N-p homojunction all-inorganic perovskite solar cell and preparation method thereof

Abstract

This invention discloses an N-P homojunction all-inorganic perovskite solar cell for indoor photovoltaic applications. This invention provides a method to overcome the efficiency limit of indoor photovoltaics. By treating the interface of an all-inorganic perovskite (CsPbI3) thin film with a surface-modified material (sodium dodecyl sulfate: SDS), a CsPbI3 perovskite thin film with an N-P homojunction is prepared in a glove box. The formation of PbS on the surface is observed using scanning electron microscopy (SEM), and the formation of the N-P homojunction is verified using atomic force microscopy (KPFM). The formation of the N-P homojunction on the CsPbI3 thin film surface solves the bandgap matching problem between the CsPbI3 perovskite thin film and the charge transport layer. Most importantly, J sc Significant improvements have been made, which enhances the performance of all-inorganic perovskite indoor photovoltaics. sc This provides an effective strategy.

Description

Technical Field

[0001] This invention relates to the technical field of indoor photovoltaic solar cells, specifically an NP homojunction all-inorganic perovskite solar cell for indoor photovoltaic applications. Background Technology

[0002] The rapid development of Internet of Things (IoT) technology has led to the widespread adoption of numerous low-power electronic devices. However, these devices require a continuous power supply. Indoor light, as low-intensity light, is considered a viable option for providing continuous power to IoT electronic devices using unique indoor photovoltaics (IPVs). The spectral range of indoor light sources is within the visible range (400-800 nm), thus determining the ideal bandgap range for IPVs to be 1.7-1.9 eV. However, the low intensity of indoor light sources results in poor performance for commercially available photovoltaic devices such as crystalline silicon (c-Si). Surprisingly, perovskite solar cells (PSCs) exhibit higher efficiency under low-intensity indoor light conditions.

[0003] Despite the bandgap mismatch (~1.60 eV) of organic-inorganic halide lead perovskites, numerous studies have reported power conversion efficiencies (PCE) exceeding 40% in the laboratory. However, experiments have shown that most narrow-bandgap perovskite IPVs (PIPVs) have significantly lower short-circuit current densities (J / L). sc The open-circuit voltage (V) has reached its limit, and there is an urgent need to increase it. oc In an increasing number of studies, methods such as passivation defects are beneficial for devices to operate under indoor light sources, but the narrow bandgap leads to V... oc It is still very low. Therefore, while maintaining a narrow bandgap J sc At the same time, wide bandwidth is beneficial for increasing V oc Higher PCE is expected. Because wide-bandgap (~1.70 eV) organic-inorganic hybrid perovskites (OIHPs) typically have shorter diffusion lengths and more severe optical phase segregation, leading to higher PCE values. oc The losses are even greater. All-inorganic perovskites (such as CsPbI3) are one of the most suitable solutions to this problem because of their tunable band gap (1.7~2.3 eV).

[0004] In recent years, the PCE of all-inorganic CsPbI3 perovskite solar cells (PSCs) has also increased rapidly, with our group achieving a PCE of 19.17%. However, the black phase of CsPbI3 perovskite has relatively poor stability and easily transforms into the thermodynamically stable yellow phase (such as δ-CsPbI3). To improve the PCE of CsPbI3 PSCs... scDue to its hydrophobicity, numerous process strategies have been employed to optimize CsPbI3 films, including defect passivation, strain engineering, and crystallinity manipulation. For example, Du et al. effectively reduced defects by introducing novel ionic liquids to passivate iodine vacancies in CsPbI3 films. Ke et al. applied pressure to CsPbI3 films, controlling [PbI6] by adjusting the pressure. 4- The octahedral tilt stabilizes the cubic CsPbI3 structure. Xu et al. modified the buried interface to adjust the crystal quality of CsPbI3, effectively reducing Vc. oc Indeed, these strategies effectively improve the hydrophobicity and PCE of CsPbI3. However, the band matching problem between the CsPbI3 perovskite film and the charge transport layer has been neglected. In recent years, many studies have shown that the surface type (p-type or n-type) of perovskite films can be changed by doping perovskite. Xiong et al. used capsaicin to transform the surface of MAPbI3 from p-type to n-type, enhancing charge transfer and reducing nonradiative losses. Therefore, all-inorganic IPVs can construct CsPbI3 NP homojunctions by doping, improve energy level matching, enhance the internal electric field, and enhance J. sc It is of great significance. Summary of the Invention

