A method for improving energy conversion efficiency and stability of an organic-inorganic hybrid perovskite solar cell

Abstract

The application aims at improving the energy conversion efficiency and stability of organic-inorganic hybrid perovskite solar cells, and particularly relates to a method for reducing the defect state density of an organic-inorganic hybrid perovskite thin film and reducing the maximum value of a valence band (VBM) of a perovskite material to reduce voltage loss and improve the energy conversion efficiency by using a triose small molecule (1,3-dihydroxyacetone, DHA) as a surface passivation agent and through the interaction between DHA and perovskite components. In the process of preparing the perovskite solar cell, a layer of DHA is uniformly deposited on the surface of the perovskite thin film by using a spin coating technique, and is attached to the surface of the perovskite thin film through hydrogen bonding and coordination bonding, thereby playing a role of a protective layer. The application reduces the defects of the perovskite thin film and improves the stability of the thin film and the corresponding device by introducing the DHA passivation layer into the perovskite solar cell; and the material used has low cost and simple processing technology.

Description

TECHNICAL FIELD

[0001] The present application aims to improve the energy conversion efficiency and stability of organic-inorganic hybrid perovskite solar cells. Specifically, it relates to a method for reducing the defect state density of organic-inorganic hybrid perovskite thin film and reducing the valence band maximum (VBM) of perovskite material by using a triose small molecule (1,3-dihydroxyacetone, DHA) as a surface passivation agent, thereby reducing voltage loss and improving energy conversion efficiency. BACKGROUND

[0002] Perovskite solar cells are a new generation of solar cells developed based on dye-sensitized solar cells. Perovskite was first introduced into photovoltaic cells as a visible light sensitizer by Miyasaka in 2008, and an energy conversion efficiency of 3.81% was achieved. Perovskite light absorbing materials have many advantages and have received widespread attention, so the development of perovskite solar cells has been very rapid. After more than ten years of development, the photoelectric conversion efficiency of single-junction solid-state perovskite solar cells has reached 25.7%. However, for the preparation of perovskite light absorbing layer, the mainstream anti-solvent method is difficult to control the crystallization and growth process of perovskite thin film due to the rapid evaporation of solvent and reaction, resulting in many defects, including intrinsic defects of perovskite and defects caused by external factors. These defects will become recombination centers for carriers and cause loss of device performance, and some of these defects will also cause degradation of perovskite, which will adversely affect the stability of perovskite solar cells.

[0003] Since the first introduction of fullerene as a passivation agent into perovskite cells in 2014 to eliminate defects, methods such as additive engineering, solvent engineering, composition engineering, interface engineering, and size engineering have been developed to passivate defects. Surface passivation not only passivates defects, but also has the advantage of serving as a protective layer for perovskite, and the process is simple and widely used. For example, Li's group used PBABr to passivate the surface defects of perovskite thin film, significantly reducing Pb and I defects, and significantly suppressing non-radiative recombination on the surface. You's group deposited a layer of PEAI salt on the surface of perovskite, which reduced the I defects on the surface, and these PEAI crystals can penetrate into the perovskite grain boundaries and suppress non-radiative recombination defects, further improving device performance. Meng's group used triphenylphosphine oxide (TBPO) to achieve sufficient surface passivation by constructing intermolecular-P=O···Pb and π-π conjugation, and stabilized the molecular arrangement on the surface of perovskite. Based on previous reports, we selected a triose molecule as a surface passivation agent, which significantly reduced the defect density of perovskite thin film, reduced voltage loss, improved the absorbance of the thin film, and suppressed the recombination of carriers at the interface. SUMMARY

[0004] Based on this, the purpose of the present application is to use a surface passivation agent to improve the energy conversion efficiency and stability of organic-inorganic hybrid perovskite solar cells.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is:

[0006] An organic-inorganic hybrid perovskite solar cell containing a surface passivation agent, the structure of which is a conductive glass substrate, an electron transport layer, a perovskite layer, a surface passivation layer, a hole transport layer and a metal electrode.

[0007] In the next step of preparing the organic-inorganic hybrid perovskite thin film, an isopropanol solution containing the surface passivation agent is spin-coated on the perovskite thin film, without the need for additional annealing treatment.

[0008] Among them, the surface passivation agent used is 1,3-dihydroxyacetone, the scientific name is 1,3-Dihydroxyacetone, and the abbreviation is DHA.

[0009] Preferably

[0010] DHA is configured into solutions with different concentrations, fully stirred until completely dissolved, and DHA solutions are deposited on the surface of the perovskite thin film using different spin-coating speeds and times. The control group only uses isopropanol solution to spin-coat the perovskite thin film, and then the thin films of some experimental groups are subjected to heat treatment annealing.

