A method for improving the performance of a perovskite cell by grain boundary passivation

Abstract

The application belongs to the method for improving the energy conversion efficiency and stability of organic-inorganic hybrid perovskite solar cells, and the main content is that ethyl benzene sulfonyl lactam (PSAD) containing sulfonamide functional group is combined with-NH2 and Pb 2+ in perovskite material respectively through hydrogen bond and coordination effect to passivate the crystal defects caused by the two kinds of functional groups and cations in perovskite crystal grains. The oxygen atom of the sulfoxide group in PSAD can not only fix the organic amine ion in perovskite through hydrogen bond, but also can form Pb 2+ …O coordination bond with Pb to passivate the defects caused by Pb. The method passivates the grain boundary, reduces the non-radiation recombination of carriers, enhances the charge transport of perovskite thin film, and significantly improves the energy conversion efficiency and stability of perovskite solar cells. The additive PSAD is cheap and easy to obtain, which provides the possibility for industrialization.

Description

TECHNICAL FIELD

[0001] The present application belongs to the method of improving the energy conversion efficiency and stability of lead-based perovskite solar cells, and the main content is that ethyl benzene sulfonyl lactam (PSAD) containing sulfonamide functional group is combined with -NH2 and Pb 2+ respectively through hydrogen bond and coordination, and then passivates the defects of perovskite grain boundary, reduces the non-radiative recombination of carriers, effectively enhances the charge transport of perovskite thin film, and significantly improves the energy conversion efficiency and stability of perovskite solar cells. BACKGROUND

[0002] The energy conversion efficiency of perovskite solar cells has broken through 25% in just a decade, and is gradually approaching its theoretical maximum value, and has great development prospects. Perovskite materials have caused a research boom due to their high absorption coefficient and excellent carrier transport characteristics. However, there are still key problems to be solved such as device stability and large-area preparation in order to achieve industrialization. Studies have shown that during the formation of perovskite thin film, it is inevitable to produce adverse defects in the crystal, grain boundary and surface, which will lead to non-radiative recombination, accelerate the corrosion of water and oxygen, and cause serious reduction of current voltage and other parameters, thereby reducing the efficiency and long-term stability of the device. Therefore, the introduction of some effective chemicals to passivate these defects will greatly help the efficiency and stability of the device. In this regard, we introduce benzene sulfonyl lactam substances into the perovskite precursor solution to passivate the defects of perovskite grain boundary to improve the efficiency and stability of the device: ethyl benzene sulfonyl lactam is dissolved into the perovskite precursor solution to effectively passivate the defects of perovskite grain boundary through hydrogen bond and atomic coordination, and improve the performance and long-term stability of the device. SUMMARY

[0003] The purpose of the present application is to improve the energy conversion efficiency and stability of perovskite solar cells by passivating the grain boundary.

[0004] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0005] First, the additive used is dissolved in a certain volume ratio of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), and then diluted to the best concentration according to a certain proportion before being added to the perovskite precursor solution. After spin coating and annealing, the perovskite thin film doped with the additive can be obtained.

[0006] Among them, the sulfonamide additive is named 3-ethyl-benzoisothiazole-1,1-dioxide, and is abbreviated as PSAD.

[0007] Preferably

[0008] The required components are mixed in proportion, dissolved in DMSO / DMF as a solvent, and fully stirred until completely dissolved to obtain a precursor solution. A lead-based perovskite film is prepared by an anti-solvent method, the anti-solvent is chlorobenzene, the precursor solution of the control group does not contain an additive, and the precursor solution of the experimental group is added with the dilute additive in advance.

[0009] The optimal mass concentration of the additive in the precursor solution is 0.5 mg / mL.

[0010] The heat treatment temperature of the thin film is 100 DEG C.

[0011] The present application has the advantages of:

[0012] The present application introduces a sulfonamide organic small molecule PSAD into the perovskite film, and the oxygen atom in the sulfoxide group can not only fix the organic amine ion in the perovskite through hydrogen bonding, but also form a Pb...O coordination bond to passivate the defects of the grain boundary. 2+ This method reduces the non-radiative recombination of carriers, effectively enhances the charge transport of the perovskite film, and significantly improves the energy conversion efficiency and stability of the perovskite solar cell.

[0013] Meanwhile, the additive material used has a low cost and is easy to operate in the process.

[0014] The process of the present application is easy to operate, has good repeatability, and is suitable for large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 The XRD patterns of the perovskite films prepared before and after introducing PSAD in the precursor solution provided in the embodiments of the present application.

