Preparation Method of a Wide-Spectrum Absorbing Mesoporous Quantum Dot Parallel Stacked Solar Cell

Abstract

The present invention discloses a preparation method of a wide-spectrum absorption mesoporous quantum dot parallel stacked solar cell. The method includes: using large-particle mesoporous titanium dioxide as an electron transport layer on a conductive glass, and using it as a scaffold for synthesizing a variety of quantum dot light-absorbing layers through thermal injection; depositing a hole transport layer on the light-absorbing layer material; and evaporating a metal electrode on the hole transport layer. A variety of nanoscale materials relying on mesoporous materials can expand the long-wave response range of the solar cell, and the direct contact between the quantum dot material and the mesoporous scaffold can achieve efficient extraction and multi-channel transport of carriers; the pre-synthesized quantum dot material can overcome the complex crystallization kinetics of perovskite during the spin-coating process, improve the film-forming quality, and meet the requirements for preparing high-efficiency perovskite solar cells in the photovoltaic field.

Description

Technical Field

[0001] The present invention belongs to the field of photovoltaic technology, and particularly relates to a preparation method for a novel structure of a tandem solar cell. Background Art

[0002] Since the efficiency of perovskite single-junction solar cells reached 3.8% in 2009, the efficiency of single-junction perovskite solar cells has increased to the current 25.5% in just over a decade, approaching the limiting efficiency of single-junction solar cells. To break through the single-junction Shocley-Queisser limit, using light-absorbing materials with different bandgaps to form a tandem cell structure is the only way to make full use of the spectrum and improve the photoelectric conversion efficiency of solar cells.

[0003] Currently, forming a tandem cell structure with light-absorbing materials having different bandgaps includes a series cell structure and a parallel cell structure. Compared with series tandem solar cells, parallel tandem cells have the following advantages: (1) avoiding the photoelectric loss of tunneling junctions and not requiring strict current matching; (2) a cascading energy level design enables carriers to be continuously accelerated to obtain high kinetic energy, realizing the effective utilization of high-energy photons and reducing the recombination probability; (3) it is expected to obtain a multi-carrier excitation effect and an impurity photovoltaic effect, enabling the short-circuit current to exceed the sum of the currents of each sub-cell and achieving a further breakthrough in efficiency. Quantum dot materials can have their bandgaps continuously adjusted by controlling the quantum dot size, composition, and surface ligand type, and have natural advantages in the application of tandem cells, which can minimize the built-in electric field loss caused by lattice mismatch. Thanks to the development of nano-materials such as quantum dots in recent years, it has made it possible to construct parallel structure solar cells, and successful prototype devices include organic hybrid multi-phase heterostructures, multi-bandgap quantum dot-sensitized solar cell structures, etc. Therefore, using a parallel tandem structure with quantum dot materials having different bandgaps and using mesoporous TiO 2 Improving the carrier transport ability, performing energy band matching, and improving the cell efficiency are urgent problems to be solved in the research and development process of tandem solar cells. Summary of the Invention

[0004] Object of the present invention: Aiming at the above problems, we propose to use quantum dot materials with different bandgaps to achieve wide-spectrum superposition absorption, and solve the problems of large carrier thermalization loss and low open-circuit voltage of a single narrow-bandgap material. Combining the advantages of adjustable bandgap and excellent optoelectronic properties of perovskite quantum dots with a mesoporous electron transport layer, a novel parallel tandem solar cell prototype device with wide-spectrum multi-bandgap absorption, multi-channel carrier transport, and wide-spectrum efficient utilization is constructed.

[0005] Technical solution of the present invention: The present invention provides a preparation method for a wide-spectrum absorption mesoporous quantum dot parallel tandem solar cell and a wide-spectrum absorption mesoporous parallel tandem solar cell to improve the utilization rate of sunlight and thus improve the efficiency of solar cells.

[0006] The present invention provides a method for preparing a wide-spectrum absorption mesoporous quantum dot parallel stacked solar cell, and the method includes: (1) preparing a planar dense and mesoporous TiO 2 electron transport layer on fluorine-doped tin oxide (FTO) conductive glass; (2) sequentially depositing quantum dot light-absorbing layer materials on the electron transport layer; (3) depositing a P-type hole transport layer on the light-absorbing layer; (4) evaporating a metal electrode layer on the P-type hole transport layer. The quantum dot light-absorbing layer materials include 10-nm CsPbBr 3 quantum dots, 10-nm CsPbI 3 quantum dots, 4-nm PbS quantum dots, and 7-nm PbS quantum dots, and all the quantum dot materials are dispersed layer by layer in mesoporous TiO 2 . The 7-nm PbS quantum dots are located in the upper layer of mesoporous TiO 2 to prevent direct connection between the electron transport layer and the hole transport layer, which may cause leakage.

