CN106384785A - Tin-doped CH3NH3SnxPb1-xI3 perovskite solar cell - Google Patents

Abstract

The invention relates to the field of solar cells, in particular to an organic-inorganic hybrid perovskite solar cell. A tin-doped methylammonium lead iodide perovskite solar cell, the active layer is a tin-doped methylammonium lead iodide perovskite CH ₃ NH ₃ Sn _x Pb _1‑x I ₃ thin film, this Invented tin-doped methylammonium-based lead iodide perovskite solar cells have a planar heterojunction structure, and the present invention proposes a one-step process assisted by multi-step solvent treatment to prepare CH ₃ NH ₃ Sn _x Pb _1‑x I ₃ The method of perovskite solar cells obtains high-quality perovskite films and achieves high photoelectric conversion efficiency.

Description

A tin-doped methylammonium lead iodide perovskite solar cell

technical field

The invention relates to the field of solar cells, in particular to an organic-inorganic hybrid perovskite solar cell.

Background technique

The light absorption layer of perovskite solar cells is an organic-inorganic hybrid perovskite material with the chemical formula AMX ₃ (A: CH ₃ NH ³⁺ ; M: IVA group Pb, Sn mixed elements; X: halogen group element), the unit cell structure MX ₆ constitutes an octahedron and contacts each other, forming a three-dimensional structure in which NH ₃ CH ³⁺ is embedded. The development of perovskite solar cells is of great significance to the large-scale use of solar energy to provide cheap electricity. At present, the biggest problem of tin-doped methylammonium lead iodide perovskite solar cells is low photoelectric conversion efficiency and poor stability, which cannot meet the needs of commercial applications. A key solution to improve the photoelectric conversion efficiency of this type of cell is to improve the film quality of the light-absorbing layer of the cell. The use of a thick active layer can ensure the light absorption of the cell, but the quality of the film is difficult to guarantee, which is not conducive to the transport and effective collection of carriers. This problem can be effectively solved by preparing the active layer film by two-step method, that is, by using two-step spin coating method, by adjusting the annealing temperature and annealing time, and controlling the solution concentration at the same time to improve the quality of crystal growth and promote the transport and collection of carriers. , while enhancing the light absorption of the active layer, thereby realizing highly efficient tin-doped methylammonium lead iodide perovskite solar cells. For example, in 2014, Feng Hao et al. designed a tin-doped methylammonium lead iodide perovskite cell with mesoporous TiO ₂ as the electrode and spiro-OMeTAD as the hole transport material, so that the tin doping ratio was 25%. (ie CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ ) the photoelectric conversion efficiency of the battery reached 7.37%, and the battery with a tin-doped ratio of 50% (ie CH ₃ NH ₃ Sn _0.5 Pb _0.5 I ₃ ) reached 7.27% [J . Am. Chem. Soc. 2014, 136, 8094−8099]; In 2016, Leize Zhu, et al. used a two-step method and DMSO annealing assistance to achieve a photoelectric conversion efficiency of 10.25% for a cell doped with 10% tin [Nanoscale , 2016,8, 7621-7630]; In July 2016, Yunlong Li et al. also adopted a two-step method to achieve a photoelectric conversion efficiency of 13.6% for tin-lead perovskite cells with a tin-doped ratio of 50%【Adv.Energy Mater . 2016, 1601353], making the efficiency of tin-lead perovskite solar cells reach a new height. The above literatures all use a two-step method to fabricate tin-doped methylammonium-based lead iodide perovskite solar cells. These reports point out that only the two-step method can ensure the quality of the battery film, including the crystallinity, density and thickness of the film. The flatness of the surface, etc., and it is impossible to obtain a high-quality battery film by one-step preparation. Although a higher photoelectric conversion efficiency has been obtained by using the two-step method, the experimental production process is too cumbersome, which not only wastes a lot of time but also consumes a lot of resources, resulting in high production costs and is not environmentally friendly. The present invention proposes to use a one-step method and multi-step solvent treatment to manufacture tin-doped methylammonium lead iodide perovskite batteries, so that the highest efficiency of batteries with a tin-doped ratio of 25% reaches 12.08%. This invention is fast The low-cost preparation of this type of battery provides an effective solution, which is of great significance for promoting the commercial application of this type of battery.

Contents of the invention

The technical problem to be solved by the invention is: how to manufacture tin-doped methylammonium lead iodide perovskite battery by one-step method.

