Local contact dielectric layer, perovskite solar cell and preparation method thereof

Abstract

The invention discloses a local contact dielectric layer, a perovskite solar cell and a preparation method thereof, and relates to the field of solar cells, the local contact dielectric layer comprises a trapezoid cross section, and the height of the trapezoid is 10-200nm; the lower bottom of the trapezoid is connected with the electron transport layer, and the rest parts are embedded into the perovskite absorption layer. The trapezoidal insulating passivation material is arranged between the perovskite layer and the electron transport layer, so that the light absorption rate of the perovskite layer is effectively improved, carriers form a special charge transport structure at a local passivation structure, the effect of efficiently passivating an interface between the perovskite layer and the electron transport layer is achieved, and the efficiency of the perovskite solar cell is improved. Therefore, interface recombination is reduced, transmission of carriers between the perovskite layer and the electron transmission layer is not affected, and balance between high open-circuit voltage and high fill factors is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, in particular to a local contact dielectric layer, a perovskite solar cell and a preparation method thereof. Background Art

[0002] Perovskite solar cells have undoubtedly attracted great attention in the photovoltaic field. In the past 14 years, the photoelectric conversion efficiency of single-junction perovskite solar cells has rapidly increased to 26.1%, just one step away from the highest record efficiency of 27.09% for traditional silicon solar cells. However, this value is still significantly lower than the Shockley-Queisser limit efficiency of 33% for single-junction perovskite cells, which is mainly attributed to the inherent photoelectric loss of perovskite solar cells.

[0003] On the one hand, the optical loss of perovskite solar cells mainly comes from the reflection of sunlight on the device surface and the transmission generated by passing through the device. On the other hand, the factors that lead to the electrical loss of perovskite solar cells can be mainly divided into bulk recombination and surface / interface recombination. For optical loss, researchers have enhanced the device's ability to absorb light through light-trapping structures such as photonic crystals and pyramid structures. In terms of bulk recombination, researchers have effectively alleviated it through different crystallization optimization strategies and bulk passivation techniques, significantly increasing the diffusion length to 8.76µm and the bulk recombination lifetime to 6.0µs. These significant values ​​indicate that the electrical loss caused by bulk recombination is negligible. In this case, surface / interface recombination becomes a more important constraint on device performance, especially in terms of open-circuit voltage. To address this problem, many surface / interface passivation schemes have been proposed, such as organic molecular layers, polymers, two-dimensional perovskites, and ultrathin dielectric oxide layers, which are used to modify the surface / interface or as a passivation layer to significantly reduce the open-circuit voltage loss of perovskite solar cells.

[0004] Unfortunately, many passivation strategies cannot make full use of the light source, resulting in a large amount of light energy being wasted and unable to improve the photoelectric efficiency from the root. At the same time, some passivation layers exhibit poor conductivity, which means that achieving optimal passivation quality is usually accompanied by an increase in series resistance, resulting in a decrease in fill factor. The trade-off between passivation quality and series resistance has become a major challenge in improving the performance of perovskite solar cells. Therefore, discovering a structural design that simultaneously minimizes surface / interface recombination and contact resistance is crucial to overcoming the trade-off between open circuit voltage and fill factor. Summary of the invention

[0005] In view of the above problems existing in the prior art, the present invention is proposed.

[0006] Therefore, the problem to be solved by the present invention is how to enhance the absorption capacity of the perovskite layer and improve the utilization rate of the light source. Secondly, solve the recombination problem at the interface and achieve an efficient passivation effect, so that the battery has the characteristics of high light absorption coefficient, high photogenerated carrier separation efficiency, low defect density, and high photoelectric conversion efficiency.

[0007] In order to solve the above technical problems, in the first aspect, the present invention provides the following technical solutions: a local contact dielectric layer, comprising: the cross-sectional shape of the local contact dielectric layer is a trapezoid, the height of the trapezoid is 10~200nm; the bottom of the trapezoid is connected to the electron transport layer, and the remaining part is embedded in the perovskite absorption layer.

[0008] As a preferred solution of the local contact dielectric layer of the present invention, the local contact dielectric layer is arranged in an array at the interface between the electron transport layer and the perovskite absorption layer, with a period of 100-400 nm.

[0009] As a preferred solution of the local contact dielectric layer of the present invention, the lower bottom length of the local contact dielectric layer is 0.1-450 nm, and the upper bottom length is 1-450 nm.