[0005] This invention employs an interface modification strategy to introduce sodium dodecyl sulfate (SDS) into a perovskite layer to prepare highly efficient and stable PSCs. Results show that the hydrophobicity of long-chain SDS improves the surface moisture resistance of the CsPbI3 film. Uncoordinated Pb in CsPbI3... 2+ PbS is generated in situ on the perovskite surface through interaction with the sulfate functional group. The unique hole transport properties of PbS increase the surface potential of the perovskite, leading to the spontaneous formation of NP homojunctions in CsPbI3, further accelerating the hole transport efficiency of CsPbI3. 2+ The strong bonds formed between the sulfuric acid functional groups and the perovskite interface, along with the long-chain structure, significantly inhibited the degradation of CsPbI3. This work provides a practical solution for overcoming the efficiency bottleneck of IPVs and PSCs.

[0006] This invention provides an NP homojunction all-inorganic perovskite solar cell for indoor photovoltaic applications, offering a practical solution to overcome the efficiency bottleneck of IPVs and PSCs.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] An NP homojunction all-inorganic perovskite solar cell for indoor photovoltaic applications, with SDS solvent treatment of the perovskite thin film interface.

[0009] The electrostatic potential of SDS was calculated using Gaussian methods. The negatively charged sulfate groups in SDS interact with the uncoordinated Pb groups in CsPbI3. 2 + The Pb-S coordination bonds lead to the formation of PbS on the perovskite surface.

[0010] Next, SEM was used to observe the surface of the CsPbI3 film. A dense PbS layer was formed on the CsPbI3 surface, which obviously played a significant role. PbS is beneficial to carrier transport.

[0011] Next, the migration of ions was examined using time-of-flight mass spectrometry (TOF-SIMS), and it was clearly observed that PbS was passivated in the upper part of the thin film, forming a P-type semiconductor.

[0012] Then, the surface potential of the etched film was tested using KPFM, and a unique verification method was used to prove that the CsPbI3 film spontaneously generated an NP homojunction.

[0013] Finally, the band structure of the thin film was examined using UPS and UV-vis, further verifying the spontaneous formation of NP homojunctions in the CsPbI3 thin film.

[0014] A method for fabricating an NP homojunction all-inorganic perovskite solar cell for indoor photovoltaic applications includes the following steps:

[0015] I. Cleaning and treatment of solar cell substrate: The glass substrate was ultrasonically cleaned in sequence with detergent, deionized water, acetone and ethanol. The cleaned glass substrate was then dried and treated with an ultraviolet plasma cleaner to obtain sample ①.

[0016] II. Preparation of electron transport layer: Sample ① was heated to 70℃, and TiO2 was spin-coated onto the surface of sample ① as the electron transport layer of solar cell using a spin coater. Sample ② was obtained by annealing.

[0017] III. Preparation of the all-inorganic perovskite solution: In a glove box filled with argon, CsI, PbI2 and DMAI were dissolved in DMF and DMSO solvents in a stoichiometric ratio of 1:1:1 to prepare a CsPbI3 perovskite solution. The solution was then filtered to obtain the CsPbI3 solution.

[0018] IV. Preparation of modified material solution: In a glove box filled with argon, sodium dodecyl sulfate (SDS) was stirred and dissolved in chlorobenzene, and the SDS solution was obtained by filtration.

[0019] V. Preparation of NP homojunction perovskite thin film: Sample ② was transferred to an argon-filled glove box by vacuuming, and NP homojunction CsPbI3 thin film was prepared on a spin coater. SDS solution was rapidly added in the middle of spin coating the CsPbI3 thin film, and finally annealed to obtain sample ③.

