Preparation of low-temperature and low-bombardment transparent conductive film and application thereof in perovskite / crystalline silicon laminated solar cell

Abstract

The application discloses a preparation of a low-temperature and low-bombardment transparent conductive film and application of the transparent conductive film in a perovskite / crystalline silicon laminated solar cell. The composite film is prepared by magnetron sputtering of TCO ceramic targets with different doping ratios at room temperature. ‑5 The composite transparent conductive oxide film is obtained by adjusting the sputtering pressure and power of the TCO film with different doping ratios and adjusting different growth modes, and the composite transparent conductive oxide film has a low-temperature and low-bombardment property. The lower layer of the composite transparent conductive oxide film is in a columnar crystal growth mode, and the upper layer is in an equiaxed large-grain growth mode. The composite transparent conductive oxide film can be applied in a perovskite / silicon laminated solar cell, can promote the vertical and horizontal transmission capacity of carriers in a TCO transparent electrode, promotes the effective collection and transmission of carrier charges, and thus a high-efficiency perovskite / silicon laminated solar cell is obtained.

Description

Technical Field

[0001] This invention relates to the field of transparent conductive oxide thin film preparation technology, specifically to a transparent conductive oxide thin film, its preparation method, and its application. Background Technology

[0002] Currently, the development of perovskite / silicon tandem solar cells faces challenges in light management, including enhancing the transmission of each thin film in the top cell (excluding the absorber layer) across a wide spectrum and reducing reflection. Therefore, for perovskite / silicon tandem solar cells, the selection of transparent electrodes is one of the key factors affecting cell efficiency. Transparent conductive oxide (TCO) films have advantages such as good conductivity and high optical transparency, and are widely used in the solar cell field. Currently, the most common TCO film systems include three types: doped SnO2, doped In2O3, and doped ZnO. Among them, the most representative is the doped In2O3 film, including indium tin oxide (ITO) film, indium zinc oxide (IZO) film, and indium zirconium oxide (IZrO) film. Among these TCOs, Zr-doped In2O3 has a higher carrier mobility due to less electron scattering [IEEE J Photovolt.2018;8(5):1202-1207]. In addition, due to its higher dielectric constant, zirconium-doped In2O3 can shift the plasma frequency to a longer wavelength in the near-infrared region, thereby increasing the near-infrared wavelength transmittance. Erkan-Aydin et al. reported that indium zirconium oxide (IZrO) is a promising material for transparent electrodes in perovskite solar cells due to its high transparency and low resistivity [Adv Funct Mater. 2019; 29(25):1901741]. Thermal annealing can induce a phase transition in IZrO films, improving their crystallinity. However, due to the damage to the lower absorber layer of perovskite / silicon tandem solar cells caused by high temperatures, thermal annealing of TCO transparent electrodes cannot achieve better performance in tandem devices. Moreover, high power density can also damage the lower layers of tandem solar cells. In addition, an efficient carrier transport path between the buffer layer and the transparent electrode is noteworthy. Typical monolayer indium zirconium oxide (IZrO) transparent electrodes tend to transport carriers laterally in equiaxed grains, which will hinder the vertical transport of carriers from the buffer layer to the upper layer [Sol.RRL. 2024; 8(6):2301029]. Therefore, the concept of stacking composite transparent conductive oxide thin films with different growth modes was introduced to maximize the crystallinity of TCO thin films prepared at room temperature. In addition, the low sputtering power of the first layer of the composite thin film can reduce the bombardment of the lower layer of the device. Thus, the introduction of composite TCO transparent electrodes in perovskite / silicon tandem solar cells promotes the vertical and lateral transport of charge carriers in the solar cells, and promotes the effective collection and transport of charge carriers. Summary of the Invention

[0003] The purpose of this invention is to solve the above-mentioned problems in the prior art and to provide a low-temperature, low-bombardment composite transparent conductive film, its preparation method, and its application.

[0004] The technical solution adopted in this invention is:

[0005] First, this invention provides a method for preparing a low-temperature, low-bombardment composite transparent conductive film, comprising the following steps:

[0006] 1) Using an argon-oxygen mixture as the reactant gas, IZrO thin films with different doping concentrations were deposited on the substrate at room temperature by magnetron sputtering deposition. By controlling the growth mode, two TCO thin films with different crystallization modes were obtained, which is beneficial to the longitudinal and lateral transport of charge carriers in the thin film.

