Method for improving performance and stability of perovskite solar cells

Abstract

This invention relates to a method for improving the photoelectric conversion efficiency and stability of perovskite solar cells. This method utilizes a novel ionic liquid (DPPIQ). + PF6 ‑ This also reduces bulk and surface defects in perovskite films. PF6, in particular, [is mentioned here]. ‑ Distributed within the perovskite film, it immobilizes organic amine ions in the perovskite through hydrogen bonds; and the DPIQ within it... + Due to its large size, Pb is passivated on the surface of the perovskite film through anion-π interactions. 2+ Ultimately, the addition of this ionic liquid significantly improved the photoelectric conversion efficiency and stability of perovskite solar cells.

Description

Technical Field

[0001] This invention pertains to a method for improving the photoelectric conversion efficiency and stability of perovskite solar cells. This method utilizes an ionic liquid passivator to reduce bulk and surface defects within the perovskite thin film through hydrogen bonding and anion-π interactions, and effectively suppresses charge recombination in the perovskite, reducing non-radiative recombination in perovskite devices. Background Technology

[0002] Perovskite solar cells have attracted widespread attention due to their high photoelectric conversion efficiency and offer broad prospects for the future development of photovoltaic technology. However, the commercialization of perovskite cells still faces some challenges, such as further improving device efficiency to approach the theoretical limit, and the stability of perovskite devices under the influence of water, heat, light, and oxygen. These issues are mainly caused by defects present inside and on the surface of the perovskite, which can lead to charge recombination and interfacial energy loss, reducing device performance. Simultaneously, the presence of these defects allows water and oxygen to penetrate the perovskite, causing device degradation and decomposition.

[0003] Reducing surface defects in perovskite thin films through chemical doping is an important method in passivation engineering. The Qu group introduced an imidazole tetrafluoroborate ionic liquid into perovskite precursors, increasing grain size, reducing defect density, and improving device storage stability. The Liu group used an imidazole hexafluorophosphate ionic liquid to passivate the perovskite surface, lowering the energy barrier between the perovskite and hole transport layer and significantly suppressing nonradiative recombination. Furthermore, this ionic liquid exhibits some hydrophobicity, effectively enhancing the stability of perovskite devices. Based on the above-reported work, we independently synthesized a novel ionic liquid. This ionic liquid additive can simultaneously reduce bulk and surface defects in perovskite thin films and suppress nonradiative recombination. Summary of the Invention

[0004] The purpose of this invention is to improve the photoelectric conversion efficiency and stability of perovskite solar cells.

[0005] To achieve the above objectives, the present invention employs the following method:

[0006] The synthesized ionic liquid additive was first dissolved in N,N-dimethylformamide (DMF) and then added to a precursor solution dissolved in dimethyl sulfoxide (DMSO). After complete dissolution, it was used to prepare high-quality perovskite thin films.

[0007] The ionic liquid additive used is scientifically named 9-bromo-6,7-diphenylpyrido[2,1-a]isoquinolin-5-ium hexafluorophosphate, abbreviated as DPIQ. +PF6 - .

[0008] Preferred

[0009] The perovskite precursor solution is prepared by adding PbI2, FAI, MACl, MABr, and PbBr2 to a mixed solution of DMF and DMSO in a certain proportion. However, the doped perovskite precursor solution requires the additives to be added to DMF in advance and prepared to different concentrations.

[0010] Through multiple experiments, we determined that the optimal concentration of the additive was 0.3 mg / mL.

[0011] Advantages of this invention:

[0012] This method involves introducing (DPPIQ) into perovskite thin films. + PF6 - Ionic liquids can effectively reduce bulk and interface defects in perovskite films, which is beneficial for reducing defect-induced charge recombination losses.

[0013] The perovskite solar cells prepared according to the method of the present invention exhibit higher efficiency and improved device stability.

[0014] Meanwhile, the additives used are low-cost and easy to process. Attached Figure Description

[0015] Figure 1 DPPIQ was introduced into the perovskite precursor solution provided in the embodiments of the present invention. + PF6 - XRD patterns of perovskite thin films prepared before and after processing.

[0016] Figure 2 DPPIQ was introduced into the perovskite precursor solution provided in the embodiments of the present invention. + PF6 - SEM images of the perovskite films prepared before and after treatment; the left image is the reference, and the right image is the film after the addition of 0.3 mg / mL DPPIQ. + PF6 - The following pictures.

[0017] Figure 3 DPPIQ was introduced into the perovskite precursor solution provided in the embodiments of the present invention. + PF6 - IV curves of perovskite solar cells prepared before and after fabrication.