[0010] As a preferred solution of the local contact dielectric layer of the present invention, the material of the local contact dielectric layer is metal oxide.

[0011] As a preferred solution of the local contact dielectric layer of the present invention, the duty ratio of the local contact dielectric layer is 1-90%.

[0012] As a preferred solution of the local contact dielectric layer of the present invention, the height of the local contact dielectric layer is 120 nm, the period is 320 nm, the ratio of the upper base to the lower base is 0.2, and the duty cycle is 90%.

[0013] In a second aspect, the present invention further provides a perovskite solar cell, which includes a first electrode layer, an electron transport layer, the above-mentioned local contact medium layer, a perovskite absorption layer, a hole transport layer and a second electrode layer stacked in sequence on a substrate.

[0014] As a preferred solution of the perovskite solar cell of the present invention, the band gap of the perovskite absorption layer is 1.53 eV, and the material of the electron transport layer is SnO2.

[0015] In a third aspect, the present invention also provides a method for preparing a perovskite solar cell, the method comprising forming a first electrode layer on a substrate; forming an electron transport layer on the first electrode layer; forming a local contact dielectric layer on the electron transport layer; forming a perovskite absorption layer on the local contact dielectric layer; forming a hole transport layer on the perovskite absorption layer; and forming a second electrode layer on the hole transport layer.

[0016] As a preferred solution of the method for preparing the perovskite solar cell of the present invention, the height of the local contact dielectric layer is 120 nm, the period is 320 nm, the ratio of the upper base to the lower base is 0.2, and the duty cycle is 90%.

[0017] The beneficial effects of the present invention are: 1. The present invention adopts a strategy of using a local contact dielectric layer between the perovskite layer and the electron transport layer, which effectively reduces the reflection in the short-wave band, enhances the light absorption of the perovskite layer, and significantly improves the photocurrent of the perovskite solar cell.

[0018] 2. The present invention uses a local contact passivation structure, and carriers form a new charge transfer mode at the local contact passivation structure, avoiding the disadvantages of strict requirements on passivation layer materials and preparation of passivation layers when passivating interface defects, achieving the effect of efficient passivation of the interface between the perovskite layer and the electron transport layer, reducing interface recombination, and at the same time not affecting the transmission of carriers between the perovskite layer and the electron transport layer, achieving a balance between high open circuit voltage and high fill factor.

[0019] 3. The present invention utilizes a local passivation structure to not only passivate the interface defects between the perovskite layer and the electron transport layer, reduce non-radiative recombination, and increase the open circuit voltage, but also because the local passivation structure surface carries positive interface charges, which will have a huge impact on the electric field in the perovskite layer, thereby achieving a dual improvement in passivation and transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 This is a structural diagram of the local contact dielectric layer and perovskite solar cell.

[0022] Figure 2 Corresponding to Table 1, the photogenerated current under different refractive indices when the height, upper and lower side ratio and duty cycle of the local contact dielectric layer 1 are 120 nm, 0.2 and 90% respectively.

[0023] Figure 3 Corresponding to Table 2, the photogenerated current under different duty cycles when the height, upper and lower side ratio and refractive index of the local contact medium layer 1 are 120 nm, 0.2 and 3.1 respectively.

[0024] Figure 4 The absorptivity and reflectivity of solar cell devices with different structures vary with wavelength.

[0025] Figure 5 Corresponding to Table 3, when the upper and lower side ratios, refractive index and duty cycle of the local contact medium layer 1 are 0, 3.1 and 90% respectively, the photocurrents at different heights and periods.

[0026] Figure 6 Corresponding to Table 4, when the upper and lower side ratios, refractive index and duty cycle of the local contact medium layer 1 are 0.2, 3.1 and 90% respectively, the photocurrents at different heights and periods.

[0027] Figure 7 Corresponding to Table 5, when the upper and lower side ratios, refractive index and duty cycle of the local contact medium layer 1 are 0.6, 3.1 and 90% respectively, the photocurrents at different heights and periods.

[0028] Figure 8 Corresponding to Table 6, when the upper and lower side ratios, refractive index and duty cycle of the local contact medium layer 1 are 1, 3.1 and 90% respectively, the photocurrent at different heights and periods.

