conductor base of the first material layer .

[0172] In some embodiments, the band gap in the first layer of the second material is modified accordingly based on the first electron affinity and the second electron affinity, so as to keep the valence band top in the first layer of the second material unchanged.

[0173] In this embodiment, the band gap in the first layer of the second material is modified accordingly based on the first electron affinity and the second electron affinity to keep the valence band top in the first layer of the second material unchanged. This can further include the following steps:

[0174] The difference between the second electron affinity and the first electron affinity described above is determined, hereinafter referred to as the electron affinity difference.

[0175] Determine the first band gap in the first layer of the second material.

[0176] The modified second bandgap is determined based on the first bandgap and the electron affinity difference mentioned above.

[0177] In this embodiment, the first bandgap and the electron affinity difference can be subtracted, that is, the first bandgap is subtracted from the electron affinity difference to obtain the modified second bandgap.

[0178] The following explains the logical reasoning behind the above calculations. Since the band gap of any material is equal to the difference between the conduction band bottom and the valence band top energy level, to keep the position of the valence band top energy level constant, the position of the conduction band bottom energy level is positively correlated with the band gap. Because the conduction band bottom energy level is a fixed vacuum energy level minus the electron affinity, the position of the conduction band bottom energy level is negatively correlated with the electron affinity. Based on the above relationship, it can be deduced that the band gap is negatively correlated with the electron affinity. That is, if the second electron affinity is greater than the first electron affinity, the second band gap should be smaller than the first band gap. The direction of change in the band gap is opposite to the direction of change in the electron affinity, but the absolute value of the change is the same.

[0179] In some embodiments, the first material in the first material layer may be copper indium gallium selenide (CIGS); and the second material in the second material layer may be cadmium sulfide (CdS).

[0180] In the above embodiments, the second material has an N-type conductivity, and the intermediate layer also has an N-type conductivity. In the following embodiments, the second material has a P-type conductivity, and the intermediate layer also has a P-type conductivity. Simulations further verify that the method described above can be applied to various types of materials.

[0181] See appendix Figure 10-13 The graphs shown are simulation results of various short-circuit current densities when the conductivity type of the second material is P-type and the conductivity type of the intermediate layer is P-type.

[0182] See appendix Figure 10 A P-type interlayer with a thickness of 0.05 μm was introduced at the interface of the heterojunction solar cell. After dividing the original 0.6 eV high-bandwidth step into two 0.3 eV bandwidth steps, the short-circuit current density of the cell was restored. The green line represents the voltage-current curve when the 0.6 eV high-bandwidth step was not introduced, and the short-circuit current density of the cell was only 1. It is evident that the high-bandgap structure hinders current output; the blue line represents the voltage-current curve after introducing the P-type intermediate layer, where the short-circuit current density recovers to the saturation value of 38. .

[0183] See appendix Figure 11 The x-axis represents the original interface at 1µm, and the x-axis range of 0.95µm-1.0µm represents the added intermediate layer. As shown in the green circle in the drawing, before and after adding the intermediate layer, the lowest electron concentration at the interface changes from less than... The magnitude increased to The minimum electron concentration has increased by more than 1,000 times.

[0184] See appendix Figure 12 After setting a P-type intermediate layer, the short-circuit current density gradually increases with the increase of the band height 1.

[0185] It is evident that to significantly improve the short-circuit current density, it is necessary to select the intermediate layer appropriately. When dividing the high-band level into two sub-band levels, the difference between the two sub-band levels should be controlled to avoid the situation where band level 1 or band level 2 is too large.

[0186] See appendix Figure 13The diagram shows another relationship between interlayer thickness and short-circuit current density. In this case, band 1 is 0.1 eV and band 2 is 0.5 eV. As the interlayer thickness increases, the short-circuit current density gradually increases, but it does not reach a saturation value. This indicates that even with a P-type interlayer, increasing the thickness can still improve the short-circuit current density. This is the same as the N-type interlayer example mentioned earlier. The difference lies in the fact that, with a P-type interlayer, increasing the thickness to improve current density is slightly less effective than with an N-type interlayer.

[0187] In this application's technical solution, material A has excellent light absorption properties and is suitable as a light absorption layer, corresponding to the first material layer mentioned above; material B has good electron transport properties and is suitable as a buffer layer, corresponding to the second material layer mentioned above. At the interface between materials A and B, if the conduction band level is high, the high conduction band level will cause a large concentration difference on both sides of the interface, resulting in extremely low electron concentration at the interface, which restricts current transmission and is detrimental to current output. In this case, an intermediate layer can be introduced at the interface. This intermediate layer can divide the conduction band level at the interface of materials A and B into two band level steps, thereby reducing the concentration difference at the interface, avoiding the appearance of extremely low electron concentration regions, preventing restricted current transmission, and improving current output.

[0188] The aforementioned intermediate layer can be of the same conductivity type as the light-absorbing layer of material A, or it can be of the same conductivity type as material B. However, the intermediate layer material must be selected appropriately so that neither of the two band divisions in the band structure after the original band division is separated by the intermediate layer is too high; for example, neither band division should exceed 0.45 eV. If the introduced intermediate layer band structure is still not ideal enough to restore the short-circuit current density to its saturation value, the thickness of the intermediate layer can be further increased, which can further improve the short-circuit current density. However, increasing the thickness of the absorption layer is not as effective as properly distributing the band divisions, and can be considered a secondary optimization.

