A current-matched enhanced silicon- calcium- calcium triple-junction tandem photovoltaic device and a method of making the same

Abstract

The application discloses a current matching enhanced silicon calcium calcium triple-junction stacked photovoltaic device and a preparation method, and belongs to the technical field of stacked solar cells. The device comprises a silicon bottom cell, an intermediate cell and a wide-bandgap perovskite top cell which are stacked in sequence from bottom to top. The intermediate cell comprises a conventional bandgap perovskite main absorption layer, a passivation layer and an organism heterojunction compensation layer which are stacked in sequence. The organism heterojunction compensation layer is used for compensating for the photocurrent gap of the intermediate cell in the 780-900 nm waveband, so as to enhance the external quantum efficiency response of the intermediate cell in the waveband and make the equivalent EQE cutoff edge of the intermediate cell extend to the long-wave direction. The application has little influence on the long-wave response of the silicon bottom cell while improving the series limiting current of the device, realizes the long-wave gap compensation of the intermediate cell, the long-wave response reservation of the silicon bottom cell and the current matching improvement of the triple-junction device.

Description

Technical Field

[0001] This invention belongs to the field of tandem solar cell technology, specifically relating to a current-matched enhanced silicon-calcium-calcium triple junction tandem photovoltaic device and its fabrication method. Background Technology

[0002] Tandem photovoltaic (PV) devices utilize multiple photovoltaic sub-cells with different bandgap along the light incident direction, allowing different wavelengths of sunlight to be absorbed by their respective sub-cells, thereby improving the utilization of the solar spectrum. Silicon / perovskite / perovskite triple-junction PV devices typically consist of a wide-bandgap perovskite top cell, a middle perovskite sub-cell, and a silicon substrate cell. The wide-bandgap perovskite top cell primarily absorbs short-wavelength high-energy photons, the middle perovskite sub-cell primarily absorbs photons in the medium wavelength range, and the silicon substrate cell primarily absorbs long-wavelength photons transmitted through the top sub-cell. Since triple-junction PV devices are usually connected in series, the operating current is determined by the sub-cell with the lowest integrated photocurrent; therefore, current matching among the three sub-cells is a key factor affecting device performance.

[0003] In existing silicon / perovskite / perovskite triple-junction photovoltaic devices, the spectral response and current matching of each sub-cell are usually improved by adjusting the bandgap of the wide-bandgap perovskite top cell and the middle perovskite sub-cell, changing the thickness of the perovskite absorber layer, improving the quality of the perovskite thin film, optimizing the optical design of the device, and reducing reflection and parasitic absorption.

[0004] For silicon / perovskite / perovskite triple-junction photovoltaic devices where the bandgap of the wide-bandgap perovskite top cell and the silicon substrate cell are essentially determined, the silicon substrate cell has a fixed bandgap and primarily absorbs long-wavelength photons transmitted through the top two sub-cells. The middle perovskite sub-cell absorbs mid-to-long-wavelength light between the transmission region of the wide-bandgap perovskite top cell and the strong absorption region of the silicon substrate cell. Since the sub-cells of the triple-junction photovoltaic device operate in series, the current output must be determined by the sub-cell with the smallest current. When the long-wavelength response of the middle perovskite sub-cell is insufficient, it easily becomes the limiting sub-cell restricting the overall device's output current; that is, the spectral response of the middle sub-cell directly determines the upper limit of the series current of the entire device.

[0005] However, when the intermediate perovskite sub-cell fails to absorb sufficiently near the cutoff edge, or when its internal carrier diffusion length and interface extraction capability are insufficient to support effective collection, these mid-to-long-wavelength photons are difficult to convert into effective photocurrent in the intermediate perovskite sub-cell. Instead, they continue to pass through and be absorbed by the silicon substrate sub-cell, resulting in a mismatch where the integrated photocurrent of the intermediate perovskite sub-cell is low, while the silicon substrate sub-cell still retains a higher photocurrent. Since the residual current of the silicon substrate sub-cell cannot be output independently in the series structure, the operating current of the entire device is still limited by the intermediate perovskite sub-cell.

[0006] Furthermore, simply relying on bandgap or thickness control to increase the current of the intermediate perovskite sub-cell is insufficient to fully address the aforementioned mismatch problem. While reducing the bandgap of the intermediate perovskite sub-cell can shift the absorption edge towards longer wavelengths, thereby expanding the utilization range of mid- and long-wavelength photons, this process typically depends on adjusting the halogen composition, metal cations, or organic cation ratios. This often simultaneously alters the material's energy level positions, crystallization kinetics, defect formation energy, and phase stability, introducing new non-radiative recombination losses. Increasing the thickness of the intermediate perovskite absorption layer can improve the absorption probability of weakly absorbed photons near the bandgap, but under thick-film conditions, carriers generated by these photons tend to be generated at deeper locations, requiring longer transport distances for collection by the electrodes, thus increasing the probability of bulk and interfacial recombination. Therefore, the above methods have limited ability to compensate for specific long-wavelength response gaps near the cutoff edge, making it difficult to achieve precise current control while maintaining effective carrier collection and not significantly affecting the light incidence of the underlying silicon substrate sub-cell.

[0007] Therefore, the insufficient long-wavelength response of the intermediate perovskite sub-cell and the current mismatch between it and the silicon substrate sub-cell become key factors limiting the further improvement of the series output current of triple-junction stacked devices.