[0029] Fig. 9 is the photogenerated electric field distribution corresponding to the device at a wavelength of 450nm.

[0030] Fig.10 The relationship between the open circuit voltage and duty cycle of perovskite solar cells under different interface defect densities of the perovskite layer and the electron transport layer.

[0031] Fig.11 The relationship between the filling factor and duty cycle of perovskite solar cells under different interface defect densities of the perovskite layer and the electron transport layer.

[0032] Fig.12 The relationship between the power conversion efficiency and duty cycle of perovskite solar cells under different interface defect densities of the perovskite layer and the electron transport layer.

[0033] Fig.13 This is the relationship between the open circuit voltage and the number density of interface defects under different local contact dielectric layer periods.

[0034] Fig.14 This is the relationship between the filling factor and the number density of interface defects under different local contact dielectric layer periods.

[0035] Fig.15 This is the relationship between the open circuit voltage and the number density of interface defects at different local contact dielectric layer heights.

[0036] Fig.16 This is the relationship between the filling factor and the number density of interface defects at different local contact dielectric layer heights.

[0037] Fig.17 The relationship between the open circuit voltage and the number density of interface defects under different local contact dielectric layer upper and lower edge ratios (α).

[0038] Fig.18 The relationship between the filling factor and the number density of interface defects under different upper and lower edge ratios (α) of the local contact dielectric layer.

[0039] Fig.19 is the relationship between the filling factor and the number density of interface defects under different local contact dielectric layer surface charge density (σ).

[0040] Fig. 20 is the relationship between the open circuit voltage and the number density of interface defects under different local contact dielectric layer surface charge density (σ).

[0041] Fig.21 is the relationship between the power conversion efficiency and the number density of interface defects under different local contact dielectric layer surface charge density (σ).

[0042] Fig. 22 For a planar structure, no interface charge, local contact with the dielectric layer, and a positive interface charge (charge density of 10 12 cm -2 ) in three cases of local passivation dielectric layer, the power conversion efficiency of perovskite solar cells varies with ion concentration.

[0043] Fig.23 for Fig. 22 The fixed ion concentration is 10 16 cm -3 The current-voltage curve corresponding to the perovskite solar cell device.

[0044] Fig.24 Current-voltage and power-voltage curves of the optimal perovskite solar cell device and the planar perovskite solar device.

[0045] In the figure: 1. local contact dielectric layer; 2. electron transport layer; 3. perovskite absorption layer; 4. substrate; 5. first electrode layer; 6. hole transport layer; 7. second electrode layer. DETAILED DESCRIPTION

[0046] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0047] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0048] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it an embodiment that is mutually exclusive with other embodiments, either individually or selectively.

[0049] Reference Figure 1 , which is the first embodiment of the present invention, and this embodiment provides a local contact dielectric layer 1, the shape of the local contact dielectric layer 1 is a trapezoid, and the height of the trapezoid, that is, the local contact dielectric layer 1, is 20~200nm. The local contact dielectric layer 1 is composed of metal oxides and is arranged in an array between the interface of the electron transport layer 2 and the perovskite absorption layer 3. The lower bottom edge of the local contact dielectric layer 1 is in contact with the electron transport layer 2, and the rest of the part is embedded in the perovskite absorption layer 3. The period of the local contact dielectric layer 1 is 100~400nm, the ratio of the upper bottom to the lower bottom is 0.2, and the duty cycle is 1~90%.

[0050] Preferably, the height of the local contact dielectric layer 1 is 120 nm, the period is 100 nm, and the duty cycle is 90%.

[0051] As an optional embodiment, the present invention also provides a perovskite solar cell, which includes a first electrode layer 5, an electron transport layer 2, the above-mentioned local contact medium layer 1, a perovskite absorption layer 3, a hole transport layer 6 and a second electrode layer 7 stacked in sequence on a substrate 4.

[0052] Preferably, the substrate 4 is a glass substrate, and the material of the first electrode layer 5 is a transparent conductive oxide, which is ITO with a thickness of 180 nm. The first electrode layer 5 serves as an electrode of the device.

[0053] Preferably, the material of the electron transport layer 2 is SnO2, and the thickness is 50 nm.

[0054] Preferably, the band gap of the perovskite absorption layer 3 is 1.53 eV and the thickness thereof is 600 nm. The perovskite absorption layer 3 is stacked on the local contact dielectric layer 1 , and simultaneously fills the gaps between the local contact dielectric layers 1 and completely covers the local contact dielectric layer 1 .