[0020] VI. Preparation of the hole transport layer: Spiro-OMeTAD solution was spin-coated onto sample ③ to obtain sample ④;

[0021] VII. Electrode Evaporation: Selecting the vapor-deposited Ag electrode as the positive electrode of the battery, the sample ④ is transferred to a rotary evaporator for vapor deposition, thus obtaining a complete perovskite solar cell device.

[0022] In step one, the glass substrate is an ITO conductive glass substrate, and the ultrasonic cleaning time is 10-15 min; the oven drying temperature is 60℃-80℃, and the time is 4-5 h; the power of the ultraviolet plasma cleaner is 60 W, and the time is 60 s.

[0023] In step two, the electron transport layer TiO2 is annealed at 450°C for 1 hour in a fume hood with a rotation speed of 5000 rpm / min and a time of 30 s.

[0024] In step three, perovskite is dissolved in a mixed solution of DMF and DMSO in a volume ratio of 4:1; the stirring time is 5 h using a magnetic stirrer; and a 0.45 μm organic filter head is used for filtration.

[0025] In step four, the concentration of the SDS solution was 9 mmol / mL; the stirring time with a magnetic stirrer was 5 h.

[0026] In step five, the surface spin coating is performed by standing a 50 μL solution of CsPbI3 for spin coating at a speed of 3000 rpm / min for 30 s; the intermediate spin coating refers to adding SDS solution at 15 s; the annealing temperature is 180℃ and the annealing time is 3 min.

[0027] In step six, the Spiro-OMeTAD solution ratio is: 72.3 mg Spiro-OMeTAD, 17.5 μL Li-TFSI / acetonitrile (520 mg / mL). -1 ) and 28.8 μL t-BP (1 mL chlorobenzene solution), spin-coated at a speed of 5000 rpm / min for 30 s.

[0028] In step seven, the vapor deposition conditions for the rotary evaporator are: vacuum degree ≥ 1 × 10⁻⁶. -4 Pa, the thickness of the vapor deposition is 80 nm.

[0029] The present invention has the following advantages:

[0030] SDS passivation on the CsPbI3 film surface successfully improved J sc While maintaining the performance of other devices, it also maintains the high V of all-inorganic solar cells. oc SDS completely covers the surface of the CsPbI3 film, Pb 2+ The strong interaction between SDS and sulfate groups enables in-situ growth of PbS, exhibiting excellent hole transport properties. Furthermore, the long alkyl chains of SDS form a dense network structure, significantly improving the hydrophobicity of CsPbI3. Importantly, an NP homojunction is formed on the CsPbI3 film surface, resolving the bandgap matching issue between the CsPbI3 perovskite film and the charge transport layer. With SDS surface passivation, the PCE reaches 35.2% (1000 lux). Most importantly, J... sc Significant improvements have been made, which enhances the performance of all-inorganic perovskite indoor photovoltaics. sc This provides an effective strategy. Specifically:

[0031] The experimental scheme of this invention prepares an NP homojunction perovskite solar cell by passivating the CsPbI3 film surface with SDS solvent, thereby increasing the surface potential of the CsPbI3 film and enabling the spontaneous formation of NP CsPbI3 perovskite. This film exhibits a higher surface potential, larger grain size, stronger crystallinity, smoother interface, and more pronounced hydrophobicity compared to the unmodified CsPbI3 film with SDS. Therefore, the NP homojunction CsPbI3 perovskite film comprehensively improves the performance of perovskite solar cells. This overcomes the shortcomings of organic-inorganic hybrid perovskite solar cells and promotes the development of CsPbI3 perovskite films in indoor photovoltaic applications.

[0032] 2. The solution provided by this invention is to combine the modified material SDS with the uncoordinated Pb on the surface of the perovskite thin film. 2+ Through interaction, PbS nanocrystals are generated in situ, which can fully cover the perovskite film to improve uniformity, while also controlling the crystallization of the perovskite film.