[0008] Therefore, how to compensate for the long-wavelength current gap of conventional bandgap perovskite intermediate cells without significantly reducing the long-wavelength response of silicon substrate cells, so that the integrated photocurrent of the intermediate cell can enter the current window that matches the top cell, and improve the series confinement current of triple junction stacked devices, is a technical problem that needs to be solved in this field. Summary of the Invention

[0009] To address the insufficient spectral response of conventional bandgap perovskite intermediate cells in the long-wavelength region, resulting in lower integrated photocurrents in the intermediate cells compared to the top and silicon substrate cells, thus making them series-confined cells; and the difficulty in simultaneously achieving long-wavelength current compensation for the intermediate cells and long-wavelength photon retention in the silicon substrate cell by reducing the bandgap of the intermediate perovskite or increasing the thickness of the perovskite absorber layer, this invention provides a current-matched enhanced silicon-calcium-calcium triple-junction photovoltaic device and its fabrication method, achieving long-wavelength gap compensation for the intermediate cells, long-wavelength response retention in the silicon substrate cell, and improved current matching in the triple-junction device.

[0010] The technical solution adopted in this invention is as follows:

[0011] A current-matching enhanced silicon-calcium-calcium triple junction photovoltaic device includes a silicon substrate cell, an intermediate cell, and a wide-bandgap perovskite top cell stacked sequentially from bottom to top. The intermediate cell includes a conventional bandgap perovskite main absorber layer, a passivation layer, and an organic heterojunction compensation layer stacked sequentially from bottom to top.

[0012] Among them, the organic heterojunction compensation layer is used to compensate for the photocurrent gap of the mesocell in the 780 nm~900 nm band, so as to enhance the external quantum efficiency response of the mesocell in the 780 nm~900 nm band and extend the equivalent EQE cutoff edge of the mesocell to the long wavelength direction.

[0013] Furthermore, the silicon substrate cell is a silicon heterojunction solar cell.

[0014] Furthermore, the band gap of the wide-bandgap perovskite top cell is 1.85 eV to 2.05 eV, preferably 1.90 eV to 1.95 eV.

[0015] Furthermore, the band gap of the conventional bandgap perovskite main absorber layer is 1.50 eV to 1.65 eV, preferably 1.50 eV to 1.55 eV.

[0016] Furthermore, the passivation layer is selected based on the material composition and surface state of the conventional bandgap perovskite main absorber layer and the film-forming compatibility of the organic heterojunction compensation layer, in order to improve the interfacial film-forming conditions of the organic heterojunction compensation layer on the surface of the conventional bandgap perovskite main absorber layer.

[0017] Furthermore, the material of the passivation layer is an organic ammonium salt passivation material, selected from one or more combinations of alkyl diamine iodides (such as PDAI2, EDAI2, BDAI2), heterocyclic ammonium iodides (such as PDI, PI and their derivatives), and aromatic ammonium salts (such as 3MTPAI, PEAI).

[0018] Furthermore, the organic heterojunction compensation layer is a bulk heterojunction structure formed by an organic donor material and an organic acceptor material; wherein the organic donor material is a D18 series material and the organic acceptor material is Y6.

[0019] Furthermore, by changing the material composition, donor-acceptor mass ratio, and thickness of the organic heterojunction compensation layer, the target spectral response of the mesocell can be modulated, thereby achieving selective compensation for the long-wavelength photocurrent gap of the mesocell.

[0020] Furthermore, the mass ratio of the organic donor material to the organic acceptor material is 1:1.2~1.4.

[0021] Furthermore, the thickness of the organic heterojunction compensation layer is 40 nm to 60 nm, preferably 50 nm.

[0022] Furthermore, the current-matched enhanced silicon-calcium-calcium triple-junction photovoltaic device also includes a lower interconnect layer located between the silicon substrate cell and the intermediate cell, and an upper interconnect layer located between the intermediate cell and the wide-bandgap perovskite top cell.

[0023] Furthermore, the lower interconnect layer includes an ITO layer and a hole transport layer stacked sequentially from bottom to top.

[0024] Furthermore, the upper interconnect layer includes an electron transport layer, an ITO layer, and a hole transport layer stacked sequentially from bottom to top.

[0025] Furthermore, the wide-bandgap perovskite top cell includes a wide-bandgap perovskite absorber layer, a passivation layer, an electron transport layer, and an electrode layer stacked sequentially from bottom to top.

[0026] Furthermore, the organic heterojunction compensation layer enables the equivalent EQE cutoff edge of the hybrid intermediate cell to be located at 850 nm to 900 nm, preferably 860 nm.

[0027] Furthermore, under AM 1.5G standard solar spectral conditions, the organic heterojunction compensation layer increases the integrated photocurrent density of the hybrid intermediate cell by no less than 0.8 mA / cm², preferably by no less than 1.0 mA / cm²; the organic heterojunction compensation layer reduces the integrated photocurrent density of the silicon substrate cell by no more than 0.5 mA / cm², preferably by no more than 0.2 mA / cm²; and the organic heterojunction compensation layer increases the series confinement current of the current-matched enhanced silicon-calcium-calcium triple-junction photovoltaic device by no less than 0.5 mA / cm², preferably by no less than 1.0 mA / cm².

