Perovskite solar cell and preparation method thereof

Abstract

This invention discloses a perovskite solar cell, comprising a transparent conductive layer, a hole transport layer, a perovskite absorber layer, an electron transport layer, and a back electrode layer stacked sequentially. The back electrode layer is a composite structure of an ITO layer and a metal layer. The perovskite solar cell also includes a dipole layer located between the electron transport layer and the ITO layer, with the dipole moment of the dipole layer pointing from the electron transport layer to the ITO layer. By incorporating a dipole layer in the perovskite solar cell, the work function of the electron transport layer and the back electrode layer is modulated to reduce the extraction barrier, resulting in a significant linear increase in the device's built-in potential, and substantial improvements in fill factor, photovoltage, and power conversion efficiency. Furthermore, the excellent ion-blocking ability of the dielectric material alumina enhances the drift scattering blocking effect of the P-N junction, effectively preventing ion migration within the device.

Description

Technical Field

[0001] This invention relates to the field of perovskite solar cells, and particularly to a perovskite solar cell with adjustable work function and its fabrication method. Background Technology

[0002] Perovskite solar cells, due to their high efficiency and potential low levelized cost of energy (LCOE), are currently the most promising next-generation photovoltaic technology, attracting the attention of numerous researchers and companies. Although the power conversion efficiency of perovskite solar cells has been significantly improved, their operational stability is still insufficient for commercial application. Ion migration remains one of the main causes of device performance degradation during long-term operation, as it not only accelerates material degradation but also triggers interfacial chemical reactions, reducing charge transport and corroding the electrode layer (more severe under reverse bias), which seriously reduces the long-term stability of perovskite devices. To address the stability issues caused by ion migration, one of the main strategies for suppressing ion interface migration is to use dielectric material blocking layers to prevent ion migration. These dielectric materials can effectively prevent the free movement of ions within the device through physical barriers. However, in the perovskite field, dielectric materials mainly focus on optimizing the upper and lower interfaces of the perovskite active layer. To achieve further breakthroughs in device performance, expanding research beyond the interface to other key aspects (such as the bulk phase of the charge carrier transport layer and the electrode interface) is crucial and holds great potential. Of particular note is the achievement of high-efficiency perovskite solar cells with excellent reverse bias stability through a composite electrode strategy combining transparent conductive oxide (TCO) with inexpensive metals (Cu, Ag), representing a significant breakthrough in improving the stability of perovskite solar cells. However, the introduction of ITO / Cu composite electrodes in inverted perovskite devices can lead to more severe energy mismatch at the electron transport layer and electrode charge extraction contact.

[0003] To further reduce nonradiative recombination at the interface and manufacture efficient and stable optoelectronic devices, this patent proposes an application that uses atomic force deposition (ALD) to control the pulse ratio of the precursor to prepare an alumina dipole interlayer. This simultaneously increases the work function of indium tungsten oxide (IWSO) and decreases the work function of indium tin oxide (ITO), solving the work function mismatch problem between the transparent conductive oxide and the charge transport layer and improving carrier extraction efficiency. At the same time, the dielectric material itself exhibits excellent ion blocking ability due to its lattice scattering effect, further enhancing interface stability. Summary of the Invention

[0004] The main technical problem solved by this invention is that the electron transport layer in an inverted perovskite structure is generally made of tin dioxide ( Materials such as indium tungsten tin oxide (IWSO) are used, while the back electrode layer typically uses indium tin oxide (ITO). Due to significant work function deviations between these materials, a severe energy mismatch occurs at the charge extraction contact between the electron transport layer and the back electrode (the work function indicates the semiconductor's ability to bind electrons). The work function of is smaller, while the work function of ITO is larger, therefore It will have a weaker ability to bind electrons inside, when When in contact with ITO, electrons will move from... The flow towards ITO creates a potential barrier.

[0005] To solve the above-mentioned technical problems, one technical solution adopted by the present invention is: a perovskite solar cell, comprising a transparent conductive layer, a hole transport layer, a perovskite absorber layer, an electron transport layer and a back electrode layer stacked sequentially; the back electrode layer is a composite structure of an ITO layer and a metal layer; The perovskite solar cell further includes a dipole layer located between the electron transport layer and the ITO layer, wherein the dipole moment of the dipole layer is directed from the electron transport layer to the ITO layer.