[0011] The optimal concentration of the surface passivation agent in the isopropanol solution is 0.4 mg / mL.

[0012] The speed and time of the surface passivation agent in the spin-coating step are 3000 rpm and 20 s.

[0013] The optimal post-treatment of the surface passivation layer thin film is without additional annealing.

[0014] The organic-inorganic hybrid perovskite structure of the organic-inorganic hybrid perovskite thin film is ABX3, A is CH3NH3 (MA) methylamine cation, NH2-CH=NH2 (FA) formamidinium cation and Cs metal ion; B is Pb metal ion; X is I / Br ion.

[0015] The present application has the following advantages:

[0016] By introducing DHA small molecules into the surface of the perovskite thin film, the present application reduces the defect state density of the perovskite thin film, suppresses the recombination of carriers at the interface, reduces the voltage loss, improves the photoelectric conversion efficiency of the device, and can reduce the water contact angle of the perovskite thin film, which is beneficial to the long-term stability of the device.

[0017] The surface passivation agent used has low cost, wide source, easy to operate, good repeatability, and can realize large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The SEM photos of perovskite thin film before and after treatment by the DHA surface passivation agent provided in the examples of the present application; wherein (a) is the control group before DHA treatment, and (b) is the experimental group after DHA treatment.

[0019] Figure 2 The water drop contact angle of perovskite thin film before and after treatment by the DHA surface passivation agent provided in the examples of the present application; (a) is the control group before DHA treatment, and (b) is the experimental group after DHA treatment.

[0020] Figure 3 The XRD patterns of perovskite thin film before and after treatment by the DHA surface passivation agent provided in the examples of the present application.

[0021] Figure 4 The SCLC curves of perovskite devices (ITO / PEDOT:PSS / Perovskite / Sprio-OMeTAD / Au) before and after treatment by the DHA surface passivation agent provided in the examples of the present application, wherein (a) is the control group, and (b) is the experimental group.

[0022] Figure 5 The PL patterns of perovskite thin film before and after treatment by the DHA surface passivation agent provided in the examples of the present application.

[0023] Figure 6 The TRPL patterns of perovskite thin film before and after treatment by the DHA surface passivation agent provided in the examples of the present application.

[0024] Figure 7 The Mott-Schottky curves of perovskite devices before and after treatment by the DHA surface passivation agent provided in the examples of the present application.

[0025] Figure 8 The UV-vis spectra of perovskite thin film before and after treatment by the DHA surface passivation agent provided in the examples of the present application.

[0026] Figure 9 The stability curves of unsealed perovskite devices before and after treatment by the DHA surface passivation agent provided in the examples of the present application.

[0027] Figure 10 The I-V curves of perovskite devices before and after treatment by the DHA surface passivation agent provided in the examples of the present application. DETAILED DESCRIPTION

[0028] 1. Device fabrication

[0029] The etched FTO (fluorine-doped tin oxide) glass substrate with dimensions of (2.26cm × 1.86cm) was sequentially cleaned in alkaline glass cleaning solution, deionized water, acetone, and isopropanol. The substrate was then subjected to plasma treatment for 5 minutes before use.

[0030] The TiO2 electron transport layer was prepared by depositing a 10 nm thick dense TiO2 layer on an FTO substrate using atomic layer deposition (ALD) and sintering it in air at 500°C for 30 min. The SnO2 electron transport layer was prepared by diluting a commercially available SnO2 hydrocolloid dispersant (15%) to 2.67% wt with deionized water. 3 mg of KCl was dissolved in 1 mL of the prepared SnO2 hydrocolloid dispersant and stirred for 10 minutes. The final solution was spin-coated onto the TiO2 film at 3000 rpm for 30 s and annealed in air at 150°C for 30 min to obtain the TiO2 / SnO2 electron transport layer.

[0031] Weigh 24.6 mg CsI, 190.9 mg FAI, 6.4 mg MAI, 591.2 mg PbI2, 39.6 mg PbBr2, and 13.5 mg FABr into 1 mL of a mixed solvent of DMF and DMSO (DMSO:DMF = 4:1). Separately weigh 31.9 mg of MACl (37 mol%) into the above solution. Stir in a glove box for 4 hours to prepare FA0.9Cs. 0.07 MA 0.03 Pb(I 0.9 Br 0.08 3. Precursor Solution. The perovskite thin film was fabricated using a one-step method. The perovskite precursor solution was dropped onto the substrate and spin-coated in two steps: 1000 rpm for 10 seconds and 4000 rpm for 30 seconds. Ten seconds before the end of the second spin-coating step, chlorobenzene (CB) was sprayed onto the perovskite precursor as an anti-solvent, and the film was annealed at 120°C for 40 minutes in air with 20% RH to fabricate the perovskite thin film. For passivated devices, a DHA solution (0.4 mg DHA in 1 mL isopropanol) was spin-coated onto the perovskite thin film at 3000 rpm for 20 seconds without additional annealing. The reference device only required spin-coating of the perovskite thin film with an isopropanol solution.