[0028] The method for fabricating the current-matched enhanced silicon-calcium triple-junction photovoltaic device includes the following steps:

[0029] Step 1: Fabricate the lower interconnect layer above the silicon substrate solar cell;

[0030] Step 2: Prepare a conventional bandgap perovskite precursor solution, spin-coat it onto the upper surface of the lower interconnect layer, and anneal it to form a conventional bandgap perovskite main absorber layer;

[0031] Step 3: Form a passivation layer on the upper surface of a conventional bandgap perovskite main absorber layer;

[0032] Step 4: Prepare an organic heterojunction precursor solution containing organic donor and organic acceptor materials, spin-coat it onto the upper surface of the passivation layer, and anneal it to form an organic heterojunction compensation layer, which together with the passivation layer and the conventional bandgap perovskite main absorber layer constitutes an intermediate sub-cell.

[0033] Step 5: Fabricate an interconnect layer above the intermediate sub-cell;

[0034] Step 6: Prepare a wide-bandgap perovskite precursor solution, spin-coat it onto the upper surface of the upper interconnect layer, and anneal it to form a wide-bandgap perovskite top cell, thereby obtaining a current-matched enhanced silicon-calcium-calcium triple junction photovoltaic device.

[0035] Furthermore, the specific process of step 2 is as follows:

[0036] FAI, CsI, PbI₂, and PbCl₂ were dissolved in a mixed solvent of DMF (N,N-dimethylformamide) and NMP (N-methyl-2-pyrrolidone) in a molar ratio of approximately 1.5–1.9:0.1–0.5:1.8–2.2:0.1–0.8 to prepare a 1.6–1.8 M FAI solution. 0.9 Cs 0.1 The PbI3 perovskite precursor solution was spin-coated onto the upper surface of the lower interconnect layer at a speed of 2000~5000 rpm for 40~50s, and gas quenching was started 10~20s after the spin coating began until the spin coating was completed; then it was annealed at 100~150℃ for 10~20 min to form a conventional bandgap perovskite main absorber layer.

[0037] Furthermore, the specific process of step 3 is as follows:

[0038] PDAI2 was dissolved in IPA to form a passivation solution with a concentration of 0.5~1.5 mg / mL. The solution was spin-coated onto the surface of a conventional bandgap perovskite main absorber layer at a speed of 4000~6000 rpm for 20~40 s. The solution was then annealed at 80~110℃ for 5~10 min to form a passivation layer.

[0039] Furthermore, the specific process of step 4 is as follows:

[0040] Dissolve 2-4 mg / mL of organic donor material D18-Cl and 3-5 mg / mL of organic acceptor material Y6 in CHCl3 to prepare an organic heterojunction precursor solution with a solute concentration of 5-9 mg / mL. Spin-coat the solution onto the surface of the passivation layer at 1500-2500 rpm for 20-40 s, and then anneal at 80-100℃ for 8-12 min to form an organic heterojunction compensation layer.

[0041] Compared with existing technologies, the beneficial effects of the current-matching enhanced silicon-calcium-calcium triple-junction photovoltaic device and its fabrication method proposed in this invention are as follows:

[0042] 1. Unlike conventional perovskite intermediate cells in traditional silicon-calcium-calcium triple-junction photovoltaic devices, this invention employs an intermediate cell comprising a conventional perovskite main absorber layer, a passivation layer, and an organic heterojunction compensation layer. By adjusting the material composition, donor-acceptor mass ratio, and thickness of the organic heterojunction compensation layer, selective compensation is achieved for the photocurrent gap in the 780–900 nm band of conventional perovskite intermediate cells, resulting in a photocurrent increment of not less than 1.06 mA / cm², accounting for approximately 88.3% of the total current increment of 1.20 mA / cm². Simultaneously, the equivalent EQE cutoff edge of the intermediate cell is extended from approximately 810 nm to approximately 860 nm, corresponding to an extension of the cutoff energy from approximately 1.53 eV to approximately 1.44 eV. This indicates that the intermediate cell achieves a longer equivalent spectral response while maintaining the conventional bandgap range of the conventional perovskite main absorber layer.

[0043] 2. Compared with traditional silicon-calcium-calcium triple-junction photovoltaic devices that use the middle perovskite sub-cell as the confining sub-cell, this invention significantly increases the integrated photocurrent density of the middle sub-cell, allowing the middle sub-cell to exit the series confining position of the triple-junction device, and uses the wide-bandgap perovskite top sub-cell as the confining sub-cell. This not only increases the series confining current of the device, but also helps to increase the total open-circuit voltage of the entire device, providing a new approach to improving the overall performance of the device.

[0044] 3. While increasing the integrated photocurrent of the intermediate subcell, this invention has little impact on the long-wavelength response of the silicon substrate subcell. The integrated photocurrent of the silicon substrate subcell decreases by only 0.09 mA / cm², and the ratio of the loss of the silicon substrate subcell to the increase of the intermediate subcell is 7.5%. This improves the mismatch between the low integrated photocurrent of the intermediate perovskite subcell and the high photocurrent of the silicon substrate subcell.

[0045] 4. When the thickness of the organic heterojunction compensation layer described in this invention is between 40 nm and 60 nm, the photocurrent of the intermediate subcell is compensated and the current loss of the silicon substrate subcell is small. When the thickness continues to increase, although the photocurrent of the intermediate subcell continues to increase, the series limiting current no longer increases, and the integrated photocurrent of the silicon substrate subcell decreases more sharply. Therefore, the technical effect of this invention comes from the synergistic relationship between specific band compensation, compensation layer thickness and three-subcell current matching.