[0033] 3. The solution provided by this invention is to use the modified material SDS to react with uncoordinated Pb on the surface of the perovskite thin film. 2+ Through interaction, the long alkyl chains of SDS are orderly stacked on the surface of the perovskite thin film. The method of preparation using SDS is unique and greatly improves the lifespan of CsPbI3 solar cells, which has groundbreaking application value in the future industrialization of indoor photovoltaics. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a flowchart illustrating a method for fabricating an NP homojunction all-inorganic perovskite solar cell for indoor photovoltaic applications.

[0036] Figure 2 SDS electrostatic potential in an NP homojunction all-inorganic perovskite solar cell for indoor photovoltaic applications;

[0037] Figure 3 The basic morphological characterization of CsPbI3 prepared in Examples 1 and 2 for an NP homojunction all-inorganic perovskite solar cell for indoor photovoltaic applications is shown.

[0038] Figure 4 The KPFM images of the thin films prepared in Examples 1 and 2 are shown for an NP homojunction all-inorganic perovskite solar cell used in indoor photovoltaics.

[0039] Figure 5 UV-vis images of the thin films prepared in Examples 1, 2, 3, 4, and 5 of an NP homojunction all-inorganic perovskite solar cell for indoor photovoltaic applications;

[0040] Figure 6 The device structure, cross-sectional view, and band diagram of CsPbI3 prepared in Examples 1 and 2 are shown for an NP homojunction all-inorganic perovskite solar cell for indoor photovoltaic applications.

[0041] Figure 7 This study examines the effect of two examples on the stability of cells prepared in Example 1 and Example 2 for an NP homojunction all-inorganic perovskite solar cell intended for indoor photovoltaic applications. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] In one embodiment, see Figure 1-4 ,

[0044] Example 1

[0045] An NP homojunction all-inorganic perovskite solar cell for indoor photovoltaic applications includes the following steps:

[0046] I. Cleaning and treatment of solar cell substrates: The glass substrates were numbered using the initials of the individual's name and arranged in ascending order in the washing rack. The glass substrates were then ultrasonically cleaned in sequence with detergent, deionized water, acetone, and ethanol. After cleaning, the glass substrates were placed in an oven to dry. The dried glass substrates were then treated with an ultraviolet plasma cleaner to obtain sample ①.

[0047] II. Selection and Preparation of the Electron Transport Layer: Titanium dioxide (TiO2) is generally used as the electron transport layer. Based on bandgap matching, we selected titanium dioxide (TiO2) as the electron transport layer. Sample ①, treated with UV plasma cleaning, was coated with a dense TiO2 layer by spraying 0.2 M pyrolytic Ti(IV) ethyl acetate-diisopropoxy in a 1-butanol solution and annealing at 450℃ for 1 h. This process resulted in sample ②.

[0048] III. Preparation of the all-inorganic perovskite solution: A 0.9 M CsPbI3 perovskite precursor was prepared by dissolving stoichiometric CsI, PbI2, and DMAI in DMF at a molar ratio of 1:1:1. The mixture was stirred using a magnetic stirrer in a glove box, and the CsPbI3 solution was obtained by filtration.

[0049] IV. Preparation of the modified material solution: Dissolve sodium dodecyl sulfate (SDS) in chlorobenzene (3 mmol / mL), stir with a magnetic stirrer in a glove box, and obtain the SDS solution by filtration;

[0050] V. Preparation of NP homojunction perovskite thin film: Sample ② was transferred to a glove box by vacuuming, and NP homojunction CsPbI3 thin film was prepared on a spin coater. The CsPbI3 perovskite layer was spin-coated onto an ITO / TiO2 substrate (sample ②) preheated at 70℃ (3000 rpm, 30 s). SDS solution was rapidly added dropwise in the middle of spin-coating the CsPbI3 film. Finally, the film was annealed at 210℃ for 5 min to obtain sample ③.

[0051] VI. Selection and Preparation of Hole Transport Layer: Hole transport layers are generally made of poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate (PEDOT: PSS) and 2,2',7,7"-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene (Spiro-OMeTAD). Based on performance testing, Spiro-OMeTAD was selected as the hole transport layer. 72.3 mg / mL -1 Spiro-OMeTAD, 17.5 μL Li-TFSI / acetonitrile (520 mg / mL) -1 ) and 28.8 μL t-BP (1 mL chlorobenzene solution) were spin-coated onto sample ③ at a speed of 5000 rpm / 30 s to obtain sample ④.