[0032] Compared to the passivated and reference films, DHA was observed to adhere to the film surface (e.g., Figure 1 ),Depend on Figure 2 The presence of DHA was observed to significantly increase the contact angle of water droplets on the film.

[0033] exist Figure 3The decrease of the PbI2peak at 12.7° in the XRD pattern due to the passivation of DHA can be observed, indicating the interaction between DHA and the residual PbI2on the surface of the perovskite film.

[0034] Referring to Figure 5 and Figure 6 The PL and TRPL tests of the passivated and reference perovskite films show that the passivation reduces the defect states of the perovskite film and suppresses the non-radiative recombination of the film.

[0035] Referring to Figure 8 The coverage of the DHA passivation layer on the surface of the perovskite film does not reduce the light absorption of the film, but rather increases the absorbance in the wavelength range of 500-750 nm.

[0036] The hole transport layer is prepared by spin coating a Sprio-OMeTAD solution on the perovskite film at a speed of 4000 rpm for 20 s, and the Sprio-OMeTAD solution contains 72.3 mg of Sprio-OMeTAD, 17.5 μL of Li-TFSI solution (520 mg of Li-TFSI dissolved in 1 mL of acetonitrile), 28.8 μL of 4-TBP, and 1 mL of chlorobenzene; the Sprio-OMeTAD is oxidized and 40 nm of Au is deposited on the top of the device as an electrode.

[0037] Referring to Figure 4 Another device is prepared for SCLC test, and the device structure is ITO / PEDOT:PSS / Perovskite / Sprio-OMeTAD / Au. It is measured that the passivated device has a lower limiting fill voltage, indicating that the film of the experimental group has a lower defect state density.

[0038] The Mott-Schottky curve of the solar cell obtained in the embodiment is tested by using an electrochemical workstation (as shown in Figure 7 ), and the results show that the device of the experimental group has a higher built-in voltage.

[0039] The I-V performance of the solar cell obtained in the embodiment is measured under a standard sunlight, and the solar cell is placed in an air environment with a humidity of 20% for a long time, referring to Figure 9 and Figure 10 The stability and energy conversion efficiency of the passivated device are significantly improved.

Claims

1. An organic-inorganic hybrid perovskite solar cell containing a triose molecule, the structure of which is a conductive glass substrate, an electron transport layer, a perovskite layer, a surface passivation layer, a hole transport layer, and a metal electrode; characterized in that, The passivation layer is formed by attaching triose molecules as surface passivation agents on the surface of the perovskite thin film, reducing the defect density of the perovskite thin film and protecting the perovskite thin film, thereby improving the energy conversion efficiency and stability of the perovskite solar cell device; the triose molecules as the surface passivation agent are 1,3-dihydroxyacetone (1,3-Dihydroxyacetone), abbreviated as DHA.

2. The organic-inorganic hybrid perovskite solar cell containing a triose molecule according to claim 1, characterized in that, The passivation layer formed by DHA reduces the defect state density of the organic-inorganic hybrid perovskite thin film and reduces the voltage loss of the device.

3. The organic-inorganic hybrid perovskite solar cell containing a triose molecule according to claim 1, characterized in that, The perovskite thin film has a structure formula of ABX3, wherein A is a methylamine cation, a formamidinium cation and a Cs metal ion; B is a Pb metal ion; and X is an I, Br ion.

4. A method for preparing an organic-inorganic hybrid perovskite solar cell, characterized by, The preparation method of the organic-inorganic hybrid perovskite solar cell containing triose molecules in claim 1 or 2 comprises: dissolving the surface passivation agent DHA with a solvent isopropyl alcohol, and the DHA concentration is 0.4 mg / mL. 5.The method of claim 4, wherein the method further comprises, after the step of forming the perovskite layer, a step of forming a back electrode layer on the perovskite layer. After the preparation of the organic-inorganic hybrid perovskite thin film, the solution containing the surface passivation agent DHA is deposited on the perovskite thin film by a spin coating technique, and a passivation layer is formed on the surface thereof by intermolecular forces. 6.The method of claim 4, wherein the method further comprises, after the step of forming the perovskite layer, a step of forming a back electrode layer on the perovskite layer. The passivation layer does not need further heat treatment. 7.The method of claim 4, wherein the method further comprises a step of applying a protective layer on the surface of the perovskite solar cell. The passivation layer has a certain hydrophobicity.

8. Use of a DHA passivation layer in a perovskite solar cell, characterized in that, The DHA passivation layer is attached to the surface of the perovskite thin film.

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