[0007] 2) Two TCO films with different crystallization modes are combined into a composite film and applied as a transparent electrode in perovskite / silicon tandem solar cells to improve the vertical and lateral transport capabilities of charge carriers in the solar cells.

[0008] In step 1), before sputtering, the substrate is cleaned in an ultrasonic bath of acetone and isopropanol. IZrO ceramic targets with In2O3:ZrO2 = 95wt%:5wt% and In2O3:ZrO2 = 98wt%:2wt% are selected for sputtering. For monolayer IZrO films, IZrO targets with 2wt% Zr doping are selected for sputtering. For composite IZrO films, IZrO targets with 5wt% and 2wt% Zr doping are selected for sputtering.

[0009] The different crystallization modes mentioned are columnar crystallization and equiaxed crystallization.

[0010] Furthermore, the temperature of the substrate in step 1) is room temperature.

[0011] Step 1) The reaction gas is a 3% argon-oxygen mixture; wherein the partial pressure of O X = O2 / (Ar+O2)%, when X = 0.06%, the sputtering power is adjusted to start depositing the IZrO thin film, and the deposition rate is ~0.4nm / min; the sputtering power is 25W-50W; preferably, it is 25W, 30W, 35W, 40W, 45W, 50W.

[0012] The deposited TCO films in step 1) have different crystallization modes with different doping ratios. Specifically, the 5wt% Zr-doped IZrO film deposited at 1.2 mtorr and a sputtering power of 35 W tends to have columnar crystallization, while the 2wt% Zr-doped IZrO film sputtered at 0.9 mtorr and a sputtering power of 45 W tends to have equiaxed crystallization.

[0013] The sputtering pressure of the deposited TCO thin film in step 1) has different crystallization modes; wherein the sputtering pressure is 0.6 mtorr-1.5 mtorr; preferably, it is 0.6 mtorr, 0.9 mtorr, 1.2 mtorr, or 1.5 mtorr.

[0014] Furthermore, the composite transparent conductive oxide film described in step 2) requires low-bombardment preparation, and the lower layer of the composite film requires low-power preparation.

[0015] Step 2) The composite transparent conductive oxide film is prepared by adjusting the thickness ratio of different crystalline layers to achieve a mobility of 20 cm⁻¹. 2 ·V -1 ·s -1 ~50cm 2 ·V -1 ·s -1 The carrier concentration is 3×10 20 cm -3 ~1×10 21 cm -3 .

[0016] Step 2) The composite transparent conductive oxide film is prepared by adjusting the thickness ratio of different crystalline layers to obtain a sheet resistance ≤30Ωsq. -1 .

[0017] Step 2) The composite transparent conductive oxide film has good transmittance in the visible light and near-infrared bands of 400-1200nm, with an average transmittance of ≥80%.

[0018] The present invention also provides the application of the low-temperature, low-bombardment transparent conductive film obtained by the above preparation method in perovskite / crystalline silicon tandem solar cells. The TCO composite transparent conductive film is applied to the perovskite / silicon tandem solar cells as a transparent electrode, which promotes the vertical and lateral transport capability of charge carriers in the solar cells and has good optical transmittance, thus obtaining a high-efficiency perovskite / silicon tandem solar cell.

[0019] Advantages and positive effects of the present invention: The present invention proposes the concept of composite transparent conductive film to maximize the crystallinity of TCO film prepared at room temperature, and the low sputtering power of the first layer of composite film can also reduce the bombardment of the lower layer of the device. Therefore, composite TCO transparent electrode is introduced into tandem solar cells. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the perovskite / silicon tandem solar cell used in this invention.

[0021] Figure 2 This is a schematic diagram of the carrier transport path for an equiaxial TCO thin film used as the transparent front electrode in a multilayer device.

[0022] Figure 3 This is a schematic diagram of the carrier transport path when a columnar TCO thin film is used as the transparent front electrode of a multilayer device.

[0023] Figure 4 FoM (FoM = T) for preparing IZrO thin films by sputtering at different power 10 / R sq )parameter.

[0024] Figure 5 Carrier mobility (μ), carrier concentration (N), and sheet resistance (R) of IZrO thin films prepared by sputtering at different gas pressures were measured. sq ).

[0025] Figure 6 To determine the sheet resistance (R) of composite transparent conductive IZrO thin films under different thickness ratios sq ).

[0026] Figure 7 JV curves for a single-layer transparent conductive IZrO thin film as the transparent front electrode of a stacked device.

[0027] Figure 8 JV curves for composite transparent conductive IZrO thin films as the transparent front electrode of stacked devices. Detailed Implementation

[0028] The present invention will be further explained and described below with reference to specific embodiments.