[0052] VII. Electrode Selection and Evaporation: Gold (Au) and silver (Ag) are generally used as candidate materials for electrodes. By comparing work functions, an Ag electrode was selected as the positive electrode of the battery. Sample ④ was transferred to a rotary evaporator for evaporation. At a constant evaporation rate of 0.3 Å / s, an 80 nm thick Ag film was prepared by thermal evaporation, thus obtaining a complete perovskite solar cell device.

[0053] Example 2

[0054] The difference between Example 2 and Example 1 is that SDS-modified material is not added in step five.

[0055] Example 3

[0056] The difference between Example 3 and Example 1 is that in step five, SDS is dissolved in chlorobenzene (6 mmol / mL).

[0057] Example 4

[0058] The difference between Example 4 and Example 1 is that in step five, SDS is dissolved in chlorobenzene (9 mmol / mL).

[0059] Example 5

[0060] The difference between Example 5 and Example 1 is that in step 5, SDS is dissolved in chlorobenzene (12 mmol / mL).

[0061] Calculate the electrostatic potential of SDS in Example 1 (see Figure 2 It can be seen that the negatively charged sulfate groups in SDS are uncoordinated with the Pb groups in CsPbI3. 2+ The Pb-S coordination bonds lead to the formation of PbS on the perovskite surface.

[0062] The morphologies of the perovskite films prepared in Example 1 and Example 2 were compared (see...). Figure 3As can be seen from Example 1, SDS modified the surface of the CsPbI3 thin film, forming PbS nanocrystals that are beneficial for hole transport and higher photovoltaic performance.

[0063] The KPFM of the perovskite thin films prepared in Example 1 and Example 2 were compared (see...). Figure 4 As can be seen from Example 1, SDS modified the surface of the CsPbI3 film, proving that the CsPbI3 film spontaneously generates NP homojunctions.

[0064] The UV-vis of the perovskite thin films prepared in Examples 1, 2, 3, 4, and 5 were compared (see Example 5). Figure 5 As can be seen from Example 1, SDS modified the surface of the CsPbI3 film, verifying that the CsPbI3 film spontaneously generates NP homojunctions.

[0065] The perovskite films prepared in Examples 1 and 2, exhibiting typical planar nip-type PSCs layer-by-layer structures, were confirmed by cross-sectional scanning electron microscopy (see Example 1). Figure 6 The CsPbI3 & SDS layer has a thickness of approximately 428 nm and a uniform morphology. This indicates that the energy level arrangement of the NP homojunction greatly promotes charge transfer between CsPbI3 and Spiro-OMeTAD, and reduces charge recombination.

[0066] The stability of the cells was tested using the preparation methods of Examples 1 and 2, respectively. Clearly, the PCE of the CsPbI3 & SDS perovskite solar cell device exceeded 90% after 1000 h, while the PCE of the CsPbI3 perovskite solar cell device was only around 30% after 500 h. These results indicate that the SDS passivation strategy is an effective method to improve the hydrophobicity of CsPbI3 perovskite solar cell devices. (See...) Figure 7 .

[0067] This invention relates to an NP homojunction all-inorganic perovskite solar cell for indoor photovoltaic applications. An interface modification strategy is employed to introduce sodium dodecyl sulfate (SDS) into the perovskite layer to prepare a high-efficiency and stable perovskite solar cell device. Results show that the hydrophobicity of the long-chain SDS improves the surface moisture resistance of the CsPbI3 film. Uncoordinated Pb in CsPbI3... 2+ PbS is generated in situ on the perovskite surface through interaction with the sulfate functional group. The unique hole transport properties of PbS increase the surface potential of the perovskite, leading to the spontaneous formation of NP homojunctions in CsPbI3, further accelerating the hole transport efficiency of CsPbI3. 2+Strong bonds are formed between the sulfuric acid functional group and the perovskite interface, and the long-chain structure greatly inhibits the degradation of CsPbI3. Under conditions of 20-30% relative humidity, the unencapsulated perovskite solar cell device maintains more than 90% PCE within 1000 hours.