[0006] Furthermore, the dipole moment is between 3.0 and 4.0D.

[0007] Furthermore, the dipole layer is a non-stoichiometric alumina layer, a non-stoichiometric silicon oxide layer, or a non-stoichiometric hafnium oxide layer.

[0008] Furthermore, the formation process of the non-stoichiometric alumina layer, non-stoichiometric silicon oxide layer, or non-stoichiometric hafnium oxide layer is an atomic layer deposition process.

[0009] Furthermore, the thickness of the dipole layer is 0.1 nm-1 nm.

[0010] Furthermore, the perovskite solar cell also includes a passivation layer, which is disposed between the hole transport layer and the perovskite absorber layer and / or between the perovskite absorber layer and the electron transport layer.

[0011] A method for fabricating a perovskite solar cell includes the following steps: Furthermore, a transparent conductive layer is provided, on which a hole transport layer, a perovskite absorption layer, and an electron transport layer are sequentially formed; A dipole layer is formed on the electron transport layer by atomic layer deposition; An ITO layer and a metal layer are sequentially formed on the dipole layer to serve as the back electrode layer. The dipole moment direction of the dipole layer is from the electron transport layer to the ITO layer.

[0012] Furthermore, the dipole layer is a non-stoichiometric alumina layer; Furthermore, in the atomic layer deposition process, water is first introduced for a first pulse deposition, and then an aluminum source precursor is introduced for a second pulse deposition. The first pulse deposition and the second pulse deposition are performed alternately multiple times to form the dipole layer.

[0013] Furthermore, the duration of the first pulse is 1 second, and the duration of the second pulse is 1.5 seconds.

[0014] Furthermore, the thickness of the dipole layer is 0.1 nm to 1 nm. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the energy levels of different electron transport materials and perovskites; Figure 2 This is a schematic diagram illustrating the inhibitory effect of the dipole layer on the band structure of the electron transport layer and the back electrode layer, and on the migration of iodine ions. Figure 3 A schematic diagram of an inverted perovskite structure; Figure 4 Experimental data on the coexistence of dipole layers and passivation layers at different interfaces; Figure 5 Experimental data on the coexistence of dipole layers and passivation layers at different interfaces; Detailed Implementation

[0016] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0017] Currently, tin dioxide is generally used as the electron transport layer in inverted perovskite structures. Materials such as indium tungsten tin oxide (IWSO) are used, while the composite electrode layer (i.e., the back electrode layer) is generally made of indium tin oxide (ITO). Due to the significant work function deviation between these materials, a severe energy mismatch occurs at the charge extraction contact between the electron transport layer and the composite electrode (the work function indicates the semiconductor's ability to bind electrons). The work function of is smaller, while the work function of ITO is larger, therefore It will have a weaker ability to bind electrons inside, when When in contact with ITO, electrons will move from... The flow towards ITO creates a potential barrier.

[0018] This application provides a perovskite solar cell, comprising a transparent conductive layer, a hole transport layer, a perovskite absorber layer, an electron transport layer, and a back electrode layer. A dipole layer is introduced into the electron transport layer and the back electrode layer, with the dipole direction pointing from the electron transport layer to the back electrode layer. This results in a downward stretching of the work function of the electron transport layer and an upward stretching of the work function of the back electrode layer, thereby achieving work function regulation and reducing the extraction barrier.