[0046] 5. The intermediate cell proposed in this invention has a simple structure and is easy to prepare. A C60 layer can be directly deposited on it without the need for other organic functional layers. This helps to reduce the risk of interface disturbance, residual solvent influence and film layer mutual solubility that may be caused by the superposition of multiple organic film layers. Attached Figure Description

[0047] Figure 1This is a schematic diagram of the current-matching enhanced silicon-calcium-calcium triple-junction photovoltaic device proposed in Example 1;

[0048] Figure 2 The equivalent circuit diagram of the traditional silicon-calcium-calcium triple junction photovoltaic device in Comparative Example 1 is shown.

[0049] Figure 3 This is a schematic diagram of the equivalent circuit of the current-matching enhanced silicon-calcium-calcium triple-junction photovoltaic device proposed in Example 1;

[0050] Figure 4 A comparison graph of the JV curves of the devices obtained in Comparative Example 1 and Example 1;

[0051] Figure 5 The EQE curves and integrated photocurrent of each sub-cell are shown in the comparison diagram between the devices obtained in Comparative Example 1 and Example 1.

[0052] Figure 6 The dEQE curves are for the intermediate subcells of the devices obtained in Comparative Example 1 and Example 1. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0054] Example 1

[0055] This embodiment proposes a current-matching enhanced silicon-calcium-calcium triple-junction photovoltaic device, the structure of which is as follows: Figure 1 As shown, it includes a silicon substrate cell, a lower interconnect layer, an intermediate cell, an upper interconnect layer, and a wide-bandgap perovskite top cell stacked sequentially from bottom to top.

[0056] The silicon substrate cell is a silicon heterojunction solar cell.

[0057] The lower interconnect layer includes an ITO layer and a hole transport layer stacked sequentially from bottom to top; wherein, the hole transport layer is made of NiO. X It consists of a nanoparticle layer and a carbazole-based self-assembled monolayer.

[0058] The intermediate sub-cell comprises, from bottom to top, a conventional bandgap perovskite main absorber layer, a passivation layer, and an organic heterojunction compensation layer; wherein, the organic heterojunction compensation layer is a bulk heterojunction structure formed by organic donor material D18-Cl and organic acceptor material Y6, with a thickness of 50 nm; the passivation layer is made of PDAI2; and the conventional bandgap perovskite main absorber layer is made of FA. 0.9 Cs 0.1 PbI3 has a band gap of 1.53 eV.

[0059] The upper interconnect layer comprises, from bottom to top, a C60 layer, a SnO2 layer, an ITO layer, and a hole transport layer; wherein, the hole transport layer is composed of NiO X It consists of a nanoparticle layer and a carbazole-based self-assembled monolayer.

[0060] The wide-bandgap perovskite top solar cell comprises, from bottom to top, a wide-bandgap perovskite absorber layer, a passivation layer, a C60 electron transport layer, a SnO2 layer, an IZO transparent conductive layer, and an Ag electrode layer; wherein, the material of the wide-bandgap perovskite absorber layer is Cs. 0.25 FA 0.60 MA 0.15 Pb(I 0.43 Br 0.57 )3, with a band gap of 1.93 eV.

[0061] The fabrication process of the current-matched enhanced silicon-calcium triple-junction photovoltaic device includes the following steps:

[0062] Step A, silicon substrate cell processing and lower interconnect layer fabrication, specifically includes:

[0063] A 4-inch silicon wafer with a silicon heterojunction structure is cut into small-area devices of 2.5 cm × 2.5 cm to serve as silicon-based solar cells;

[0064] An ITO film with a thickness of approximately 10 nm was deposited on the surface of a silicon substrate cell using magnetron sputtering as part of the second interconnect layer between the silicon substrate cell and the intermediate cell cell. The substrate with the deposited ITO film was then ultrasonically cleaned in acetone and isopropanol for 30 min each time. Subsequently, the substrate was surface treated with plasma.

[0065] Subsequently, NiO was deposited on top of the ITO thin film using magnetron sputtering. X Nanoparticle layer on NiO X Carbazole-based self-assembled monolayers are formed on the surface of the nanoparticle layer. Specifically, 4PADCB is dissolved in anhydrous ethanol to prepare a solution with a concentration of about 1 mg / mL. The solution is then spin-coated at 4000 rpm for 30 s and annealed at 100℃ for 10 min to form a carbazole-based self-assembled monolayer. This is then used to prepare the lower interconnect layer on top of the silicon substrate solar cell.

[0066] Step B: Fabricate an intermediate sub-cell above the lower interconnect layer, specifically as follows:

[0067] Step B1: Dissolve FAI (309.6 mg), CsI (52 mg), PbI2 (922 mg), and PbCl2 (55.6 mg) in a mixed solvent of DMF and NMP at a volume ratio of 960:150 to prepare a 1.8 M FAI solution. 0.9 Cs 0.1 A conventional bandgap perovskite precursor solution of PbI3 was spin-coated onto the surface of the lower interconnect layer at 5000 rpm for 50 s, and gas quenching was started 10 s after spin-coating until the spin-coating was completed; then it was annealed at about 150 ℃ for about 10 min to form a conventional bandgap perovskite main absorber layer.

[0068] Step B2: Dissolve PDAI2 in IPA to form a passivation solution with a concentration of 1 mg / mL. Spin-coat the solution onto the surface of a conventional bandgap perovskite main absorber layer at 5000 rpm for 30 s. Then anneal at 100 ℃ for 10 min to obtain the passivation layer.

[0069] Step B3: Dissolve 3 mg / mL of organic donor material D18-Cl and 4 mg / mL of organic acceptor material Y6 in CHCl3 to prepare an organic heterojunction precursor solution with a solute concentration of 7 mg / mL; spin-coat the solution onto the passivation layer surface at 2000 rpm for 30 s, and then anneal at 85 °C for 10 min to form an organic heterojunction compensation layer with a thickness of 50 nm. The conventional bandgap perovskite main absorber layer, PDAI2 passivation layer, and organic heterojunction compensation layer together constitute the intermediate sub-cell.