The technical solution adopted in the present invention is: a tin-doped methylammonium lead iodide perovskite solar cell, a glass substrate with a uniform layer of indium tin oxide ITO is deposited as the anode of the battery, and the indium tin oxide A layer of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate PEDOT:PSS film was deposited on the glass substrate of ITO as a hole transport layer, and the poly(3,4-ethylenedioxythiophene)-poly An active layer was deposited on the PEDOT:PSS thin film of styrene sulfonate, and then a layer of [6,6]-phenyl C60-butyric acid methyl ester PC ₆₀ BM was spin-coated on the active layer as an electron transport layer, and finally A continuous aluminum or silver film is deposited as the cathode of the battery by vacuum thermal evaporation, and the active layer is tin-doped methylammonium lead iodide perovskite CH ₃ NH ₃ Sn _x Pb _1-x I ₃ film, x is a positive number less than 1. The tin-doped methylammonium lead iodide perovskite solar cell of the present invention has a planar heterojunction structure.

As a preferred mode: the process of depositing one layer of active layer is: methyl ammonium iodide CH ₃ NH ₃ I, lead iodide PbI ₂ and tin iodide SnI ₂ are 1.08:(1- x ) according to the molar ratio: x is dissolved in a mixed solvent of N, N-dimethylformamide DMF and dimethyl sulfoxide DMSO to form a precursor solution. In the precursor solution, the molar concentration of methyl ammonium iodide CH ₃ NH ₃ I is 1.62 mol/L, The volume ratio of N,N-dimethylformamide DMF and dimethyl sulfoxide DMSO is 10:1, utilize solution spin-coating method on poly(3,4-ethylenedioxythiophene)-polystyrenesulfonic acid PEDOT: Spin-coat the precursor solution on the PSS film, the spin-coating rate is 6000-6500 rpm, and the spin-coating time is 30-40s. Add sec-butanol to clean, the time to start cleaning is 5-15s after the start of spin coating, and the cleaning time is 1-1.5s. After the above process is completed, keep the temperature at 100 ° C for 25 s in the _N2 atmosphere, and then use Soak in sec-butanol for 5-10 s, the glass substrate is in a static state during the soaking period, rotate the glass substrate after soaking, the rotation speed is 6000-6500 rpm, the rotation time is 25-35s, and then maintain the temperature at 100 °C in the _N2 atmosphere for annealing 25 min, and finally annealed under DMF hot steam for 25 min, the annealing temperature was still maintained at 100 °C, and finally a tin-doped methylammonium lead iodide perovskite CH ₃ with a film thickness of 290 nm - 310 nm was produced NH ₃ Sn _x Pb _1-x I ₃ thin films.

In the process of preparing CH ₃ NH ₃ Sn _x Pb _1-x I ₃ perovskite film in one step, the present invention uses a multi-step solvent treatment process, including organic reagent sec-butanol cleaning and soaking process, and N ₂ atmosphere DMF solvent annealing process. In the process of spin-coating CH ₃ NH ₃ Sn _x Pb _1-x I ₃ perovskite films, sec-butanol was used to replace the traditional toluene and chlorobenzene to clean the active layer, which accelerated the transition from liquid phase to solid state. The phase transformation improves the crystallization speed of the active layer; soaking the active layer with sec-butanol after pre-annealing also greatly promotes the flatness of the active layer film, which helps to improve the current intensity of the battery. Excessive ammonium iodide has been used in the configuration process, soaking with sec-butanol also helps to remove excess ammonium iodide; sec-butanol used in the present invention is compared with traditionally used toluene, chlorobenzene, Low cost and low toxicity; DMF solvent annealing process under N ₂ atmosphere helps to form large-grain, dense CH ₃ NH ₃ Sn _x Pb _1-x I ₃ perovskite films. Compared with the existing one-step method for preparing CH ₃ NH ₃ Sn _x Pb _1-x I ₃ perovskite thin films, the CH ₃ NH ₃ Sn _x Pb _1-x I ₃ perovskite thin films prepared by the present invention have more grains Larger, denser, higher crystallinity and flatness, so the photoelectric conversion efficiency of the prepared CH ₃ NH ₃ Sn _x Pb _1-x I ₃ perovskite solar cells is much higher than the existing technology [see Adv. Energy Mater. 2016, 1601353]. Compared with the existing two-step method for preparing CH ₃ NH ₃ Sn _x Pb _1-x I ₃ perovskite thin films [see Nanoscale, 2016, 8, 7621-7630], the production process is simplified and the production time is saved. The production cost is reduced. Moreover, the CH ₃ NH ₃ Sn _x Pb _1-x I ₃ perovskite solar cell prepared by the present invention is compared with the prior art [see Adv. Energy Mater. 2016, 1601353, Nanoscale, 2016, 8, 7621-7630] , has a simpler structure, mainly because the cathode buffer layer is omitted. In a word, the performance of the present invention is superior to that of CH ₃ NH ₃ Sn _x Pb _1-x I ₃ perovskite solar cells prepared by the existing one-step method, and is superior to the CH ₃ prepared by the existing two-step method in terms of preparation technology. NH ₃ Sn _x Pb _1-x I ₃ perovskite solar cells.