[0055] Preferably, the hole transport layer 6 is 2,2',7,7'-tetrakis[N,N-di(methoxyphenyl)amino]-9,9'-spirobifluorene and has a thickness of 150 nm.

[0056] Preferably, the second electrode layer is made of gold and has a thickness of 100 nm, and serves as another electrode of the device.

[0057] It should also be noted that for the selection of the refractive index of the local contact dielectric layer 1, the optical absorption of the perovskite is calculated in turn with an increment of 20 nm when the period of the local contact dielectric layer 1 changes from 100 nm to 400 nm and the refractive index of the local contact dielectric layer 1 changes from 2.5 to 3.5. The specific photogenerated current of the perovskite solar cell is shown in Table 1 below: Table 1: Photogenerated current at different refractive indices when the height, upper and lower side ratio and duty cycle of the local contact dielectric layer 1 are 120nm, 0.2 and 90% respectively.

[0058] ,

[0059] Table 1 continued: , From Table 1 and Figure 2 It can be clearly seen that with the increase of the refractive index of the local contact dielectric layer 1, the photocurrent of the device shows a trend of first increasing and then decreasing. When the local contact dielectric layer 1 is close to 3.1, the optical absorption rate of the perovskite is significantly higher; as the period of the local contact dielectric layer 1 gradually increases, the photocurrent of the device shows a trend of decreasing.

[0060] At this time, it is preliminarily determined that the refractive index of the local contact medium layer 1 is 3.1.

[0061] We continue to calculate different situations where the period of the local contact dielectric layer is 100nm, 320nm, 400nm and the duty cycle is from 0 to 0.9. The optical absorption of the device is shown in Table 2 below: Table 2: Photogenerated current at different duty cycles when the height, upper and lower side ratio and refractive index of the local contact dielectric layer 1 are 120nm, 0.2 and 3.1 respectively.

[0062] ,

[0063] Table 2 continued: , From Table 2 and Figure 3 It can be clearly observed that as the duty cycle of the local contact dielectric layer 1 increases, the photogenerated current of the perovskite solar cell under different periods gradually increases, and is significantly higher than the photogenerated current of the planar structure perovskite cell.

[0064] At this time, it is preliminarily determined that the duty cycle of the local contact dielectric layer is 90%.

[0065] By comparing the absorption spectrum and reflectivity spectrum of the perovskite absorption layer 3 when the period of the local contact dielectric layer 1 is 100nm and 320nm and the duty cycle is 50% and 90%, as shown in Figure 4 It can be seen that the presence of the nanoscale local contact dielectric layer 1 effectively enhances the light absorption of the perovskite absorption layer 3, especially in the short wavelength band. This is because the nanoscale local contact dielectric layer 1 effectively reduces the reflection in the short wavelength band.

[0066] based on Figure 4 , the size of the local contact dielectric layer 1 is further optimized, the refractive index is selected as 3.1, the duty cycle is 90%, and the height of the local contact dielectric layer 1 is calculated from 20nm to 200nm in increments of 20nm, the period is changed from 100 to 400nm, and the upper and lower side ratios are 0 (the local contact dielectric layer 1 is a triangle at this time), 0.2, 0.6 and 1 respectively. The optical absorption of the device is shown in Table 3 below: Table 3: Photogenerated current at different heights and periods when the upper and lower side ratios, refractive index and duty cycle of the local contact dielectric layer 1 are 0, 3.1 and 90% respectively.

[0067] ,

[0068] Table 3 continued: , Table 4: Photogenerated current at different heights and periods when the upper and lower side ratios, refractive index and duty cycle of the local contact dielectric layer 1 are 0.2, 3.1 and 90% respectively.

[0069] ,

[0070] Table 4 continued: , Table 5: Photogenerated current at different heights and periods when the upper and lower side ratios, refractive index and duty cycle of the local contact dielectric layer 1 are 0.6, 3.1 and 90% respectively.

[0071] ,

[0072] Table 5 continued: , Table 6: Photogenerated current at different heights and periods when the upper and lower side ratios, refractive index and duty cycle of the local contact dielectric layer 1 are 1, 3.1 and 90% respectively.