[0070] Step C: Fabricate an interconnect layer above the intermediate sub-cell, specifically as follows:

[0071] A 15 nm C60 layer was first thermally vaporized on the surface of the intermediate cell, followed by an ALD (atomic layer deposition) deposition of a 15 nm SnO2 layer, and then a 10 nm ITO thin film was magnetron sputtered.

[0072] Subsequently, a 10 mg / mL aqueous dispersion of NiOx nanoparticles was spin-coated onto the surface of an ITO film at 4000 rpm for 30 s, followed by annealing in air at 100 °C for 10 min to form NiO. X Nanoparticle layer; then, 2PACz and MeO-2PACz are mixed at a mass ratio of 3:1 and dissolved in anhydrous ethanol to form a solution with a concentration of 1 mg / mL. This solution is then spin-coated onto NiO at 4000 rpm for 30 s. X The surface of the nanoparticle layer is annealed at 100 °C for 10 min to form a carbazole-based self-assembled monolayer, thereby completing the preparation of the upper interconnect layer.

[0073] Step D: Fabricate a wide-bandgap perovskite top cell above the upper interconnect layer, specifically as follows:

[0074] Step D1: Dissolve FAI (103 mg), CsI (65 mg), MABr (17 mg), PbBr2 (304 mg), and PbI2 (87.6 mg) in 1 mL of a mixed solvent with a volume ratio of 3:1 (i.e., 750 μL DMF / 250 μL DMSO) to prepare 1 M CsI. 0.25 FA 0.60 MA 0.15 Pb(I 0.43 Br 0.57 A wide-bandgap perovskite precursor solution was prepared and coated onto the surface of the upper interconnect layer using a two-step spin-coating method. First, the solution was spin-coated at 1000 rpm for 10 s, and then at 6000 rpm for 45 s. 15 s before the end of the spin-coating, 200 µL of EA (ethyl acetate) was added dropwise. The solution was then annealed at 100 °C for 20 min to form a wide-bandgap perovskite absorber layer.

[0075] Step D2: Prepare an IPA (isopropanol) solution of EDAI2 (ethylenediamine dihydroiodide) with a concentration of 1 mg / mL as a surface passivation treatment solution. Spin-coat the solution onto the surface of the wide-bandgap perovskite absorber layer at 5000 rpm for 30 s and anneal at 100℃ for 5 min to obtain the passivation layer.

[0076] Step D3: On top of the passivation layer, a 20 nm C60 thin film is first thermally evaporated, followed by an ALD deposition of a 15 nm SnO2 thin film, then a 50 nm IZO transparent conductive layer is magnetron sputtered, and finally an Ag electrode layer with a thickness of 400 nm is thermally evaporated to complete the fabrication of a wide-bandgap perovskite top cell, thus obtaining a current-matched enhanced silicon-calcium-calcium triple junction photovoltaic device.

[0077] Comparative Example 1

[0078] This comparative example presents a conventional silicon-calcium-calcium triple junction photovoltaic device. Its structure differs from that of Example 1 only in that the intermediate cell does not have a passivation layer and an organic heterojunction compensation layer; the other structures and preparation processes are the same.

[0079] The performance of the current-matched enhanced silicon-calcium-calcium triple-junction photovoltaic device (referred to as NewStructure) obtained in Example 1 and the conventional silicon-calcium-calcium triple-junction photovoltaic device (referred to as Conventional Structure) obtained in Comparative Example 1 are compared below.

[0080] 1) EQE Test Comparison

[0081] The current-matched enhanced silicon-calcium-calcium triple-junction photovoltaic device obtained in Example 1 and the conventional silicon-calcium-calcium triple-junction photovoltaic device obtained in Comparative Example 1 were subjected to EQE tests, and the integrated photocurrent density of each sub-cell was obtained by integrating according to the AM 1.5G standard solar spectrum. The EQE curves are shown below. Figure 5 As shown, the integrated photocurrent density data of the sub-cells of the two devices are summarized in Table 1:

[0082] Table 1

[0083]

[0084] As shown in Table 1, the integrated photocurrent of the intermediate sub-cell in Comparative Example 1 is 11.55 mA / cm², which is lower than that of the top sub-cell and the silicon substrate sub-cell. Therefore, the intermediate sub-cell is a series-confined sub-cell. In Example 1, the integrated photocurrent of the intermediate sub-cell is increased to 12.75 mA / cm², an increase of 1.20 mA / cm² compared to the intermediate sub-cell in Comparative Example 1; the integrated photocurrent of the top sub-cell is 12.62 mA / cm², and the integrated photocurrent of the silicon substrate sub-cell is 13.86 mA / cm². Therefore, the confined sub-cell in Example 1 is changed from the intermediate sub-cell of Comparative Example 1 to the top sub-cell, and the series confining current is increased from 11.55 mA / cm² to 12.62 mA / cm².

[0085] based on Figure 5 The EQE data of the intermediate sub-cell shown are obtained after differentiation. Figure 6 The dEQE curves shown are used to extract the wavelengths at each inflection point to obtain the EQE cutoff information of the intermediate sub-cell, as shown in Table 2.