As a preferred method: the thickness of the glass substrate of indium tin oxide ITO is 100 nm, and the thickness of the hole transport layer poly(3,4-ethylenedioxythiophene)-polystyrenesulfonic acid PEDOT:PSS is 30 nm-40 nm, spin-coating rate 3000rpm during deposition, spin-coating time 30-40 s, after deposition, keep annealing temperature 120 ° C in air, annealing time 10-15 min, electron transport layer thickness 40 nm-50 nm, spin The coating rate is 2800 rpm, the spin coating time is 30-40 s, the cathode layer thickness is 150 nm, and the evaporation rate is 0.5 nm/s.

The beneficial effects of the present invention are: the present invention proposes a method for preparing CH ₃ NH ₃ Sn _x Pb _1-x I ₃ perovskite solar cells using a multi-step solvent treatment-assisted one-step method, and obtains high-quality perovskite thin film, achieving high photoelectric conversion efficiency. The invention adopts a one-step method to simplify the operation process of the existing two-step method, saves production time and reduces production costs; the invention uses sec-butanol instead of traditional toluene and chlorobenzene as cleaning and soaking solvents, which is not only low in cost , and low toxicity and environmental protection.

Description of drawings

Fig. 1 is a structural schematic diagram of a solar cell of the present invention;

Figure 2 is the scanning electron micrograph (SEM) of the CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ film and its cross-section washed with sec-butanol and not washed with sec-butanol, where a is CH ₃ NH ₃ washed with sec-butanol SEM image of Sn _0.25 Pb _0.75 I ₃ film, c is the SEM image of the cross-section of CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ film after cleaning with sec-butanol, b is CH ₃ NH ₃ without cleaning with sec-butanol The SEM image of the Sn _0.25 Pb _0.75 I ₃ film, d is the SEM image of the cross-section of the CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ film without cleaning with sec-butanol;

Fig. 3 X-ray diffraction spectrum (XRD) of CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ films cleaned and not cleaned by sec-butanol, a represents the XRD pattern of CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ films not cleaned, b represents the XRD pattern of the CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ film after washing with sec-butanol;

Figure 4 is the SEM image of the CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ film under different annealing conditions, a represents the CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ perovskite film in the N ₂ atmosphere at a temperature of 100 °C SEM image of the CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ film formed by thermal annealing for 25 min, and then annealing under DMF hot steam at 100 °C for 25 min; b represents CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ SEM image _{of perovskite} film _annealed in air at 100 °C for ₂₅ min, then annealed in DMF hot steam at 100 °C for 25 min _; c Representative SEM _{images of} CH ₃ NH ₃ Sn _0.25 Pb _0.75 I _{3 perovskite} films formed by thermal annealing at 100 °C for ₂₅ min in N ₂ atmosphere _;

Figure ₅ is the X-ray diffraction spectrum (XRD _{) of CH 3} NH ₃ Sn _0.25 Pb _0.75 I _{3 films} under different annealing conditions _. XRD pattern of CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ film formed by thermal annealing at 100 °C for 25 min, and then annealing in DMF hot steam at 100 °C for 25 min; b represents CH ₃ NH ₃ Sn _0.25 XRD patterns of CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ thin films formed by thermal annealing of Pb _0.75 I ₃ perovskite thin films at 100 °C for 25 min in N ₂ atmosphere. c represents CH ₃ NH 3 NH 3 NH 3 NH 3 perovskite film formed by thermal annealing of CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ perovskite film in air at 100 °C for 25 min, and then in DMF hot steam at 100 °C for 25 min XRD pattern of ₃ Sn _0.25 Pb _0.75 I ₃ film;