[0007] Working principle of the present invention:

[0008] First, quantum dot materials are sequentially deposited in the mesoporous titanium dioxide electron transport layer as light-absorbing layer materials to achieve efficient extraction and multi-channel transport of carriers. The utilization rate of sunlight by quantum dot materials with different bandgaps is greatly improved, and finally, the performance of the parallel stacked solar cell device is optimized. Among them, the bandgap of CsPbBr 3 quantum dots is 2.3 eV, the bandgap of CsPbI 3 quantum dots is 1.7 eV, the bandgap of 4-nm PbS is 1.35 eV, and the bandgap of 7-nm PbS is 0.90 eV. Sequentially depositing each quantum dot material can achieve multi-bandgap light absorption, multi-channel carrier transport, and wide-spectrum efficient utilization, avoiding the problem of large carrier thermalization loss in a single narrow-bandgap material. While the finally constructed parallel stacked wide-spectrum quantum dot battery obtains an ultra-high short-circuit current, it maintains a relatively high open-circuit voltage of the blend system. On the other hand, the present invention can absorb and utilize photon energy as low as 0.90 eV, and the long-wave response is expected to be extended to 1300 nm. Theoretically, it can absorb and utilize ~90% of the total radiation of the AM1.5G solar spectrum. Second, the preparation process of the present invention is compatible with existing low-cost thin-film solar cells, and is expected to become a new research hotspot for high-efficiency and low-cost solar cell technologies.

[0009] Beneficial effects of the present invention:

[0010] Quantum dot absorption layer materials with different bandgaps greatly improve the utilization rate of sunlight, and the long-wave response range is expected to be extended to 1300 nm. Combined with mesoporous TiO 2The support structure of the electron transport layer forms a multi-channel electron transport path, improving the carrier transport efficiency and enhancing the device performance of the tandem stacked cell. Description of the Drawings

[0011] Figure 1 is a schematic diagram of the structure of the fabricated tandem stacked device

[0012] Figure 2 is mesoporous TiO 2 scanning electron microscope (SEM) image

[0013] Figure 3 is the photoluminescence (PL) image of the fabricated quantum dot film

[0014] Figure 4 is the X-ray diffraction (XRD) pattern of the fabricated CsPbBr 3 and PbS quantum dot films

[0015] Figure 5 is the transmission electron microscope (TEM) image of the fabricated CsPbBr 3 quantum dots Detailed Description of the Invention

[0016] As Figure 1 shown, it is a schematic diagram of the cell structure obtained by the preparation method of the broadband absorption mesoporous quantum dot tandem stacked solar cell in the specific embodiment of the present invention. The solar cell includes:

[0017] (1) Planar dense and mesoporous TiO 2 electron transport layer ETL;

[0018] (2) Quantum dot materials with different bandgaps as the light absorption layer, sequentially deposited in the mesoporous TiO 2 electron transport layer;

[0019] (4) Hole transport layer material HTL, spin-coated on the quantum dot material;

[0020] (5) Metal electrodes are respectively evaporated on the FTO conductive glass layer and the hole transport layer.

[0021] The specific preparation and preparation process of a broadband absorption mesoporous quantum dot tandem stacked solar cell device are as follows:

[0022] The FTO conductive glass is ultrasonically cleaned successively with deionized water, ethanol, and acetone, and each step requires 15 minutes. After taking out the ultrasonically cleaned substrate, it is dried with a hair dryer for standby; A dense TiO 2 precursor solution is obtained by appropriately mixing hydrochloric acid, titanium isopropoxide, and isopropanol; And ethyl cellulose is used as a pore-forming agent and TiO synthesized by the hydrothermal method 2Preparation of mesoporous TiO by mixing nanoparticles 2 slurry

[0023] TiO 2 Preparation of electron transport layer:

[0024] (1) First deposit a planar dense TiO 2 electron transport layer on FTO conductive glass at a rotation speed of 4000 rpm, and anneal it at 500 °C in a tube furnace for 30 min;

[0025] (2) Prepare a mesoporous TiO 2 electron transport layer on the planar dense TiO 2 electron transport layer by spin coating method, and use stepwise annealing at 500 °C for 30 min during the high-temperature annealing process. Figure 2 is the scanning electron microscope image of mesoporous TiO 2

[0026] Preparation of precursor solution of quantum dot light-absorbing layer material:

[0027] CsPbBr 3 Quantum dots: Using a double-tube device, dissolve 0.814 g of Cs 2 CO 3 in 40 ml of octadecene and 2.5 ml of oleic acid, degas at 120 °C for 1 h, and then introduce N 2 to react for half an hour to prepare the cesium source; dissolve 0.069 g of PbBr 2 in 5 ml of octadecene, degas under vacuum at 120 °C for 1 h, and then introduce N 2 and add 0.5 ml of oleylamine and oleic acid respectively to promote the dissolution of lead bromide; raise the temperature to 180 °C for rapid thermal injection, and quickly place the reaction solution in ice water to terminate the reaction after 5 s. CsPbI 3 Quantum dots and PbS quantum dots are prepared by the same thermal injection method. Figure 5 is the transmission electron microscope image of CsPbBr 3 quantum dots synthesized by thermal injection.