[0086] Table 2

[0087]

[0088] As shown in Table 2, the equivalent EQE cutoff edge of the intermediate cell in Comparative Example 1 is about 810 nm, while the equivalent EQE cutoff edge of the intermediate cell in Example 1 extends to about 860 nm. This indicates that, under the premise that the intermediate main absorption layer still uses conventional bandgap perovskite material, by introducing an organic heterojunction compensation layer to compensate for the long-wavelength spectral response gap, the equivalent spectral response of the intermediate cell can be extended to the long-wavelength direction.

[0089] 2) Comparison of photocurrent contributions of intermediate subcells in different wavelength bands

[0090] based on Figure 5 The EQE curves of the intermediate cell are shown in Table 3. The photocurrent contributions of different wavelength bands are integrated according to the AM 1.5G standard solar spectrum.

[0091] Table 3

[0092]

[0093] As shown in Table 3, the integrated photocurrent of the intermediate cell in Comparative Example 1 is 11.55 mA / cm², and the integrated photocurrent of the intermediate cell in Example 1 is 12.75 mA / cm². By introducing an organic heterojunction compensation layer, the incremental photocurrent ΔJ of the intermediate cell is increased. mid = 12.75 − 11.55 = 1.20 mA / cm².

[0094] Specifically, in the 780 nm to 900 nm wavelength range, the photocurrent contributions of the intermediate cell in Comparative Example 1 and Example 1 were 1.20 mA / cm² and 2.26 mA / cm², respectively, and the photocurrent increment ΔJ in this wavelength range was... 780~900 = 2.26 − 1.20 = 1.06 mA / cm², therefore, the proportion of the photocurrent increment in the 780 nm to 900 nm band to the total photocurrent increment of the mesocell is: 1.06 / 1.20 × 100% = 88.3%. This indicates that the increase in the integrated photocurrent of the mesocell mainly comes from the 780 nm to 900 nm band, while the current increments in the 350 nm to 780 nm and 900 nm to 1100 nm bands are relatively small.

[0095] The above results indicate that the introduced organic heterojunction compensation layer mainly compensates for the long-wavelength photocurrent gap of conventional bandgap perovskite meson cells in the 780 nm to 900 nm range, rather than relying primarily on non-selective absorption enhancement across the entire wavelength range.

[0096] 3) Comparison of compensation effectiveness

[0097] Based on the integrated photocurrent density data shown in Table 1, it can be seen that the change in current of the silicon substrate cell in Example 1 compared to Comparative Example 1 is ΔJ. Si = 13.86 - 13.95 = -0.09 mA / cm², the series limiting current increment is ΔJ lim =12.62 - 11.55 = 1.07 mA / cm².

[0098] To evaluate the compensation effect of the organic heterojunction compensation layer on the intermediate cell, the compensation effectiveness factor ηcomp is defined as the ratio of the absolute value of the integral photocurrent increment of the intermediate cell to the absolute value of the integral photocurrent loss of the silicon substrate cell, i.e., ηcomp = ΔJmid / |ΔJSi| = 1.20 / 0.09 = 13.33.

[0099] Further calculations show that the ratio of current loss in the silicon substrate cell to the integral photocurrent increment in the intermediate cell is |ΔJSi| / ΔJmid × 100% = 0.09 / 1.20 × 100% = 7.5%.

[0100] The above calculation results show that, in Example 1, by setting the organic heterojunction compensation layer, the integrated photocurrent of the intermediate cell increased by 1.20 mA / cm², and the series confinement current increased by 1.07 mA / cm², while the integrated photocurrent of the silicon substrate cell decreased by only 0.09 mA / cm². The current loss of the silicon substrate cell accounts for only 7.5% of the current increase of the intermediate cell, indicating that the organic heterojunction compensation layer can significantly improve the integrated photocurrent of the intermediate cell while having a minimal impact on the long-wavelength photocurrent response of the silicon substrate cell. Therefore, the organic heterojunction compensation layer of Example 1 has high compensation effectiveness, capable of compensating for the long-wavelength photocurrent gap of the intermediate cell while also ensuring the long-wavelength photon utilization of the silicon substrate cell.

[0101] 4) The effect of the thickness of the organic heterojunction compensation layer in Example 1

[0102] To analyze the impact of the organic heterojunction compensation layer thickness on the current matching of silicon-calcium-calcium triple-junction photovoltaic devices, relevant tests were conducted on the organic heterojunction compensation layer thickness based on the actual layer sequence, EQE response range, and AM 1.5G standard solar spectrum. By varying the organic heterojunction compensation layer thickness, the integrated photocurrent of the top cell, the integrated photocurrent of the middle cell, the integrated photocurrent of the silicon substrate cell, and the series confinement current were calculated. The results are shown in Table 4.

[0103] Table 4

[0104]

[0105] As shown in Table 4, when the thickness of the organic heterojunction compensation layer increases from 0 nm to 50 nm, the integrated photocurrent of the intermediate subcell changes from 11.55 mA / cm² to 12.75 mA / cm²; the series confinement current changes from 11.55 mA / cm² to 12.62 mA / cm²; and the integrated photocurrent of the silicon substrate subcell changes from 13.95 mA / cm² to 13.86 mA / cm². Simultaneously, the confinement subcell functions as an intermediate subcell when the thickness is 0–40 nm, and transforms into a top subcell for the first time at a thickness of 50 nm. When the thickness of the organic heterojunction compensation layer was further increased to 60 nm, 80 nm and 100 nm, the integrated photocurrent of the intermediate cell continued to increase (reaching 12.84, 12.94 and 13.02 mA / cm², respectively), but the series confinement current no longer increased (to 12.60, 12.57 and 12.54 mA / cm², respectively), and the integrated photocurrent of the silicon substrate cell decreased more sharply (to 13.80, 13.68 and 13.52 mA / cm², respectively).

