RU2737774C1 - Method for chemical deposition of perovskites from gas phase for production of photovoltaic devices, light-emitting diodes and photodetectors - Google Patents

Abstract

FIELD: optics; technological processes.

SUBSTANCE: invention relates to the technology of producing perovskite structures for thin-film optoelectronic devices in technological processes for producing light-emitting diodes, solar cells and photodetectors with a spectral range from 400 to 780 nm, a forbidden zone from 3.1 to 1.57 eV. Method of chemical deposition of solid films with perovskite structure with structural formula ARbX₃ for production of photovoltaic devices, light-emitting diodes and photodetectors, where A is a cation in form of CH₃NH₃ ⁺, or (NH₂)₂CH⁺, or C(NH₂)₃ ⁺, or Cs⁺, or a mixture thereof, X is an anion in form of Cl^-, or Br^-, or I^- or mixture thereof, from a gas phase, consists in grinding the synthesis components of AX and PbX₂ in a molar ratio in range of 1:4 to 1:1 in a ball mill in 12-cycle mode for 5 minutes at 400 rpm until formation of a stoichiometric compound, subsequent loading of the grinding products in the heating and evaporation zone of the synthesis components, placing the flat substrate in the heating zone and depositing the synthesis products, providing pressure of 10 Pa in reaction volume and flow of transportation gas in direction from heating zone of reaction components to reaction products deposition zone, increasing temperature in heating zone until evaporation of synthesis components, increasing temperature in reaction products deposition zone, formation of a photoactive perovskite photoluminescent layer by chemical deposition from a gas phase on a substrate in the zone of deposition of synthesis products at a temperature raised to 305 °C and maintained until completion of the process.

EFFECT: technical result consists in simplification of production process, namely single-step and low-waste technology without use of solvents, adapted to batch production and suitable for making wide-format films with a perovskite structure on a flat substrate with area of up to 1 m², which enables to scale the size of devices from 0_1 cm² to 1 m².

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Description

Technology area

The claimed invention relates to a technology for producing perovskite structures for thin-film optoelectronic devices, and can be used in technological processes for the production of LEDs, solar cells and photodetectors.

State of the art

There is a known technology for producing thin films of perovskite based on bismuth Bi ₂ (MA) ₃ I ₉ (US 2019/0074439 A1, published on March 7, 2019), where it is proposed to simultaneously spray separate powders of methylamine iodine (CH ₃ NH ₃ I) and bismuth iodide ( BiI ₃ ) from different temperature zones of the furnace in an argon atmosphere without using a vacuum. Obtaining the desired perovskite phase is demonstrated. The possibility of applying the technology when deposited on such substrates as ITO, oriented polished silicon is approved.

The disadvantage of this technology is the low output characteristics of devices based on the obtained layer with the Al / Bi ₂ (MA) ₃ I ₉ / Al structure due to the use of perovskite without a lead composition.

Known technology for producing perovskite films based on formamidinium by CVD (US 2017/0268128 A1, published 09.21.2017). The method implements the technologies for creating perovskite films with variable halides. Solar cells constructed using perovskite produced by this technology demonstrate an efficiency of 11.8%.

The disadvantage of this technology is the multistage process, which consists of preliminary thermo-resistive sputtering of lead halides on substrates and subsequent chemical vapor deposition to obtain a perovskite structure, which greatly complicates the technological process.

Known technology for producing films CsPbBr ₃ (Tian C. et al. Chemical Vapor Deposition Method Grown All-Inorganic Perovskite Microcrystals for Self-Powered Photodetectors // ACS applied materials & interfaces. - 2019. - T. 11. - No. 17. - Pp. 15804-15812.), Describing the one-step synthesis of a CsPbBr ₃ film in a vacuum and argon atmosphere on GaN substrates. The paper proposes to use technology for the design of photodetectors, implemented due to the high stability of inorganic perovskite and low leakage current density of the order of 10-5 mA / cm ² .