[0018] Figure 4 DPPIQ was introduced into the perovskite precursor solution provided in the embodiments of the present invention. + PF6 -Dark IV curves of the pure electronic device (left) and the pure hole device (right) prepared before and after.

[0019] Figure 5 DPPIQ is introduced into the precursor solution provided in the embodiments of the present invention. + PF6 - Stability curves of the packaged devices of the perovskite solar cells prepared before and after MPP illumination.

[0020] Figure 6 For DPIQ + PF6 - The synthetic route.

[0021] Figure 7 It is an electrochemical synthesis reaction apparatus.

[0022] Figure 8 For DPIQ + PF6 - of 1 H NMR spectrum.

[0023] Figure 9 For DPIQ + PF6 - of 13 C10 NMR spectrum.

[0024] Figure 10 For DPIQ + PF6 - HRMS spectrum. Detailed implementation method:

[0025] 1. Device fabrication

[0026] (1) Preparation of perovskite precursor solution

[0027] Accurately weigh 228.8 mg FAI, 18.2 mg CsI, 33.7 mg MACl, 705.3 mg PbI2, 4.3 mg MABr, and 13.9 mg PbBr2, and dissolve them in a 1 mL mixture of DMF and DMSO (volume ratio DMF:DMSO = 9:1).

[0028] (2) Substrate pretreatment

[0029] The etched fluorine-doped tin oxide (FTO) glass substrate was cleaned sequentially with 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 later use.

[0030] (3) Fabrication of electron transport layer

[0031] A dense TiO2 layer was deposited on an FTO substrate by atomic layer deposition (ALD), followed by sintering at 500°C for 30 minutes in ambient air. The SnO2 colloidal precursor was synthesized via SnCl4 hydrolysis. The SnO2-based electron transport layer was spin-cast onto pre-cleaned FTO glass at 3000 rpm / s for 30 seconds, followed by annealing at 180°C for 30 minutes in air.

[0032] (4) Preparation of perovskite thin films

[0033] The perovskite precursor solution was spin-coated in a two-step process: first, at 1000 rpm for 10 seconds, then accelerated to 5000 rpm for 30 seconds; finally, 600 μL of diethyl ether was dropped onto the spin-coated substrate 20 seconds before the end of the second step. Different concentrations of DPIQ were used to fabricate the doped devices. + PF6 - The solution was pre-dissolved in the perovskite precursor solution. All perovskite films were then annealed in air (20%–30% relative humidity) at 120°C for 40 minutes. Compared to the experimental group films, the reference group films showed enhanced XRD peak intensity, no significant shift in peak position, and no new peaks, indicating that the introduction of the ionic liquid did not lead to the formation of a new perovskite phase (e.g., ...). Figure 1 Simultaneously, SEM surface images (such as...) Figure 2 Display DPPIQ + PF6 - The introduction of this will reduce uncoordinated PbI2 ( Figure 2 The white grains in the film improved the quality of the film.

[0034] (5) Preparation of passivation layer

[0035] 40 μL of 1 mg / mL PTABr was deposited on an annealed perovskite film at 4000 rpm for 20 s.

[0036] (6) Preparation of hole transport layer

[0037] Take 40 μL of a chlorobenzene solution of spiro-OMeTAD containing 72.3 mg spiro-OMeTAD, 28.8 μL 4-tert-butylpyridine and 17.5 μL Li-TFSI solution (520 mg Li-TSFI in 1 mL acetonitrile) and deposit it on a perovskite film at 4000 rpm for 20 seconds.

[0038] (7) Preparation of metal electrodes

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

[0040] When performing IV testing, the measurement conditions are a scan between 0V and 1.2V. We can then observe the presence of DPPIQ. + PF6 - The efficiency of the device has been improved (see...) Figure 3 Then, using the space charge-limited current (SCLC) method, we estimated the added DPPIQ. + PF6 - And without adding DPPIQ + PF6 - Defect density of perovskite thin films. We calculated the electron defect density and hole defect density using a purely electronic device with an ITO / SnO2 / Perovskite / PCBM / Ag configuration and a purely hole device with an ITO / PEDOT:PSS / Perovskite / Spiro-OMeTAD / Au configuration, respectively. Defect density (n t It can be derived from the equation: V TFL =en t L 2 / 2εε0 is obtained, where V TFL The JV curve of the device was obtained from measurements taken in the dark. Figure 4 (e is the elementary charge, L is the thickness of the perovskite film, and ε and ε0 are the relative permittivity and vacuum permittivity of the perovskite, respectively.) Figure 4 As shown, add DPPIQ + PF6 - Afterwards, the electron defect density and hole defect density of the perovskite thin film increased from 2.25 × 10⁻⁶ to 2.25 × 10⁻⁶. 16 cm -3 Reduced to 1.84×10 16 cm -3 and 2.55×10 16 cm -3 Reduced to 1.95×10 16 cm -3 This is due to DPPIQ + PF6 - This is caused by the passivation effect on grain boundaries and thin film surface defects.