[0016] Figure 2 The SEM photos of the perovskite films prepared before and after introducing PSAD in the precursor solution provided in the embodiments of the present application; wherein a) is before adding PSAD, and b) is after adding 0.4 mg / ml PSAD.

[0017] Figure 3 The NMR patterns of the important component of the precursor, formamidinium iodide (FAI), before and after introducing PSAD provided in the embodiments of the present application.

[0018] Figure 4 The XPS patterns of the perovskite films prepared before and after introducing PSAD in the precursor solution provided in the embodiments of the present application.

[0019] Figure 5 The FTIR patterns of the perovskite cells prepared before and after introducing PSAD in the precursor solution provided in the embodiments of the present application.

[0020] Figure 6I-V curves of perovskite thin films prepared before and after introducing PSAD in the precursor solution provided by the embodiments of the present application.

[0021] Figure 7 Air stability curves of un-encapsulated perovskite cells prepared before and after introducing PSAD in the precursor solution provided by the embodiments of the present application.

[0022] Figure 8 PL curves of perovskite cells prepared before and after introducing PSAD in the precursor solution provided by the embodiments of the present application.

[0023] Figure 9 TRPL curves of perovskite cells prepared before and after introducing PSAD in the precursor solution provided by the embodiments of the present application.

[0024] Figure 10 TPV curves of perovskite cells prepared before and after introducing PSAD in the precursor solution provided by the embodiments of the present application. DETAILED DESCRIPTION

[0025] 1. Device preparation

[0026] (1) Preparation of perovskite precursor solution

[0027] Accurately weigh 228.8 mg of FAI, 18.2 mg of Csl, 33.7 mg of MACl, 705.3 mg of Pbl2, 4.3 mg of MABr, and 13.9 mg of PbBr2, and dissolve them in 1 mL of a mixed solvent of DMF and DMSO (volume ratio of DMF:DMSO = 9:1).

[0028] (2) Pretreatment of substrate

[0029] The etched fluorine-doped tin oxide (FTO) glass substrate is sequentially cleaned with a cleaning agent, deionized water, ethanol, and isopropanol for 15 minutes, then dried with a nitrogen gun, and treated with O2 plasma for 500 seconds for standby.

[0030] (3) Preparation of electron transport layer

[0031] A dense TiO2 layer is deposited on the FTO substrate by atomic layer deposition (ALD), and then sintered at 500°C for 30 minutes in an air environment. The SnO2 colloidal precursor is synthesized by hydrolysis of SnCl4. The SnO2-based electron transport layer is spin-cast on a pre-cleaned FTO glass at a speed of 3000 rpm / s for 30 seconds, and then annealed at 180°C for 30 minutes in an air atmosphere.

[0032] (4) Preparation of perovskite thin film

[0033] The perovskite precursor solution was spin-coated in two steps, first at 1000 rpm for 10 s and then accelerated to 4000 rpm for 30 s, 300 μΐ^of benzyl ether was dropped on the spinning substrate 20 s before the end of the second step. When the modified device was prepared, different concentrations of PSAD solution were pre-dissolved in the perovskite precursor solution. Subsequently, all the perovskite films were annealed at 100 °C in air (relative humidity 20-30%) for 40 min. The main peak (110) face intensity was enhanced and its FWHM was also reduced after PSAD modification, which indicated that the crystallization performance of the crystal was improved after the addition of the additive. The peak of PbI2was weakened after the addition of PSAD, indicating that the defects caused by PbI2could be effectively passivated and the decomposition of the perovskite could be slowed down after the addition of PSAD (see Figure 1 ). It can be seen from the SEM map (see Figure 2 ) that the grain size of the perovskite film increased after the addition of PSAD. And the additive was aggregated at the grain boundary of the perovskite, which improved the quality of the perovskite film.

[0034] (5) Preparation of passivation layer

[0035] 40 μΐ^of PTABr solution with a concentration of 1 mg / mL was deposited on the annealed perovskite film at 4000 rpm and 20 s.

[0036] (6) Preparation of hole transport layer

[0037] 40 μΐ^of spiro-OMeTAD solution in chlorobenzene containing 72.3 mg of spiro-OMeTAD, 28.8 μΐ^of 4-tert-butylpyridine and 17.5 μΐ^of Li-TFSI solution (520 mg of Li-TSFI in 1 mL of acetonitrile) was taken and deposited on the perovskite film at a speed of 4000 rpm for 20 s.

[0038] (7) Preparation of metal electrode

[0039] 80 nm Au electrode was deposited by thermal evaporation under vacuum conditions.