[0029] Example 1:

[0030] In this embodiment, a zirconium-doped indium oxide (IZrO) thin film is deposited on a glass substrate by magnetron sputtering.

[0031] 1) Before sputtering, the substrate was cleaned in an ultrasonic bath of acetone and isopropanol for 10 minutes. IZrO ceramic targets with In₂O₃:ZrO₂ ratios of 95wt%:5wt% and 98wt%:2wt% were used for sputtering, respectively. For monolayer IZrO films, a 2wt% Zr-doped IZrO target was used for sputtering, and its parameters were adjusted. For composite IZrO films, 5wt% and 2wt% Zr-doped IZrO targets were used for sputtering, and their process parameters were adjusted. The basic vacuum pressure in the chamber before deposition was less than 1×10⁻⁶. -5 Pa, the distance between the substrate and the target is maintained at 190 mm.

[0032] 2) Place the cleaned glass substrate into the magnetron sputtering system, ensuring the basic vacuum pressure in the chamber is less than 1×10⁻⁶. - 5After Pa, an IZrO ceramic target with an In2O3:ZrO2 ratio of 98wt%:2wt% was selected for sputtering. During sputtering, 100 sccm of argon gas was first introduced to initiate the process, and the sputtering power was set to 40W. After successful ignition, argon and oxygen were introduced as reactants, with oxygen accounting for 3% of the total volume. The substrate (glass) temperature was set to room temperature, and the partial pressure of O (X = O2 / (Ar+O2)%) was adjusted during sputtering. When X = 0.06%, the sputtering power was adjusted to 25W, 30W, 35W, 40W, 45W, and 50W respectively to begin depositing the IZrO thin film. The deposition rate was controlled at ~0.4 nm / min, and the deposition thickness was 100 nm, resulting in the deposited thin film.

[0033] 3) Compare the photoelectric performance by comparing the FoM parameters of IZrO thin films under different sputtering powers, where FoM = T 10 / R sq ), where T is the average transmittance of this band, and R sq For thin-film sheet resistors, the best photoelectric performance was obtained at 35W and 45W. Figure 4 However, high power density can damage the underlying layers of tandem solar cells due to bombardment, and the surface becomes rougher.

[0034] Example 2:

[0035] 1) Place the cleaned glass substrate into the magnetron sputtering system, with the basic vacuum pressure in the chamber less than 1×10⁻⁶. - 5 After Pa, an In2O3:ZrO2 ceramic target with a composition of 98wt%:2wt% was selected for sputtering. During sputtering, 100 sccm of argon gas was first introduced to initiate the process, and the sputtering power was set to 40W. After successful ignition was observed, argon and oxygen were then introduced as the reaction gases, with oxygen comprising 3% by volume. The substrate (glass) temperature was set to room temperature, and the deposition gas pressures were controlled at 0.6 mtorr, 0.9 mtorr, 1.2 mtorr, and 1.5 mtorr. Figure 5 As shown, when the sputtering pressure is 0.9 mtorr, due to less scattering, the IZrO thin film sputtered at 0.9 mtorr has a thickness of 27.7 cm⁻¹. 2 ·V -1 ·s -1 It exhibits high mobility with a carrier concentration of 4.3 × 10⁻⁶. 20 cm -3 It tends to crystallize equiaxed. The mobility of the IZrO film deposited at 1.2 mtorr was 15.7 cm⁻¹. 2 ·V -1 ·s -1 The carrier concentration reached 7×1020 cm -3 It tends to crystallize in a columnar manner. The R... sq As low as 40.3Ωsq -1 The Rsq of the IZrO film deposited at 1.2 mtorr is 43.6 Ωsq. -1 .

[0036] Example 3:

[0037] At 1.2 motorr, a 5 wt% Zr-doped IZrO film deposited at a sputtering power of 35 W tends to exhibit columnar crystallization. At 0.9 motorr, a 2 wt% Zr-doped IZrO film sputtered at a sputtering power of 45 W tends to exhibit equiaxed crystallization. Figure 6 As shown, when the total thickness is controlled at 130 nm and the thickness ratio of the lower columnar crystalline layer to the upper equiaxed crystalline layer is 55:75 nm, the IZrO thin film achieves the best electrical and optical properties, with a sheet resistance as low as 25.55 Ω·sq. -1 .