[0073] ,

[0074] Table 6 continued: , Comprehensive Table 3~Table 6 and Figure 5~Figure 8 It can be seen that as the period of the local contact dielectric layer 1 increases, the photogenerated current of the device shows a downward trend; As the height of the local contact dielectric layer 1 increases, the photogenerated current of the device as a whole shows a trend of first increasing and then decreasing.

[0075] By comparing the different top-to-bottom ratios horizontally, it can be clearly seen that as the top-to-bottom ratio increases, the photocurrent of the device shows a downward trend.

[0076] Therefore, the parameters of the local contact medium layer 1 are set to a refractive index of 3.1, a duty cycle of 90%, a top-bottom ratio of 0.2, a period of 320 nm, and a height of 100 nm.

[0077] also, Fig. 9 The light field distribution at an incident wavelength of 450nm is given when the period of the local contact dielectric layer 1 is 100nm and 320nm and the duty cycle is 50% and 90%, indicating that although the volume of the perovskite absorption layer 3 is reduced due to the presence of the local contact dielectric layer 1, the effective light absorption area is expanded. The resonance mode is excited in the area with a period of 320nm and the local contact dielectric layer 1, which enhances the light absorption of the perovskite absorption layer 3.

[0078] In order to further study the local contact dielectric layer in the present invention, the interface defect density between the electron transport layer 2 and the perovskite absorption layer 3 is calculated at different duty ratios, such as Figure 10~Figure 12 The defect density between the electron transport layer 2 and the perovskite absorption layer 3 was selected as 10 9 cm -2 , 10 10 cm -2 , 10 11 cm -2 Three cases are calculated.

[0079] It can be seen that under different interface defect densities, the open circuit voltage increases with the increase of duty cycle. The greater the interface defect density, the greater the increase in open circuit voltage. This is because as the duty cycle increases, the effective interface recombination area decreases, thereby reducing interface non-radiative recombination and increasing the open circuit voltage.

[0080] It is worth noting that under low interface defect conditions, the filling factor shows a downward trend with increasing duty cycle, which can be explained by the increase in carrier transport resistance with increasing duty cycle of the local contact dielectric layer 1. Under high interface defect conditions, the filling factor shows a bidirectional trend of first increasing and then decreasing with duty cycle. This phenomenon can be attributed to the fact that a moderate increase in duty cycle reduces non-radiative recombination, thereby enhancing the filling factor, while a significant increase in duty cycle leads to a significant increase in series resistance, ultimately leading to a decrease in filling factor. This finding emphasizes the complex interaction between the duty cycle of the local contact dielectric layer 1 and the interface defect density. Ultimately, we observed that the device efficiency continued to increase with increasing duty cycle, and this increase was further enhanced at higher interface defects. When the interface defect density is 10 9 cm -2 When the duty cycle increases, the device efficiency tends to saturation.

[0081] In addition, if Figure 13~Figure 18 , a fixed medium trap density at the interface of the electron transport layer 2 / perovskite absorption layer 3 (the interface defect density of the perovskite absorption layer 3 and the electron transport layer 2 interface and the local contact dielectric layer 1 interface are both 10 10 cm -2 ) and the duty cycle is 90%, the stability of the device performance to the size and morphology changes of the nanostructures in the local contact dielectric layer 1 at different passivation levels. The interface defect density at the interface between the perovskite absorption layer 3 and the electron transport layer 2 and the interface of the local contact dielectric layer 1 is 10 10 cm -2 In the case of , the open circuit voltage and fill factor of the planar structure are 1.14 V and 85.26%, respectively. In contrast, when the local contact dielectric layer 1 is not passivated enough (the interface defect density between the perovskite absorber layer 3 and the local contact dielectric layer 1 exceeds 2×10 8 cm -2 ), this structure has no meaning for improving the electrical performance of the device. The device performance is highly dependent on the structural morphology and size of the local contact dielectric layer 1, especially its height, where the smaller the ratio of period, height and upper and lower sides, the better the device performance. When passivation is effective, the device performance is highly robust to the structural period, morphology and size, which greatly facilitates practical manufacturing.