The disadvantage of this technology is the use of highly crystalline GaN as a substrate, and as a consequence of the difficulty in using the technology in solar cells and photodiodes of the third generation.

The closest to the proposed method is the technology of obtaining perovskite films based on Bi (Sanders S. et al. Chemical vapor deposition of organic-inorganic bismuth-based Perovskite films for solar cell application // Scientific reports. - 2019. - T. 9. - No. 1. - C. 1-8.), In which the relationship between the morphology of the phase composition and the ratio of the starting components MAI and BiI ₃ , based on an eight-fold excess of the organic precursor MAI, leads to an optimal morphology. The CVD system design is scalable for mass production. Solar cells manufactured using this technology have a solar energy conversion efficiency of 0.02%.

The disadvantage of this technology is the low thickness of perovskite films, which does not allow the creation of solar cells with an optimal degree of light absorption. The reason for the low efficiency of solar devices using this technology can be optimization problems, the wrong choice of the structure of the solar cell.

The essence of the invention

The technical result of the claimed technological solution is to provide the possibility of forming a photoactive perovskite layer with a thickness of 8 nm to 8000 nm, a photoluminescence peak in the visible spectral range from 400 to 780 nm with a quantum yield of 2 to 40% by implementing a simplified, one-stage, scalable and low-waste technological process.

The technical result is achieved as follows.

In the method of chemical deposition of continuous films with a perovskite structure with the structural formula APbX ₃ for the production of photovoltaic devices, LEDs and photodetectors, where A is a cation in the form of CH ₃ NH ₃ ⁺ or (NH ₂ ) ₂ CH ⁺ or C (NH ₂ ) ₃ ⁺ or Cs ⁺ or their mixtures, X is an anion in the form of Cl ^- or Br ^- or I ^- or their mixture, from the gas phase, the components of the synthesis AX and PbX _{2 are} milled in a molar ratio in the range from 1: 4 to 1: 1 in ball mill in the mode of 12 cycles of 5 minutes at 400 rpm until a stoichiometric compound is formed, the grinding products are loaded in the zone of heating and evaporation of the synthesis components, and a flat substrate is placed in the zone of heating and precipitation of synthesis products. Then, a pressure of 10 Pa is provided in the reaction volume and a flow of the transport gas in the direction from the heating zone of the reaction components to the zone of precipitation of reaction products with an increase in temperature in the heating zone until the evaporation of the synthesis components, the temperature in the zone of precipitation of reaction products is increased and a photoactive perovskite photoluminescent layer is formed by chemical deposition from the gas phase on a substrate in the zone of deposition of synthesis products at a temperature increased to 305 ° C and maintained until the end of the process.

The invention is illustrated by a drawing, where figure 1 shows a diagram of an installation for chemical vapor deposition of perovskites; figure 2 shows a diffractogram of a film obtained by chemical vapor deposition of CsBr and PbBr ₂ , including phases corresponding to the structure of perovskite CsPbBr ₃ and CsPb ₂ Br ₅ ; Figure 3 shows the photoluminescence spectrum of a film obtained by chemical vapor deposition of CsBr and PbBr ₂ with a peak at 524 nm; Figure 4 shows a diagram of optoelectronic devices with a photoactive layer obtained by chemical vapor deposition of perovskites for the production of photovoltaic devices, LEDs and photodetectors.

The method is carried out on an installation for the chemical deposition of perovskites from the gas phase (Fig. 1), which consists of an open corundum container 1 for loading synthesis components, synthesis components 2, zone 3 for heating and evaporation of synthesis components, zone 4 for heating substrates for deposition of synthesis products, a substrate 5 with a synthesis product.

The structure of optoelectronic devices with a photoactive layer obtained by chemical vapor deposition of perovskites (Fig. 4), contains a layer 6 of a transparent, conducting oxide of indium and tin, a hole-transport layer 7, a photoactive layer 8 obtained by chemical vapor deposition, an electron -transport layer 9, electrode 10.