[0040] NMR, XPS and FTIR maps reflect the hydrogen bonding and coordination between the additive PSAD and the perovskite (see Figure 3 , 4 and 5). The perovskite device is placed in the air and heated environment for a long time, which can accelerate the damage of the film, and the stability characterization can show the speed and degree of film damage. I-V performance measurement (see Figure 6 ) was carried out, which was measured between -0.1 V and 1.2 V in forward and reverse scanning, and it can be seen that the energy conversion efficiency of the device containing PSAD is obviously improved. The air stability curve (see Figure 7) is the change of normalized PCE value of unencapsulated perovskite device in the dark at room temperature and relative humidity of 20±5%, the PCE of control device reduces to 30% at 1000 hours, while the PCE of PSAD-modified device still remains 80% of the initial PCE at 1300 hours, indicating that the additive PSAD can effectively improve the stability of perovskite solar cells. From the PL curves (see Figure 8 ) we can see that the luminescence intensity of PSAD-modified perovskite film is much higher than that of the original perovskite film, indicating that the internal defect state of PSAD-modified perovskite film is reduced, the carrier lifetime is increased, and non-radiative recombination can be effectively suppressed. Similarly, through the TRPL curves (see Figure 9 ) we can see that the carrier lifetime of PSAD-modified perovskite film is significantly increased, which means that the trap-assisted recombination and the non-radiative recombination inside the particles are effectively suppressed, the trap state is reduced, and the carrier transport of perovskite film is enhanced. By measuring the transient photo-voltage (TPV, see Figure 10 ) to further understand the carrier lifetime and recombination kinetics of doped PSAD and undoped PSAD devices. From the figure we can see that the decay time of PSAD-doped device is significantly longer than that of the control device, the extension of decay time indicates that the carrier lifetime of PSAD-modified device is increased, the defect density is reduced, and the non-radiative recombination is suppressed. And this can lead to the increase of open-circuit voltage (Voc) and fill factor (FF), which is consistent with the previous characterization of PL and TRPL results.

Claims

1. A method for improving the energy conversion efficiency and stability of lead-based perovskite solar cell devices using small organic molecules containing sulfonamide functional groups, characterized in that, An additive containing a sulfonamide functional group of an organic small molecule is added to a lead-based perovskite precursor solution, and a perovskite film doped with the additive is obtained by spin coating; the additive is chemically named 3-ethyl-benzoisothiazole-1,1-dioxide, abbreviated as PSAD.

2. The method for improving the energy conversion efficiency and stability of lead-based perovskite solar cell devices using organic small molecules containing sulfonamide functional groups according to claim 1, characterized in that, Passivation of grain boundaries reduces nonradiative recombination of charge carriers, enhances charge carrier transport in perovskite thin films, and significantly improves the energy conversion efficiency and stability of perovskite solar cells.

3. The method for improving the energy conversion efficiency and stability of lead-based perovskite solar cell devices using organic small molecules containing sulfonamide functional groups according to claim 1 or 2, characterized in that, The additive is a sulfonamide derivative.

4. The method for improving the energy conversion efficiency and stability of lead-based perovskite solar cell devices using organic small molecules containing sulfonamide functional groups according to claim 1 or 2, characterized in that, The optimal concentration of the additive in the precursor solution is 0.5 mg / ml.

5. The method for improving the energy conversion efficiency and stability of lead-based perovskite solar cell devices using organic small molecules containing sulfonamide functional groups according to claim 1 or 2, characterized in that, The additives used are first dissolved in N,N-dimethylformamide and dimethyl sulfoxide in a certain volume ratio, and then diluted to the optimal concentration in a certain proportion before being added to the perovskite precursor solution. After spin coating and annealing, the perovskite film doped with the additives can be obtained.

6. The method for improving the energy conversion efficiency and stability of lead-based perovskite solar cell devices using organic small molecules containing sulfonamide functional groups according to claim 2, characterized in that, The annealing temperature for perovskite films is 100℃.

7. The method for improving the energy conversion efficiency and stability of lead-based perovskite solar cell devices using organic small molecules containing sulfonamide functional groups according to claim 1 or 2, characterized in that, The organic-inorganic perovskite structure of the prepared perovskite film is ABX3, where A is a cation containing methylamine ion, formamidinium ion and cesium ion; B is Pb ion; and X is I, Br and Cl ion.

8. An improved perovskite solar cell prepared by the method described in claim 4 or 5, which utilizes organic small molecules containing sulfonamide functional groups to improve the energy conversion efficiency and stability of lead-based perovskite solar cell devices, characterized in that... Compared to the reference device, perovskite solar cells with additives have higher energy conversion efficiency and stability.

Images