[0019] This invention provides a method for fabricating this perovskite solar cell, comprising the following steps: Step 1: The FTO conductive glass is ultrasonically cleaned sequentially with glass cleaner and deionized water, repeated 2-3 times, and then thoroughly dried in an oven at 100℃ to obtain a clean FTO transparent conductive layer; Step 2: A hole transport layer is prepared on the transparent conductive layer; a nickel oxide hole transport layer with a thickness of 25 nm is obtained by magnetron sputtering on the FTO glass using an RF power supply. Step 3: Deposit a perovskite solution on the hole transport layer using a slot coating process to form a wet film. After drying, the wet film is then annealed and crystallized to obtain the perovskite absorption layer. Step 4: A 7 nm thick layer is deposited on the perovskite absorber surface using vacuum evaporation and atomic layer deposition methods under a vacuum level less than 10⁻⁴ Pa via thermal evaporation. , The deposition rate was 0.5 Å / s; atomic layer deposition was performed at a vacuum level of less than 10⁻¹ Pa and a temperature of 110 °C. A 18nm thick tin oxide layer is deposited on the surface to obtain the electron transport layer; Step 5: Using ALD atomic layer deposition, by controlling the deposition process, water is first deposited to construct hydroxyl groups (-OH), and then aluminum source is deposited to form -O and -AL bonds with the hydroxyl groups. The direction is from the electron transport layer to the back electrode layer, and the dipole moment is between 3.0 and 4.0D. It should be noted that water pulse is performed first, with a pulse time of 1 second, and then aluminum source precursor pulse is performed, with a pulse time of 1.5 seconds. After one cycle, a dipole layer with a thickness of 0.1 nm is obtained. The aluminum source precursor in step 5 can be a TMA or DMEAA aluminum source precursor. In this embodiment, the TMA aluminum source is used. By differentiating the timing of the first pulse and the second pulse, the total number of aluminum atoms and oxygen atoms is controlled so that the number of aluminum atoms is greater than the number of oxygen atoms.

[0020] Step 6: Using radio frequency magnetron sputtering on the surface of the dipole layer, under a vacuum degree of less than 1*10-3 Pa, 20 nm ITO and 100 nm IZO, and 80 nm Cu, respectively, are deposited to prepare the composite electrode, thus obtaining the perovskite solar cell.

[0021] Example 2 The difference from Example 1 is that in step 5, ALD atomic force deposition is cycled 3 times to obtain a dipole layer with a thickness of 0.3 nm; Example 3 The difference from Example 1 is that in step 5, ALD atomic force deposition is cycled 5 times to obtain a dipole layer with a thickness of 0.5 nm; Example 4 The difference from Example 1 is that in step 5, ALD atomic force deposition is cycled 8 times to obtain a dipole layer with a thickness of 0.8 nm; Example 5 The difference from Example 1 is that in step 5, ALD atomic force deposition is cycled 10 times to obtain a dipole layer with a thickness of 0.8 nm; Comparative Example 1 The following steps are taken to fabricate a perovskite solar cell without a dipole layer: Step 1: The FTO conductive glass is ultrasonically cleaned with glass cleaner and deionized water in sequence, repeated 2-3 times, and then thoroughly dried in an oven at 100℃ to obtain a clean FTO transparent conductive layer. Step 2: Prepare a hole transport layer on the transparent conductive layer; use an RF power supply to perform magnetron sputtering on FTO glass to obtain a nickel oxide hole transport layer with a thickness of 25 nm; Step 3: Deposit a perovskite solution on the hole transport layer using a slot coating process to form a wet film. After drying, the wet film is then annealed and crystallized to obtain the perovskite absorption layer. Step 4: A 7 nm thick layer is deposited on the perovskite absorber surface using vacuum evaporation and atomic layer deposition methods under a vacuum level less than 10⁻⁴ Pa via thermal evaporation. , The deposition rate was 0.5 Å / s; atomic layer deposition was performed at a vacuum level of less than 10⁻¹ Pa and a temperature of 110 °C. A 18nm thick tin oxide layer is deposited on the surface to obtain the electron transport layer; Step 5: Using radio frequency magnetron sputtering on the surface of the electron transport layer, under a vacuum degree of less than 1*10-3 Pa, 20 nm transparent conductive oxide ITO and 100 nm IZO and 80 nm active metal Cu are deposited to prepare composite electrodes, thus obtaining the perovskite solar cell.

[0022] As shown in the table above, the comparative analysis of the examples and comparative examples reveals that the influence of dielectric material dipoles on the electron transport layer and composite electrode layer follows certain patterns. First, the introduction of the ALOx dipole layer significantly promotes the open-circuit voltage and fill factor of the device. Second, its effect is further enhanced with the increase of the dipole layer thickness. When the dipole layer thickness is 0.8 nm, the open-circuit voltage and fill factor are improved to the greatest extent.

[0023] In this embodiment, the dielectric material used in the dipole layer is non-stoichiometric alumina. Other dielectric materials can also be used, such as non-stoichiometric hafnium oxide (HfO2) and non-stoichiometric silicon oxide (…). )wait.

[0024] In the current inverted perovskite structure, the severe energy mismatch at the charge extraction contact caused by the deviation of the work function and the ion migration caused by non-radiative recombination not only exist in the electron transport layer and the recombination electrode layer, but also occur in the hole transport layer, the perovskite absorption layer and inside the electron transport layer. Therefore, this application also includes several other embodiments.