[0106] The above results indicate that the preferred thickness of the organic heterojunction compensation layer is 40 nm to 60 nm, more preferably 50 nm. This is because when the compensation layer thickness is 50 nm, the integrated photocurrent of the intermediate subcell just exceeds that of the top subcell, causing the confined subcell to transition from the intermediate subcell to the top subcell, and the series confinement current reaches a turning point (12.62 mA / cm²). Further thickening the organic heterojunction compensation layer can further increase the intermediate subcell current, but it exacerbates the parasitic absorption of long-wavelength photons from the silicon substrate subcell, resulting in a decrease in the series confinement current instead of an increase. This shows that Example 1 does not achieve indiscriminate absorption by arbitrarily increasing the thickness of the organic heterojunction compensation layer, but rather has a confined compensation port that balances intermediate subcell gap compensation and long-wavelength photon retention in the silicon substrate subcell.

[0107] 5) JV Test Comparison

[0108] Figure 4 The JV curves of the devices obtained in Comparative Example 1 and Example 1 are compared. It can be seen that the current density plateau of Example 1 is higher than that of Comparative Example 1. Combining the EQE integration results in Table 1, the series limiting current of Comparative Example 1 is 11.55 mA / cm², and the series limiting current of Example 1 is 12.62 mA / cm². This shows that the current increase trend of the JV curve is consistent with the EQE integration results, indicating that the long-wavelength response compensation of the intermediate sub-cell generated after introducing the organic heterojunction compensation layer can be converted into an effective series output current increase of the triple-junction tandem photovoltaic device.

[0109] Based on the performance data of the conventional silicon-calcium-calcium triple-junction photovoltaic device obtained in Comparative Example 1 and the current-matching enhanced silicon-calcium-calcium triple-junction photovoltaic device obtained in Example 1, the following are established: Figure 2 and 3 The equivalent circuit model is shown. In the model, each photovoltaic sub-cell is represented by a photocurrent source Jph, a diode D, a parallel resistor Rsh, and a series resistor Rs; where Jph represents the photocurrent generated by the corresponding sub-cell under illumination, D represents the diode characteristics of the photovoltaic junction, and Rsh and Rs represent the parallel loss and series resistance, respectively.

[0110] like Figure 2 As shown, the equivalent circuit model of Comparative Example 1 consists of three sub-cell branches connected in series along the current direction. Figure 3 As shown, although the equivalent circuit model of Example 1 also consists of three sub-cell branches connected in series along the current direction, the branch corresponding to the intermediate sub-cell is represented by two equivalent photocurrent response branches connected in parallel: one represents the photocurrent of the conventional bandgap perovskite main absorber layer, and the other represents the compensation photocurrent generated by the organic heterojunction compensation layer in a specific long-wavelength band. The two branches jointly characterize the photocurrent response of the intermediate sub-cell, but no independent interconnection layer is set between them, and the organic heterojunction compensation layer does not constitute an independent organic sub-cell.

[0111] Figure 3 The equivalent circuit diagram shown is established based on the following:

[0112] (1) Physical structure determines topological connection: Only a few nanometers thick PDAI2 passivation layer is set between the conventional bandgap perovskite main absorber layer and the organic heterojunction compensation layer. This passivation layer is only used to improve the interfacial film formation conditions and does not have the function of carrier recombination or tunneling connection. The necessary prerequisite for the voltage superposition of two independent pn junctions is to set a heavily doped tunnel junction or a transparent conductive oxide interconnect layer to complete the efficient recombination of carriers. Since no such interconnect layer is set in Example 1, the organic heterojunction compensation layer does not have the electrical conditions for voltage superposition with the conventional bandgap perovskite main absorber layer. The two cannot be independently connected in series at the equivalent circuit level, and thus belong to the current contribution branch of the same output port, that is, the photocurrent is superimposed in parallel in the equivalent circuit.

[0113] (2) Spectral response determines the branch contribution method: Table 3 shows that the EQE band-wise integration shows that the total current increment of the intermediate sub-cell in Example 1 is 1.20 mA / cm², of which the increment in the 800~900 nm band reaches 1.06 mA / cm², accounting for 88.3% of the total increment. This indicates that the organic heterojunction compensation layer does not absorb the full spectrum, but mainly selectively compensates for the long-wave gap after the cutoff edge (about 810 nm) of the conventional bandgap perovskite main absorber layer. Therefore, its corresponding equivalent branch should be a specific band compensation branch, rather than an independent sub-cell with a complete spectral response. At the same time, Table 2 shows that the equivalent EQE cutoff edge extends from 810 nm to 860 nm, while the bandgap of the conventional bandgap perovskite main absorber layer remains unchanged (still 1.53 eV), further indicating that the long-wave response originates from the current superposition within the same node, rather than the appearance of the cutoff edge of an independent sub-cell.