An example of a model implementation

Powders of lead bromide PbBr ₂ (734 mg) and cesium bromide CsBr (424 mg) were used as precursors for the synthesis. The powders are mixed with a molar ratio of 1: 1 and ground in a ball mill in 12 cycles of 5 minutes at 400 rpm to achieve a uniform yellow composition with a perovskite structure CsPbBr ₃ and Cs ₂ PbBr ₆ .

A thin film was deposited in a tubular two-zone furnace in a quartz reactor with an inner diameter of 25 mm. A corundum crucible with a mixture of CsBr and PbBr ₂ powders is placed in the reactor in the center of the hot zone of the furnace; a transparent flat substrate is placed horizontally at a distance of 25 cm from the crucible, with successively formed layers 6 of tin-indium oxide and also a hole-transport layer 7 based on oxide nickel according to the diagram shown in FIG. 1, 4. A vacuum of 10 Pa is provided, then an argon flow is injected into the reactor with a flow rate of 3.2 l / h. The furnace is heated at a rate of 15 ° C / min up to 580 ° C, maintained at this temperature for 40 minutes. The zone of the reactor containing the substrates, upon reaching a temperature of 300 ° C in the furnace, is heated to 305 ° C, the temperature is maintained until the end of the process. After 40 minutes of exposure at 580 ° C, heating stops, upon reaching the furnace temperature of 250 ° C (as a result of natural cooling), the maintenance of the dynamic vacuum ceases, argon is pumped into the reactor to atmospheric pressure, then the reactor is depressurized. The perovskite-coated substrates are removed from the reactor. The structure of the obtained material corresponds to the structure of perovskite and is confirmed by the diffraction pattern shown in figure 2, as well as by the photoluminescence spectrum shown in figure 3. Layers 8 of an electron transport material and a metal electrode are deposited on the resulting material, for the implementation of a light-emitting diode with a photoactive perovskite layer obtained by the method deposition from the gas phase. The resulting device was connected to a DC power supply and showed visible electroluminescence at 2.8 V while increasing the voltage sequentially from 0 to 5 V.

The technological advantage of the process is a one-stage scalable synthesis without the use of liquid processes during the formation of a photoactive perovskite layer with a thickness of 8 nm to 8000 nm, a photoluminescence peak in the visible spectral range from 400 to 780 nm with a quantum yield of 2 to 40%. This technology is adapted for implementation in the production line of solar cells, displays, photodetectors.

Claims (1)

A method of chemical deposition of continuous films with a perovskite structure with the structural formula APbX ₃ for the production of photovoltaic devices, LEDs and photodetectors, where A is a cation in the form of CH ₃ NH ₃ ⁺ , or (NH ₂ ) ₂ CH ⁺ , or C (NH ₂ ) ₃ ⁺ , or Cs ⁺ , or mixtures thereof, X is an anion in the form of Cl ^- , or Br ^- , or I ^- , or a mixture thereof, from the gas phase, which consists in grinding the synthesis components AX and PbX ₂ in a molar ratio ranging from 1 : 4 to 1: 1 in a ball mill in the mode of 12 cycles of 5 min at 400 rpm until the formation of a stoichiometric compound, the subsequent charging of the grinding products in the heating zone and evaporation of the synthesis components, placing a flat substrate in the heating zone and precipitation of synthesis products, ensuring pressure of 10 Pa in the reaction volume and the flow of the transport gas in the direction from the heating zone of the reaction components to the zone of precipitation of the reaction products, an increase in the temperature in the heating zone until the evaporation of the synthesis components, an increase in the temperature in the zone of deposition of reaction products, formation of a photoactive perovskite photoluminescent layer by chemical vapor deposition on a substrate in the zone of deposition of synthesis products at a temperature increased to 305 ° C and maintained until the end of the process.

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