Figure 6 is the current-voltage curve of CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ perovskite solar cells. The open circuit voltage of the cell is 0.77 V, the short circuit current density is 24 mA/cm ² , the fill factor is 66%, and the photoelectric conversion efficiency is 12.08 %;

Figure 7 is the external quantum efficiency curve of CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ perovskite solar cells;

Among them, 1. Indium tin oxide ITO glass substrate, 2. Poly(3,4-ethylenedioxythiophene)-polystyrenesulfonic acid (PEDOT:PSS) film, 3. Tin-doped methylammonium iodide Lead perovskite (CH ₃ NH ₃ Sn _x Pb _1-x I ₃ ) film, 4, [6,6]-phenyl C60-butyric acid methyl ester (PC ₆₀ BM) layer, 5, aluminum film or silver membrane.

detailed description

As shown in Figure 1, the tin-doped methylammonium-based lead iodide perovskite solar cell has a planar heterojunction structure: the structure of the solar cell in this embodiment is: ITO/PEDOT:PSS/ CH ₃ NH ₃ Sn _x Pb _1-x I ₃ /PC ₆₀ BM/Al.

In the battery structure, the thickness of the ITO anode is 100 nm, and the sheet resistance is 10Ω.

In the battery structure, the thickness of the hole transport layer PEDOT:PSS is 30 nm, which is formed by solution spin coating and then annealed in air. The spin coating rate is 3000 rpm, the spin coating time is 30 s, the annealing temperature is 120 °C, and the annealing time is 10 minutes,

In the battery structure, the active layer is CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ perovskite film, which is made of methyl ammonium iodide (CH ₃ NH ₃ I), lead iodide (PbI ₂ ) and tin iodide (SnI ₂ ) was dissolved in a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) according to the molar ratio of 1.08:0.25:0.75, and then made by a spin-coating process combined with a multi-step solvent treatment process of.

In the battery structure, the electron transport material is composed of a fullerene derivative [6,6]-phenyl C ₆₀ -butyric acid methyl ester (PC ₆₀ BM), which is prepared by a solution spin coating method with a spin coating rate of 2800 rpm. The time is 30 s, the film thickness is 40 nm,

In the battery structure, the cathode is made of Al film, prepared by vacuum thermal evaporation method, the film thickness is 150 nm, and the evaporation rate is 0.5 nm/s.

Spin-coat CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ precursor solution on ITO/PEDOT:PSS substrate by solution spin coating method, and prepare CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ perovskite film with uniform thickness in one step , the spin-coating rate was 6300 rpm, and the spin-coating time was 35 s. During this spin, sec _- butanol was added dropwise to wash once. The amount of sec-butanol was 300 µl. Pre-annealed at 100 °C for 25 s, then soaked in 300 μl of sec-butanol for 8 s, then spin-coated at 6300 rpm for 30 s, and then placed on the hot stage in N ₂ atmosphere , Thermal annealing at 100 °C for 25 min, followed by annealing in DMF hot steam for 25 min, the annealing temperature was still maintained at 100 °C, and the final film thickness was 300 nm.

The CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ perovskite precursor is composed of methyl ammonium iodide (CH ₃ NH ₃ I), lead iodide (PbI ₂ ) and tin iodide (SnI ₂ ) according to 1.08: 0.25:0.75 molar ratio dissolved in N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) mixed solvent to form a golden yellow solution.

The volume ratio of the N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) mixed solvent is 10:1,

The molar concentration of CH ₃ NH ₃ I is 1.62 mol/L, the molar concentration of tin iodide (SnI ₂ ) is 0.375 mol/L, and the molar concentration of lead iodide (PbI ₂ ) is 1.125 mol/L,

The sec-butanol cleaning process is carried out during the process _of spin _- coating CH ₃ NH ₃ Sn _0.25 Pb _0.75 I _{3 perovskite film .} The timing of the film starts, and cleaning with sec-butanol starts at 13 s, and the cleaning process is completed within 1 s. The comparison of CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ films with butanol cleaning and no cleaning is shown in Figure 2 and Figure 3 .