[0025] Furthermore, passivation layers can be introduced into the hole transport layer and the perovskite absorber layer, as well as the perovskite absorber layer and the electron transport layer, such as... Figure 4 and Figure 5 As shown, passivation layers can be introduced into the hole transport layer and the perovskite absorber layer, as well as the perovskite absorber layer and the electron transport layer. These passivation layers, working in conjunction with the dipole layer between the electron transport layer and the back electrode, suppress ion interface migration at different layers in the perovskite solar cell, improve carrier extraction efficiency, and further enhance interface stability. It is important to note that the pulse sequence is different when introducing passivation layers into the hole transport layer and the perovskite absorber layer, as well as the perovskite absorber layer and the electron transport layer, using atomic force deposition (AFM). When introducing the dipole layer, aluminum source pulse deposition is performed first, followed by water source pulse deposition to construct hydroxyl groups (-OH), forming -O and -AL bonds. In this comparative example, TMA is used for aluminum source pulse deposition, with a TMA pulse duration of 1 second. A 1-second pulse was used to construct a passivation layer film of non-stoichiometric alumina.

[0026] In summary, introducing a dipole layer into a perovskite solar cell, with its dipole direction pointing from the electron transport layer to the ITO layer, thereby improving the performance of the solar cell... The work function of the dielectric material exhibits a downward stretch, while the work function of ITO exhibits an upward stretch. This allows for the manipulation of the work function to reduce the extraction barrier, resulting in a significant linear increase in the device's built-in potential, and substantial improvements in fill factor, photovoltage, and power conversion efficiency. Furthermore, the excellent ion-blocking capability of the dielectric material itself and the enhanced interfacial dipole layer enhance the PN junction drift scattering blocking effect, effectively preventing ion migration within the device.

[0027] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A perovskite solar cell, characterized in that, It includes a transparent conductive layer, a hole transport layer, a perovskite absorption layer, an electron transport layer, and a back electrode layer stacked sequentially; the back electrode layer is a composite structure of an ITO layer and a metal layer; The perovskite solar cell further includes a dipole layer located between the electron transport layer and the ITO layer, wherein the dipole moment of the dipole layer is directed from the electron transport layer to the ITO layer.

2. The perovskite solar cell according to claim 1, characterized in that, The dipole moment is between 3.0 and 4.0D.

3. A perovskite solar cell according to claim 1, characterized in that, The dipole layer is a non-stoichiometric alumina layer, a non-stoichiometric silicon oxide layer, or a non-stoichiometric hafnium oxide layer.

4. A perovskite solar cell according to claim 3, characterized in that, The process for forming the non-stoichiometric alumina layer, non-stoichiometric silicon oxide layer, or non-stoichiometric hafnium oxide layer is an atomic layer deposition process.

5. A perovskite solar cell according to claim 4, characterized in that, The thickness of the dipole layer is 0.1 nm to 1 nm.

6. A perovskite solar cell according to claim 1, characterized in that, The perovskite solar cell further includes a passivation layer disposed between the hole transport layer and the perovskite absorber layer and / or between the perovskite absorber layer and the electron transport layer.

7. A method for fabricating a perovskite solar cell, characterized in that, Includes the following steps: A transparent conductive layer is provided, on which a hole transport layer, a perovskite absorption layer, and an electron transport layer are sequentially formed. A dipole layer is formed on the electron transport layer by atomic layer deposition; An ITO layer and a metal layer are sequentially formed on the dipole layer to serve as the back electrode layer. The dipole moment direction of the dipole layer is from the electron transport layer to the ITO layer.

8. The preparation method according to claim 7, characterized in that, The dipole layer is a non-stoichiometric alumina layer; In the atomic layer deposition process, water is first introduced for the first pulse deposition, and then an aluminum source precursor is introduced for the second pulse deposition. The first pulse deposition and the second pulse deposition are performed alternately multiple times to form the dipole layer.

9. The preparation method according to claim 8, characterized in that, The duration of the first pulse is 1 second, and the duration of the second pulse is 1.5 seconds.

10. The preparation method according to claim 9, characterized in that, The thickness of the dipole layer is 0.1 nm to 1 nm.

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