[0028] Preparation of quantum dot thin film:

[0029] All quantum dot materials are prepared by spin coating method, rotating at low speed of 1000 rpm for 15 s and high speed of 2000 rpm for 5 s. CsPbBr 3 and CsPbI 3 quantum dot thin films are both cleaned with methyl acetate, and PbS quantum dots are cleaned with methanol. Figure 3 is the photoluminescence PL image of the prepared CsPbBr 3 quantum dot thin film. Figure 4 is the tested CsPbBr​3 XRD patterns of quantum dot films and PbS films.

[0030] Preparation of hole transport layer:

[0031] 72.3 mg of spiro-OMeTAD was dissolved in 1 ml of chlorobenzene, and 18 μl of lithium salt solution and 28 μl of 4-TBP solution were added to chlorobenzene for P-type doping. After sufficient stirring, a hole transport layer film was prepared by spin coating.

[0032] The gold electrode is evaporated under high vacuum with a thickness of 70nm. The battery is now ready.

Claims

1. Preparation method of a wide-spectrum absorption mesoporous quantum dot parallel stacked solar cell, Characterized in that, The method includes: (1) Prepare planar dense and mesoporous TiO on FTO conductive glass 2 as the electron transport layer; the preparation method of the electron transport layer includes: firstly deposit planar dense TiO on FTO conductive glass by spin coating 2 , with a rotation speed of 4000 rpm, a time of 40 s, a pre-annealing temperature of 100 °C, a time of 10 min, and then anneal at 500 °C for 30 min; then prepare mesoporous TiO on the planar dense TiO2 by doctor blade coating 2 , with a pre-annealing temperature of 100 °C, a time of 10 min, and then stepwise anneal at 500 °C for 30 min; (2) Deposit a light-absorbing layer on the electron transport layer; the preparation method of the light-absorbing layer includes: depositing 10 nm of CsPbBr 3 quantum dots, and then depositing CsPbI with a particle diameter of 10 nm thereon 3 quantum dots, and continuing to deposit PbS quantum dots with a particle diameter of 4 nm on the CsPbI 3 quantum dots. These three types of quantum dots are sequentially embedded in mesoporous TiO 2 , and finally, a PbS quantum dot layer with a particle diameter of 7 nm is placed above the mesoporous TiO 2 structure; (3) Depositing a P-type hole transport layer on the light absorption layer; (4) Evaporating a metal electrode layer on the P-type hole transport layer.

2. The preparation method of the wide-spectrum absorption mesoporous quantum dot parallel stacked solar cell according to claim 1, Characterized in that: The quantum dot materials CsPbBr 3 , CsPbI 3 and PbS are all prepared by the hot injection method; the hot injection method is as follows: for CsPbBr 3 quantum dots, a double-tube device is used. Dissolve 0.814 g of Cs 2 CO 3 in 40 ml of octadecene and 2.5 ml of oleic acid, degas at 120 °C for 1 h, and then introduce N 2 to react for half an hour to prepare the cesium source; dissolve 0.069 g of PbBr 2 in 5 ml of octadecene, degas under vacuum at 120 °C for 1 h, and then introduce N 2 and add 0.5 ml of oleylamine and oleic acid respectively to promote the dissolution of lead bromide; raise the temperature to 180 °C for rapid hot injection, and quickly place the reaction solution in ice water to terminate the reaction after 5 s; CsPbI 3 quantum dots and PbS quantum dots are prepared by the same hot injection method.

3. The preparation method of the wide-spectrum absorption mesoporous quantum dot parallel stacked solar cell according to claim 1, Characterized in that, Quantum dot materials at a certain concentration are embedded in mesoporous TiO by spin coating 2 Among them, 10-nm CsPbBr 3 quantum dots, 10-nm CsPbI 3 quantum dots, and 4-nm PbS quantum dots can all be in direct contact with mesoporous TiO 2 directly.

4. The preparation method of the wide-spectrum absorption mesoporous quantum dot parallel stacked solar cell according to claim 1, Characterized in that, The mesoporous TiO 2 has a thickness of 550 nm - 650 nm, and the 10 nm CsPbBr 3 quantum dots have a thickness of 130 - 150 nm, and the 10 nm CsPbI 3 quantum dots have a thickness of 130 - 150 nm, the PbS quantum dots with a particle size of 4 nm have a thickness of 270 - 300 nm, and the PbS quantum dot layer with a particle size of 7 nm has a thickness of 100 - 150 nm.

5. The preparation method of the wide-spectrum absorption mesoporous quantum dot parallel stacked solar cell according to claim 1, Characterized in that, The preparation method of the P-type hole transport layer material includes the following steps: Dissolve 72.3 mg of spiro-OMeTAD into 1 ml of chlorobenzene, and add 18 μl of lithium salt solution and 28 μl of 4-TBP solution into the chlorobenzene for P-type doping, and stir well.

6. The preparation method of the wide-spectrum absorption mesoporous quantum dot parallel stacked solar cell according to claim 1, Characterized in that, The evaporation of the metal electrode layer on the P-type hole transport layer includes: Depositing a metal electrode under high vacuum conditions; The metal electrode is a gold electrode or a silver electrode; The electrode thickness is 70 nm.

Images