[0041] Figure 5 The stability of the device at the maximum power point (MPPT) was demonstrated. The results show that the doped packaged device retains 90% of its initial efficiency after 1260 hours of continuous illumination, while the reference device retains 90% of its initial efficiency after 492 hours of continuous illumination. These results demonstrate that the DPIQ... + PF6 - It can effectively passivate defects, thereby improving the long-term stability of the device.

[0042] 2.DPPIQ + PF6- Synthesis

[0043] See additive synthesis route Figure 6 The reaction apparatus is shown below. Figure 7 .

[0044] The reaction was carried out electrocatalystically in an unseparated electrolytic cell under air, with a graphite felt (GF) anode (10 mm × 10 mm × 5 mm) and a platinum cathode (10 mm × 10 mm × 0.25 mm). In a 10 mL three-necked flask, 2-arylpyridine 1 (0.2 mmol), alkyne 2 (0.22 mmol), [Cp*RhCl2]2 (0.5 mol%), and KPF6 (0.4 mmol, 2.0 equivalent) were dissolved in a HFIP / H2O mixture (3:1, 5 mL). Electrocatalysis was carried out at 35 °C with a constant current of 3.0 mA maintained for 3.5 h. When the reaction was complete, the mixture was diluted with CH2Cl2 (10 mL). The GF anode was washed with CH2Cl2 (3 × 5 mL) in an ultrasonic bath, and all solvent was transferred to a round-bottom flask. The mixture was filtered through a diatomaceous earth mat, which was washed with CH2Cl2 (30 mL). The filtrate was concentrated and purified by silica gel column chromatography using DCM / MeOH (95:5) as the eluent to give a yellow solid in 76% yield.

[0045] DPPIQ + PF6 - NMR and high-resolution mass spectrometry data. Relevant spectra are shown in Figures 8-10.

[0046] 1 H NMR(500MHz, DMSO-d6)δ9.75(d,J=8.6Hz,1H),9.31(d,J=9.0Hz,1H),8.82~8.73(m,2H),8.38~8.31(m,1H) ,8.15(t,J=6.8Hz,1H),7.54(d,J=1.6Hz,1H),7.51~7.45(m,5H),7.41~7.34(m,3H),7.27(d,J=6.8Hz,2H).

[0047] 13 C NMR (125MHz, DMSO-d6) δ143.46,140.98,140.00,137.64,134.60,134.18,133.91,131.38,131. 27,130.68,130.34,129.83,129.11,129.04,128.97,128.76,128.69,125.58,124.17,124.04.

[0048] HRMS(ESI)calculated for[C 25 H 17 BrN + ](M-PF6) + :410.0534,found 410.05。

Claims

1. A method for improving the performance and stability of perovskite solar cells using ionic liquids, characterized in that, An ionic liquid additive was added to a perovskite precursor solution, and the resulting perovskite film doped with the additive was obtained by spin-coating. The additive's scientific name is 9-bromo-6,7-diphenylpyrido[2,1-a]isoquinolin-5-iumhexafluorophosphate, abbreviated as DPIQ. + PF6 − Its structural formula is: .

2. The method for improving the performance and stability of perovskite solar cells using ionic liquids according to claim 1, characterized in that, By utilizing the passivation effect of the additive on grain boundaries and film surface defects, the defect density of perovskite films is reduced, and the charge extraction efficiency is improved.

3. The method for improving the performance and stability of perovskite solar cells using ionic liquids according to claim 1, characterized in that, The additive is first dissolved in N,N-dimethylformamide and then added to a perovskite precursor solution dissolved in dimethyl sulfoxide.

4. The method for improving the performance and stability of perovskite solar cells using ionic liquids according to claim 1, characterized in that, The optimal concentration of the additive in the perovskite precursor solution is 0.3 mg / ml.

5. The method for improving the performance and stability of perovskite solar cells using ionic liquids according to claim 1, characterized in that, The thermal annealing temperature during the thin film preparation process is 120℃.

6. The method for improving the performance and stability of perovskite solar cells using ionic liquids according to claim 1, 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.

7. A perovskite solar cell prepared by the method according to any one of claims 1 to 6.

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