[0038] Example 4:

[0039] 1) In this embodiment, the perovskite / silicon tandem solar cell structure is as follows: Figure 1 As shown, from bottom to top, they include:

[0040] The metal gate electrode is silver (Ag), the transparent conductive oxide thin film is indium tin oxide (ITO), the p-type doped amorphous silicon (pa-Si:H), the intrinsic passivation layer (ia-Si:H), the n-type textured substrate (n-type wafer), the intrinsic passivation layer (ia-Si:H), the n-type doped amorphous silicon (na-Si:H), the n-type doped nanocrystalline silicon (n-nc-Si:H), the p-type doped nanocrystalline silicon (p-nc-Si:H), and the Spiro-TTB is <6.5×10⁻⁶. -6 Under working pressure of mbar Thermal evaporation rate. A one-step spin-coating deposition of a perovskite absorber layer, at a rate <2×10⁻⁶. -6 Under the working pressure of mbar, Evaporation rate at 15nm C 60 A 20 nm SnO2 prepared by atomic layer deposition (ALD) was used as a buffer layer, and a 130 nm 2 wt% Zr-doped IZrO transparent electrode was prepared by magnetron sputtering with a sputtering power of 45 W, X = 0.06% (X = O2 / (Ar+O2)%), and a sputtering pressure of 0.9 mtorr.

[0041] 2) The open-circuit voltage of the solar cell prepared in this embodiment is 1876mV, and the short-circuit current density is 19.72mA / cm².2 The fill factor is 75.57%, and the photoelectric conversion efficiency is 27.95%; the open-circuit voltage of the reverse scan is 1851mV, and the short-circuit current density is 19.70mA / cm². 2 The fill factor is 73.34%, and the photoelectric conversion efficiency is 26.75%. Figure 7 ).

[0042] Example 5:

[0043] 1) In this embodiment, the perovskite / silicon tandem solar cell structure is as follows: Figure 1 As shown, from bottom to top, they include:

[0044] The metal gate electrode is silver (Ag), the transparent conductive oxide thin film is indium tin oxide (ITO), the p-type doped amorphous silicon (pa-Si:H), the intrinsic passivation layer (ia-Si:H), the n-type textured substrate (n-type wafer), the intrinsic passivation layer (ia-Si:H), the n-type doped amorphous silicon (na-Si:H), the n-type doped nanocrystalline silicon (n-nc-Si:H), the p-type doped nanocrystalline silicon (p-nc-Si:H), and the Spiro-TTB is <6.5×10⁻⁶. -6 Under working pressure of mbar Thermal evaporation rate. A one-step spin-coating deposition of a perovskite absorber layer, at a rate <2×10⁻⁶. -6 Under the working pressure of mbar, Evaporation rate at 15nm C 60 A composite IZrO transparent electrode was prepared using a 20 nm SnO2 layer prepared by atomic layer deposition (ALD) as a buffer layer, a first layer of 55 nm with a sputtering power of 35 W and a sputtering capacity of 1.2 mtorr, and a second layer of 75 nm with a sputtering power of 45 W and a sputtering capacity of 0.9 mtorr.

[0045] 2) The open-circuit voltage of the solar cell prepared in this embodiment is 1902mV, and the short-circuit current density is 19.64mA / cm². 2 The fill factor is 78.61%, and the photoelectric conversion efficiency is 29.37%; the open-circuit voltage of the reverse scan is 1885mV, and the short-circuit current density is 19.64mA / cm². 2 The fill factor is 76.77%, and the photoelectric conversion efficiency is 28.43%. Figure 8 ).

[0046] Based on the above embodiments, this invention provides a method for preparing a low-temperature, low-bombardment transparent conductive film, and provides the application of the obtained transparent conductive film in perovskite / crystalline silicon tandem solar cells. Simultaneously, the influence factors of the transparent conductive oxide film growth crystallization mode on carrier transport and collection in perovskite / silicon solar cells, the influence factors of the transparent conductive oxide film crystallization mode, and the influence factors of the TCO crystallization growth mode were investigated.

[0047] First, the influence of the growth and crystallization mode of transparent conductive oxide thin films on carrier transport and collection in perovskite / silicon solar cells was determined.