The sec-butanol immersion process is carried out after spin-coating CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ perovskite film and pre-annealing for ₂₅ s at a temperature of 100 °C in an N atmosphere. The CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ perovskite thin film was kept still and soaked for 8 s.

The annealing process is composed of three annealing processes successively. The first time is to wash the CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ perovskite film with sec-butanol in an N ₂ atmosphere at a temperature of 100° Pre-annealing was carried out at C for 25 s, and the second annealing process was to spin-coat the CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ perovskite film soaked in sec-butanol in N ₂ atmosphere at 100 °C The thermal annealing was performed for 25 min, followed by the third annealing, which was annealed in N ₂ atmosphere and DMF hot steam at a temperature of 100 °C for 25 min. CH ₃ NH ₃ Sn _0.25 Pb _0.75 I ₃ thin films under different annealing conditions are shown in the figure 4 and Figure 5.

The performance diagrams of tin-doped methylammonium lead iodide perovskite solar cells prepared by the present invention are shown in Figure 6 and Figure 7, it can be seen that the present invention has obtained high-quality perovskite films and realized high photoelectricity Conversion efficiency.

Claims (3)

1. A tin-doped methylammonium lead iodide perovskite solar cell is characterized in that: the glass substrate of a uniform indium tin oxide ITO is deposited as the anode of the battery, and the glass substrate of the indium tin oxide ITO A layer of poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate PEDOT:PSS film was deposited on the substrate as a hole transport layer, and the poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate An active layer was deposited on the acid PEDOT:PSS film, and then a layer of [6,6]-phenyl C60-butyric acid methyl ester PC ₆₀ BM was spin-coated on the active layer as an electron transport layer, and finally heated by vacuum Evaporate a continuous layer of aluminum or silver film as the cathode of the battery, the active layer is a tin-doped methylammonium lead iodide perovskite CH ₃ NH ₃ Sn _x Pb _1-x I ₃ thin film, x is less than A positive number of 1. 2. A tin-doped methylammonium lead iodide perovskite solar cell according to claim, characterized in that: the process of depositing an active layer is: methylammonium iodide CH ₃ NH ₃ I , lead iodide PbI ₂ and tin iodide SnI ₂ according to the molar ratio of 1.08:(1- x ): x are dissolved in N,N-dimethylformamide DMF and dimethyl sulfoxide DMSO mixed solvent to form a precursor solution , in the precursor solution, the molar concentration of methyl iodide ammonium CH ₃ NH ₃ I is 1.62 mol/L, and the volume ratio of N,N-dimethylformamide DMF and dimethyl sulfoxide DMSO is 10:1, using The solution spin coating method spins the precursor solution on the poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate PEDOT:PSS film, the spin coating speed is 6000-6500 rpm, and the spin coating time is 30-40s. When the spin-coating precursor is kept for 5-15s after the start of spin-coating, add sec-butanol to clean it for 1-1.5s. After cleaning, continue to spin-coat the precursor solution until the spin-coating time of the precursor solution is completed , annealed at 100 °C for 25 s in a N ₂ atmosphere, then soaked in sec-butanol for 5-10 s, in a static state during soaking, and rotated the glass substrate after soaking, with a rotational speed of 6000-6500 rpm and a rotational time of 25- 35 s, then annealed at 100 °C for 25 min in _N2 atmosphere, and finally annealed for 25 min under DMF hot steam, the annealing temperature was still maintained at 100 °C, and finally produced tin with a film thickness of 290 nm - 310 nm Doped methylammonium lead iodide perovskite CH ₃ NH ₃ Sn _x Pb _1-x I ₃ thin films. 3. a kind of tin-doped methylammonium lead iodide perovskite solar cell according to claim 1, is characterized in that: the glass substrate thickness of indium tin oxide ITO is 100 nm, and hole transport layer poly( 3, 4-Ethylenedioxythiophene)-polystyrene sulfonate PEDOT:PSS has a thickness of 30 nm-40 nm, a spin-coating rate of 3000 rpm, and a spin-coating time of 30-40 s during the deposition process. Keep the annealing temperature at 120 °C, the annealing time is 10-15 min, the thickness of the electron transport layer is 40 nm-50 nm, the spin-coating rate is 2800 rpm, the spin-coating time is 30-40 s, the thickness of the cathode layer is 150 nm, and the evaporation rate is 0.5 nm/s.