[0068] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for fabricating an NP homojunction all-inorganic perovskite solar cell for indoor photovoltaic applications, characterized in that: The following options are included: I. Cleaning and treatment of solar cell substrate: The glass substrate was ultrasonically cleaned in sequence with detergent, deionized water, acetone and ethanol. The cleaned glass substrate was then dried and treated with an ultraviolet plasma cleaner to obtain sample ①. II. Preparation of electron transport layer: Sample ① was heated to 70℃, and TiO2 was spin-coated onto the surface of sample ① as the electron transport layer of solar cell using a spin coater. Sample ② was obtained by annealing. III. Preparation of the all-inorganic perovskite solution: In a glove box filled with argon, CsI, PbI2 and DMAI were dissolved in DMF and DMSO solvents in a stoichiometric ratio of 1:1:1 to prepare a CsPbI3 perovskite solution. The solution was then filtered to obtain the CsPbI3 solution. IV. Preparation of modified material solution: In a glove box filled with argon, sodium dodecyl sulfate (SDS) was stirred and dissolved in chlorobenzene, and the SDS solution was obtained by filtration. V. Preparation of NP homojunction perovskite thin film: Sample ② was transferred to an argon-filled glove box by vacuuming, and NP homojunction CsPbI3 thin film was prepared on a spin coater. SDS solution was rapidly added in the middle of spin coating the CsPbI3 thin film, and finally annealed to obtain sample ③. VI. Preparation of the hole transport layer: Spiro-OMeTAD solution was spin-coated onto sample ③ to obtain sample ④; VII. Electrode Evaporation: Selecting the vapor-deposited Ag electrode as the positive electrode of the battery, the sample ④ is transferred to a rotary evaporator for vapor deposition, thus obtaining a complete perovskite solar cell device.

2. The method for preparing an NP homojunction all-inorganic perovskite solar cell for indoor photovoltaic applications according to claim 1, characterized in that: In step one, the glass substrate is an ITO conductive glass substrate, and the ultrasonic cleaning time is 10-15 min; the oven drying temperature is 60℃-80℃, and the time is 4-5 h; the power of the ultraviolet plasma cleaner is 60W, and the time is 60 s.

3. The method for preparing an NP homojunction all-inorganic perovskite solar cell for indoor photovoltaic applications according to claim 1, characterized in that: In step two, the electron transport layer TiO2 is annealed at 450°C for 1 hour in a fume hood with a rotation speed of 5000 rpm / min and a time of 30 s.

4. The method for preparing an NP homojunction all-inorganic perovskite solar cell for indoor photovoltaic applications according to claim 1, characterized in that: In step three, perovskite is dissolved in a mixed solution of DMF and DMSO in a volume ratio of 4:1; the stirring time is 5 h using a magnetic stirrer; and a 0.45 μm organic filter head is used for filtration.

5. The method for preparing an NP homojunction all-inorganic perovskite solar cell for indoor photovoltaic applications according to claim 1, characterized in that: In step four, the concentration of the SDS solution was 9 mmol / mL; the stirring time with a magnetic stirrer was 5 h.

6. The method for preparing an NP homojunction all-inorganic perovskite solar cell for indoor photovoltaic applications according to claim 1, characterized in that: In step five, the surface spin coating is performed by standing a 50 μL solution of CsPbI3 for spin coating at a speed of 3000 rpm / min for 30 s; the intermediate spin coating refers to adding SDS solution at 15 s; the annealing temperature is 180℃ and the annealing time is 3 min.

7. The method for preparing an NP homojunction all-inorganic perovskite solar cell for indoor photovoltaic applications according to claim 1, characterized in that: In step seven, the vapor deposition conditions for the rotary evaporator are: vacuum degree ≥ 1 × 10⁻⁶. -4 Pa, the thickness of the vapor deposition is 80 nm.

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