[0048] Figure 1 This is a schematic diagram of the perovskite / silicon tandem solar cell we are using. Figure 2 This diagram illustrates the structure and carrier transport path of an equiaxed TCO thin film as the transparent front electrode in a multilayer device. Figure 2 As shown, charge carriers do not have good vertical transport capability in equiaxed crystalline TCO films. Therefore, when charge carriers transfer from the buffer layer to the equiaxed TCO transparent electrode, some charge carriers will be trapped in the grain boundaries. Figure 3 This diagram illustrates the carrier transport path of a columnar TCO thin film used as the transparent front electrode in a tandem device. While columnar crystalline IZrO films exhibit good vertical transport capabilities, their low carrier mobility prevents effective collection by the metal electrodes. Therefore, a transparent front electrode with both good vertical and lateral transport capabilities is crucial in perovskite / silicon tandem solar cells.

[0049] Secondly, the factors affecting the crystallization mode of transparent conductive oxide thin films were determined, including: the proportion of dopants in In2O3, sputtering pressure, sputtering oxygen partial pressure, sputtering power, etc.

[0050] Based on previous research results, TCO with a higher doping ratio tends to have columnar crystals, while TCO with a moderately low doping ratio tends to have equiaxed crystals [J Electroceram. 2009; 23: 169-174].

[0051] Secondly, it is necessary to determine the effect of working pressure on the crystallization mode of transparent conductive oxide thin films during the coating process. Working pressure affects the number of gas ions bombarding the target in the chamber. The higher the pressure, the more ions are sputtered, thus affecting the sputtering rate, and the particles have less growth space, tending to form columnar crystals. Similarly, the lower the pressure, the sputtered ions have more growth space, tending to form equiaxed crystals.

[0052] The oxygen-argon flow ratio determines whether the thin film is in an oxygen-deficient or oxygen-rich environment during the preparation process, which in turn determines the oxygen vacancy concentration in the thin film and thus affects the electrical properties of the thin film, such as carrier concentration and mobility.

[0053] The sputtering power is related to the sputtering rate and the bombardment of the underlying layer during thin film preparation. The sputtering rate increases with the increase of power and the sheet resistance decreases, but it is easy to cause oxygen deficiency reaction, resulting in reduced permeability. It needs to be coordinated and controlled with oxygen and argon flow rates.

[0054] Third, we identified the influencing factors affecting the TCO crystal growth mode. We combined columnar TCO films and equiaxed TCO films to form a composite transparent conductive oxide film, which was then applied to perovskite / silicon solar cells.

[0055] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a low-temperature, low-bombardment transparent conductive thin film, characterized in that, Includes the following steps: 1) Using an argon-oxygen mixture as the reactant gas, IZrO thin films with different doping concentrations were deposited on the substrate at room temperature by magnetron sputtering deposition. By controlling the growth mode, two TCO thin films with different crystallization modes were obtained, which is beneficial to the longitudinal and lateral transport of charge carriers in the thin film. 2) Two TCO films with different crystallization modes are combined into a composite film and applied as a transparent electrode in perovskite / silicon tandem solar cells to improve the vertical and lateral transport capabilities of charge carriers in the solar cells. The different crystallization modes mentioned are columnar crystallization and equiaxed crystallization; In step 1), before sputtering, the substrate is cleaned in an ultrasonic bath of acetone and isopropanol. IZrO ceramic targets with In2O3:ZrO2 = 95 wt%: 5 wt% and In2O3:ZrO2 = 98 wt%: 2 wt% are selected for sputtering. For composite IZrO thin films, IZrO targets with 5 wt% and 2 wt% Zr doping are selected for sputtering. The reaction gas in step 1) is a 3% argon-oxygen mixture; wherein the partial pressure of O X = O2 / (Ar+O2)%. When X = 0.06%, the sputtering power is adjusted to start depositing the IZrO thin film at a deposition rate of 0.4 nm / min. The deposited TCO films in step 1) exhibit different crystallization modes with different doping ratios. Specifically, the 5 wt% Zr-doped IZrO film deposited at a deposition gas pressure of 1.2 mtorr and a sputtering power of 35 W tends to exhibit columnar crystallization, while the 2 wt% Zr-doped IZrO film sputtered at a deposition gas pressure of 0.9 mtorr and a sputtering power of 45 W tends to exhibit equiaxed crystallization. The total thickness of the composite film is 130 nm, and the thickness ratio of the lower columnar crystal layer to the upper equiaxed crystal layer is 55:75 nm.

2. The preparation method according to claim 1, characterized in that: The temperature of the substrate in step 1) is room temperature.

3. The application of the low-temperature, low-bombardment transparent conductive film obtained by the preparation method of claim 1 or 2 in perovskite / crystalline silicon tandem solar cells, characterized in that: Transparent conductive films are used as transparent electrodes in perovskite / silicon tandem solar cells.

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