[0082] In view of the typical existence of surface charges in the local contact dielectric layer 1, we have studied in depth the effect of interface charges on the device performance. Figure 19~Figure 21 The relationship between the filling factor, open circuit voltage and device efficiency of perovskite solar cells and the interface defect density between the perovskite absorber layer 3 and the local contact dielectric layer 1 under different interface charge density (σ) and polarity is shown. Here, the interface defect density of the perovskite absorber layer 3 / electron transport layer 2 and the perovskite absorber layer 3 / hole transport layer 6 interface is 1010 cm -2 , the duty cycle of the local contact dielectric layer is 90%. This study reveals the following: 1) Positive interfacial charges usually have a beneficial effect on device performance because they promote the transport of electrons to the electron transport layer. In contrast, negative interfacial charges repel the transport of electrons to the electron transport layer. In addition, the local contact passivation structure has a 10 12 cm -2 When the interfacial charge density is -10 12 cm -2 When the interface charge density is , a potential barrier is formed at the interface between the perovskite absorption layer 3 and the electron transport layer 2, hindering the transfer of electrons.

[0083] 2) Regardless of the polarity, as the interface defect density between the perovskite absorption layer 3 and the local contact dielectric layer 1 increases, the reduction in the interface charge density of the local contact passivation structure will lead to a more serious degradation of device performance.

[0084] 3) At very high charge densities (±10 12 cm -2 ), the change in the interface defect density between the perovskite absorber layer 3 and the local contact dielectric layer 1 has little effect on the device performance, which is due to the physical field passivation caused by the high interface charge. Regardless of the interface trap density, high-density interface charges of any polarity will hinder the approach of carriers of opposite polarity, thereby limiting effective interface recombination.

[0085] In summary, for formal perovskite solar cells, introducing a passivating local contact dielectric layer 1 having a high-density surface positive charge characteristic at the interface between the electron transport layer 2 and the perovskite absorption layer 3 is beneficial to improving device performance.

[0086] In addition, ion migration is an important phenomenon in perovskite solar cells, so the effect of ion migration on the performance of perovskite solar cells with passivated local contact dielectric layer 1 was further studied. Fig. 22 The plane structure, the structure without dielectric layer and the dielectric layer with positive interface charge (interface charge density is 10 12 cm -2 ) The relationship between the efficiency of solar cell devices and ion concentration under three conditions. The case without ions is given as a reference.

[0087] It can be seen that the device efficiency of the three solar cells decreases with the increase of ion concentration, and the attenuation degree of the planar structure with positive interface charge and the dielectric layer structure is more obvious than that of the dielectric layer structure without surface charge. 16cm -3 The JV characteristic curves of the three solar cell devices are as follows: Fig.23 The results show that the presence of ions leads to a decrease in the open circuit voltage regardless of the conditions. It is worth noting that when ions are present, the structure with local contact dielectric layer 1 shows a higher open circuit voltage than the planar structure, and the dielectric layer structure with positive interface charge shows a further enhancement.

[0088] Finally, based on the above comprehensive analysis and discussion, the present invention thoroughly optimizes the device from both optical and electrical performance aspects. Fig.24 The current-voltage curves of the optimized device and the original cell with a planar structure. It is worth noting that the basic parameters such as the interface defect density of the interface between the perovskite absorption layer 3 and the electron transport layer 2 and the local contact dielectric layer 1 remain consistent between the two devices. The only difference is the introduction of the local contact dielectric layer and its related parameters. The results show that the short-circuit current, open-circuit voltage and fill factor product, and device power conversion efficiency of the device have been significantly improved, among which the enhancement of the short-circuit current is attributed to optical optimization, and the enhancement of the open-circuit voltage and fill factor product is attributed to electrical optimization. Finally, a power conversion efficiency of 27.11% was achieved, which is a significant increase of 2.43% compared with the planar structure.

[0089] As an optional embodiment, the present invention also provides a method for preparing a perovskite solar cell, the preparation method adopts Figure 1 The structure shown in the figure is used to prepare a nip-type perovskite solar cell. The specific preparation process is as follows: S1: preparing tin oxide of about 180 nm as an electron transport layer on cleaned glass and ITO substrates to form electron transport layer 2; S2: spin coating a local contact dielectric layer solution on the prepared electron transport layer 2 to form a local contact dielectric layer 1; S3: spin-coating a layer of perovskite with a band gap of 1.53 eV on the prepared local contact dielectric layer 1, with a thickness of 600 nm, so that the perovskite fills the gaps between the local passivation layers and completely covers the local passivation layers, thereby forming a perovskite absorption layer 3; S4: preparing a layer of 2,2',7,7'-tetrakis[N,N-di(methoxyphenyl)amino]-9,9'-spirobifluorene as a hole transport layer 6 on the prepared perovskite absorption layer 3, with a thickness of 150 nm; S5: A layer of gold with a thickness of 100 nm is deposited on the prepared hole transport layer 6 by thermal evaporation to serve as the second electrode layer 7.