[0189] The above embodiments are described with electrons as the conductive medium. Similarly, the above methods are also applicable when the conductive medium is holes, and both can improve conductivity.

[0190] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of this disclosure. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the following claims.

[0191] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. A simulation method for improving the conductivity at the interface of a heterojunction solar cell, characterized in that, include: The structure of the first heterojunction of the heterojunction solar cell includes an adjacent first material layer and a second material layer. The band step between the first material layer and the second material layer is a first band step, which is greater than a predetermined first band step threshold. The structure of the first heterojunction is improved by setting a third material layer between the first material layer and the second material layer to obtain the structure of the second heterojunction. In the structure of the second heterojunction, the band step between the third material layer and the first material layer is the second band step; The band step between the third material layer and the second material layer is the third band step; the sum of the second band step and the third band step is equal to the first band step; Set multiple sets of simulation operating condition parameters; For each set of simulation operating condition parameters, the structure of the first heterojunction and the structure of the second heterojunction are simulated and calculated using the simulation operating condition parameters, and the first simulation result and the second simulation result reflecting the conductivity are obtained respectively. Compare the first simulation result with the second simulation result; Within a predetermined range of horizontal coordinates, count the number of second simulation results whose amplitudes are greater than the amplitudes of the first simulation results corresponding to the horizontal coordinate variables. If the quantity is greater than a predetermined threshold, it is determined that the conductivity of the second heterojunction structure is greater than that of the first heterojunction structure.

2. The simulation method for improving the conductivity at the heterojunction solar cell interface according to claim 1, characterized in that, The first simulation result is the first electron concentration and / or the first current density; The second simulation result is the second electron concentration, and / or, the second current density; The first simulation result and the second simulation result are compared, including: The first voltage-current density curve and the second voltage-current density curve are compared in the same first coordinate system, and the first current density and the second current density corresponding to the same voltage value are compared respectively. And / or, The first electron concentration distribution curve and the second electron concentration distribution curve are compared in the same second coordinate system, and the first electron concentration and the second electron concentration corresponding to the same position are compared respectively.

3. The simulation method for improving the conductivity at the heterojunction solar cell interface according to claim 1, characterized in that, The difference between the second band order and the third band order is less than a predetermined band order difference threshold. Both the second and third band orders are less than the predetermined band order threshold.

4. The simulation method for improving the conductivity at the heterojunction solar cell interface according to claim 2, characterized in that, The method further includes: determining the absolute value of the simulation result difference between the second simulation result and the first simulation result; If the amplitude of the first simulation result is greater than the amplitude of the second simulation result, or the absolute value of the difference between the simulation results is less than the simulation result difference threshold, adjust the second band level and the third band level to control the difference between the second band level and the third band level to be less than a predetermined band level difference threshold; and / or increase the thickness of the third material layer.

5. The simulation method for improving the conductivity at the heterojunction solar cell interface according to claim 1, characterized in that, The method further includes: The thickness of the third material layer is increased by a predetermined step size to obtain a sequence of the thicknesses of the third material layer. Calculate the output short-circuit current density value of the second heterojunction structure corresponding to each third material layer to obtain the short-circuit current density sequence; A two-dimensional curve of the thickness of the third material layer versus the short-circuit current density is generated based on the sequence of the thickness of the third material layer and the sequence of the short-circuit current density.

6. The simulation method for improving current transport capability at the heterojunction solar cell interface according to claim 1, characterized in that, Each set of simulation operating condition parameters includes: the temperature, voltage, and frequency of the heterojunction solar cell; The setting of multiple sets of simulation operating condition parameters includes: keeping the temperature and frequency of the heterojunction solar cell constant in each set of simulation operating condition parameters, applying a voltage to the heterojunction solar cell, and gradually increasing the voltage from a first voltage to a second voltage in a predetermined voltage step, thereby obtaining multiple sets of simulation operating condition parameters.

7. The simulation method for improving current transport capability at the heterojunction solar cell interface according to claim 1, characterized in that, The structure of the first heterojunction is improved by providing a third material layer between the first material layer and the second material layer, including: The second material layer is divided into a first layer of second material and a second layer of second material; The first layer of the second material is adjacent to the first material layer; Modify the electrical parameters of the first layer of the second material to transform the first layer of the second material into the third material layer.

8. The simulation method for improving current transport capability at the heterojunction solar cell interface according to claim 7, characterized in that, Modifying the electrical parameters of the first layer of the second material includes: The electron affinity in the first layer of the second material is modified, and the first electron affinity in the first layer of the second material is modified to the second electron affinity; The second electron affinity is between the first electron affinity and the electron affinity of the first material layer.

9. The simulation method for improving current transport capability at the heterojunction solar cell interface according to claim 8, characterized in that, Modifying the electrical parameters of the first layer of the second material also includes: Based on the first electron affinity and the second electron affinity, the band gap in the first layer of the second material is modified accordingly to keep the valence band top in the first layer of the second material unchanged.

10. The simulation method for improving current transport capability at the heterojunction solar cell interface according to any one of claims 1 to 9, characterized in that, The first material in the first material layer is copper indium gallium selenide; the second material in the second material layer is cadmium sulfide.

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