[0114] (3) Verification of the rationality of the electrical output model: Figure 4 The JV test results show that the overall current (intercept with the Y-axis) of the device in Example 1 is significantly improved compared to Comparative Example 1, but there is no step increase in voltage (intercept with the X-axis) due to the addition of the pn junction. If the organic heterojunction compensation layer constitutes an independent organic sub-cell, then the triple-junction device essentially becomes a quadruple-junction series device, and its open-circuit voltage should be approximately the sum of the open-circuit voltages of the four sub-cells, which is inconsistent with the JV results. Therefore, the role of the organic heterojunction compensation layer is more consistent with the situation of current compensation within the framework of a triple-junction device. Based on the above structural, spectral, and electrical evidence, Figure 3 The two branches within the dashed box only represent the superposition relationship of different spectral response sources in the equivalent photocurrent; they do not indicate that an independent interconnect layer is set between them, nor do they indicate that the organic heterojunction compensation layer constitutes an independent organic sub-cell. Furthermore, the intermediate sub-cell, as an intermediate photovoltaic functional unit, is connected in series with the wide-bandgap perovskite top cell and the silicon substrate cell.

[0115] Based on the equivalent circuit and data results described above, the intermediate sub-cell in Comparative Example 1, due to insufficient long-wavelength response, has an integrated photocurrent of 11.55 mA / cm², thus becoming a series-confined sub-cell. Example 1, by introducing an organic heterojunction compensation layer, increases the integrated photocurrent of the intermediate sub-cell by 1.20 mA / cm², increases the series-confined current by 1.07 mA / cm², while the integrated photocurrent of the silicon substrate sub-cell decreases by only 0.09 mA / cm². Therefore, Figure 3 The equivalent circuit of the hybrid intermediate cell shown accurately reflects the technical essence of the intermediate cell in Example 1: the organic heterojunction compensation layer serves as a non-independent photocurrent compensation channel inside the intermediate cell, working together with the conventional bandgap perovskite main absorber layer to improve the long-wavelength response of the intermediate cell without forming an additional independent organic cell.

[0116] It should be noted that this is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A current-matched enhanced silicon-calcium-calcium triple-junction photovoltaic device, characterized in that, It includes a silicon substrate cell, an intermediate cell, and a wide bandgap perovskite top cell stacked from bottom to top. The intermediate cell includes a conventional bandgap perovskite main absorber layer, a passivation layer, and an organic heterojunction compensation layer stacked from bottom to top. Among them, the organic heterojunction compensation layer is used to compensate for the photocurrent gap of the mesocell in the 780 nm~900 nm band, so as to enhance the external quantum efficiency response of the mesocell in this band and extend the equivalent EQE cutoff edge of the mesocell to the long wavelength direction.

2. The current-matched enhanced silicon-calcium-calcium triple-junction photovoltaic device according to claim 1, characterized in that, The silicon substrate cell is a silicon heterojunction solar cell; the band gap of the wide bandgap perovskite top cell is 1.85 eV~2.05 eV; the band gap of the conventional bandgap perovskite main absorber layer is 1.50 eV~1.65 eV.

3. The current-matched enhanced silicon-calcium-calcium triple-junction photovoltaic device according to claim 1, characterized in that, The organic heterojunction compensation layer is a bulk heterojunction structure formed by organic donor material and organic acceptor material; wherein, the organic donor material is a D18 series material and the organic acceptor material is Y6.

4. The current-matched enhanced silicon-calcium-calcium triple-junction photovoltaic device according to claim 3, characterized in that, By changing the material composition, donor-acceptor mass ratio, and thickness of the organic heterojunction compensation layer, the target spectral response of the mesocell can be modulated, thereby achieving selective compensation for the long-wavelength photocurrent gap of the mesocell.

5. The current-matched enhanced silicon-calcium-calcium triple-junction photovoltaic device according to claim 4, characterized in that, The mass ratio of the organic donor material to the organic acceptor material is 1:1.2~1.

4.

6. The current-matched enhanced silicon-calcium-calcium triple-junction photovoltaic device according to claim 4, characterized in that, The thickness of the organic heterojunction compensation layer is 40 nm to 60 nm.

7. The current-matched enhanced silicon-calcium-calcium triple-junction photovoltaic device according to claim 1, characterized in that, The passivation layer is made of organic ammonium salt passivation material, specifically one or more combinations of alkyl diamine iodide, heterocyclic ammonium iodide, and aromatic ammonium salt.

8. The current-matched enhanced silicon-calcium-calcium triple-junction photovoltaic device according to claim 7, characterized in that, The current-matched enhanced silicon-calcium-calcium triple junction photovoltaic device also includes a lower interconnect layer located between the silicon substrate cell and the intermediate cell, and an upper interconnect layer located between the intermediate cell and the wide-bandgap perovskite top cell.

9. A method for fabricating a current-matched enhanced silicon-calcium-calcium triple-junction photovoltaic device, characterized in that, Includes the following steps: Step 1: Fabricate the lower interconnect layer above the silicon substrate solar cell; Step 2: Prepare a conventional bandgap perovskite precursor solution, spin-coat it onto the upper surface of the lower interconnect layer, and anneal it to form a conventional bandgap perovskite main absorber layer; Step 3: Form a passivation layer on the upper surface of a conventional bandgap perovskite main absorber layer; Step 4: Prepare an organic heterojunction precursor solution containing organic donor and organic acceptor materials, spin-coat it onto the upper surface of the passivation layer, and anneal it to form an organic heterojunction compensation layer, which together with the passivation layer and the conventional bandgap perovskite main absorber layer constitutes an intermediate sub-cell. Step 5: Fabricate an interconnect layer above the intermediate sub-cell; Step 6: Prepare a wide-bandgap perovskite precursor solution, spin-coat it onto the upper surface of the upper interconnect layer, and anneal it to form a wide-bandgap perovskite top cell, thereby obtaining the current-matched enhanced silicon-calcium-calcium triple junction photovoltaic device as described in claim 4.

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