[0090] In summary, the beneficial effects of the present invention are: 1) By using a local contact dielectric layer 1 between the perovskite absorption layer 3 and the electron transport layer 2, the reflection in the short-wave band is effectively reduced, the light absorption of the perovskite absorption layer 3 is enhanced, and the photocurrent of the perovskite solar cell is significantly improved.

[0091] 2) Establishing a new carrier transport mode in perovskite solar cells, including direct carrier transport from the perovskite absorption layer 3 to the electron transport layer 2 and carriers above the local contact dielectric layer 1 are first transported laterally to the openings in the perovskite absorption layer 3 and then to the electron transport layer 2.

[0092] 3) The defects between the perovskite absorption layer 3 and the electron transport layer 2 are passivated by using the local contact dielectric layer 1, thereby reducing the non-radiative recombination at the interface, improving the open circuit voltage of the perovskite solar cell and ensuring the efficient transport of carriers to the transport layer at the same time, achieving a solution to balance the open circuit voltage and fill factor, and improving the photoelectric conversion efficiency of the perovskite solar cell; In addition, based on this scheme, the short-circuit current of 1.53eV perovskite solar cells can be reduced from 25.35mA / cm 2 Increased to 26.67mA / cm 2 The product of open circuit voltage and fill factor increased from 0.97 to 1.02, achieving a power conversion efficiency of 27.11% in NIP perovskite solar cells, avoiding the defects of high resistance and low fill factor when using a passivation layer.

[0093] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A local contact dielectric layer (1), characterized in that: The cross-sectional shape of the local contact dielectric layer (1) is a trapezoid, and the height of the trapezoid is 10-200 nm; The lower base of the trapezoid is connected to the electron transport layer (2), and the remaining portion is embedded in the perovskite absorption layer (3).

2. The local contact dielectric layer (1) according to claim 1, characterized in that: The local contact medium layer (1) is arranged in an array at the interface between the electron transport layer (2) and the perovskite absorption layer (3), with a period of 100 to 500 nm.

3. The local contact dielectric layer (1) according to claim 2, characterized in that: The local contact dielectric layer (1) has a lower bottom length of 0.1-450 nm and an upper bottom length of 1-450 nm.

4. The local contact dielectric layer (1) according to claim 3, characterized in that: The material of the local contact medium layer (1) is metal oxide.

5. The local contact dielectric layer (1) according to claim 4, characterized in that: The duty cycle of the local contact dielectric layer (1) is 1-90%.

6. The local contact dielectric layer (1) according to claim 5, characterized in that: The local contact dielectric layer (1) has a height of 120 nm, a period of 320 nm, a ratio of the upper base to the lower base of 0.2, and a duty cycle of 90%.

7. A perovskite solar cell, characterized in that: It comprises a first electrode layer (5), an electron transport layer (2), a local contact medium layer (1) as claimed in any one of claims 1 to 6, a perovskite absorption layer (3), a hole transport layer (6) and a second electrode layer (7) which are sequentially stacked on a substrate (4).

8. The perovskite solar cell according to claim 7, characterized in that: The band gap of the perovskite absorption layer (3) is 1.53 eV, and the material of the electron transport layer (2) is SnO2.

9. A method for preparing a perovskite solar cell, characterized in that: include, forming a first electrode layer (5) on a substrate (4); forming an electron transport layer (2) on the first electrode layer (5); forming a local contact medium layer (1) on the electron transport layer (2); forming a perovskite absorption layer (3) on the local contact dielectric layer (1); forming a hole transport layer (6) on the perovskite absorption layer (3); A second electrode layer (7) is formed on the hole transport layer (6).

10. The method for preparing a perovskite solar cell according to claim 9, characterized in that: The local contact dielectric layer (1) has a height of 120 nm, a period of 320 nm, a ratio of the upper base to the lower base of 0.2, and a duty cycle of 90%.

Images