BRPI0713496A2 - process for the production of photoactive layers as well as components comprising these layers - Google Patents

Abstract

PROCESS FOR THE PRODUCTION OF PHOTOACTIVE LAYERS, AS WELL AS COMPONENTS THAT UNDERSTAND THESE LAYERS. The present invention relates to a method for the production of photoactive layers, and to components such as solar cells or photodetectors comprising said layer. The photoactive layer is produced according to the invention by the synthesis of morganic semiconductor particles with microwave irradiation, photoactive layers being formed from said particles in combination with organic semiconductor compounds.

Description

Report of the Invention Patent for "PROCESS FOR THE PRODUCTION OF PHOTO LAYERS, AS AS COMPONENTS UNDERSTANDING THESE LAYERS".

The present invention relates to a process for producing photoactive layers comprising inorganic semiconductor particles as well as organic semiconductor compounds as well as components comprising such layer (s).

Photoactive layers are functionally significant components of photoactive elements, such as solar cells or photodetectors.

The nanoparticles that are integrated in these photoactive layers, in this case, very significantly influence the efficiency of the photoactive elements.

The invention is primarily important in the field of inorganic-organic hybrid solar cells. The design of such hybrid solar cells can be described as follows based on figures 1 to 4:

The photovoltaic cell consists of a transparent carrier 1 which preferably consists of glass or a polymer such as polyethylene terephthalate (PET). A transparent electrode layer 2 consisting of a conductive oxide, for example indium tin oxide (ITO), a transparent conductive polymer or other transparent material with high conductivity is applied to the carrier. Such an electrode layer generally has a comparatively rough surface structure, so it is optionally covered with a smoothing layer 3 consisting of a polymer which is electrically conductive by doping, generally PEDOT: PSS ( polyethylenedioxythiophene: polystyrene sulfonate). A photoactive layer 4 consisting of semiconductor particles and an organic semiconductor matrix with a layer thickness, depending on the application process, for example from 100 nm to several micrometers, can be applied directly to the smoothing layer 3.

Regarding the photoactive layer in such solar cells, as described in the literature - see, for example, C.J. Brabec, N.S. Sariciftci, J.C. Hummelen, Adv. Funct. Mater. 11 (2001) 15-26) - two concepts are available, namely the concept of mass heterojunction, see figure 1: diagrammatic representation, as well as figure 3: diagram without PEDOT: PSS (polyethylenedioxythiophene.sulfonate). polystyrene) and the concept of bilayer heterojunction, see figure 2: diagram as well as figure 4: Diagram without PEDOT: PSS. In the case of the concept of mass heterojunction, the photoactive layer consists of a mixture of an electroactive polymer and semiconductor particles of low molecular weight electroactive molecules and semiconductor particles 4. In the concept of bilayer heterojunction, the photoactive layer It consists of an electroactive organic layer 6 and an underlying inorganic semiconductor layer 7. In principle, the two systems can also be combined with one another.

The production of hybrid solar cells is performed with the application of metallic electrodes. Frequently used electrode materials are silver, aluminum, gold or a combination of calcium and aluminum, calcium and gold, magnesium and gold.

The function of semiconductor particles in hybrid solar cells is described in the literature, see E. Arici, S. Sariciftci, D. Meissner, Adv. Funct. Mater. 13 (2003) 165-171) in the CulnS2 Nanoparticle Example- Here, nanoparticles increase the efficiency of polymeric solar cells by preventing recombination of the charge carriers generated by carrying the negative charge carrier transport to the electrodes.

The use of additional semiconductor particles is known from the literature. Some are mentioned below by way of example: W. U. Huynh, J. J. Dittmer, and A. P. Alivisates describe in Science 2002, 295, 2425 the use of CdSe nanoparticles; N. C. Greenham, X. Peng, and A. P. Alivisates describe in Physical Review B 1996, 54, 17628 the use of CdS nanoparticles; W.J.E. Beek, Μ. M. Wienk, and R. A. J. Janssen describe in Advanced Materials 2004, 16, 1009 the use of ZnO nanoparticles; and Κ. M. Coakley, Υ. X. Liu, C. Goh and M. D. McGehee describe in Mrs Bulletin 2005, 30, 37 the use of TiO2 nanoparticles.

Inorganic semiconductor nanoparticles that are required for production can be produced by a variety of methods. Such methods are, for example, colloidal synthesis, solvothermal synthesis (high pressure autoclave synthesis), gas phase reactions (chemical vapor synthesis), as well as electrochemical production methods.

Many known processes for producing semiconductor nanoparticles are, however, relatively expensive from a processing standpoint. On the other hand, for many colloidal syntheses and gas phase reactions, complex precursor materials are generally used and, on the other hand, solvothermal syntheses are time consuming and, based on the high pressure required, require reactors that are especially designed for this purpose. Here the invention is intended to correct this.

According to the invention, a process of the above type is proposed, which is characterized by the fact that inorganic semiconducting particles are synthesized under microwave radiation, from which photoactive layers are formed together with semi- organic conductors.

If photoactive layers are used in solar cells according to the principle of mass heterojunction, the possibility exists to produce all the necessary material for the photoactive layer (non-composite) material under microwave irradiation by the semiconductor particles being produced. under microwave irradiation directly in a solution of an electroactive polymer or low molecular weight electroactive molecules. This polymer-semiconductor particle solution can then be used directly without an additional process step of the active layer of a hybrid solar cell. Further, it is advantageous that the concentration ratios between a polymer and a nanoparticle portion in the nanocomposite material are varied as desired.

Advantageous configurations are revealed according to the overlap.

The invention also relates to components such as solar cells or photodetectors comprising the photoactive layers which are produced according to the invention. The advantages of the process according to the invention are based on significant simplification in the production of semiconductor particles, particularly semiconductor particles having a diameter of only a few nanometers. In this regard, this is a very simple and economical process, since by the use of microwave radiation, the reaction time can be greatly reduced and economical starting compounds can also be used. In many cases, the synthesis of nanoparticles can be performed starting from the respective elements and from simple metal salts. In contrast, metal complexes with organic binders that are expensive and difficult to handle have to be used for many colloidal nanoparticle syntheses. The synthesis of Cd-containing nanoparticles such as CdS, CdSe and CdTe1 are an example of nanoparticle syntheses starting from organometallic precursor compounds, see: C. B. Murray, D. J. Norris, M. G. Bawendi1 J. Am. Chem. Sound. 115 (1993) 8706.

Semiconductor nanoparticles which are produced by microwave supported synthesis and which are present in the photoactive layers according to the invention have been exposed to microwave radiation at least once before or during the production of the layer. In this case, microwave radiation is characterized by a wavelength of 1 m to 1 mm and a frequency range between 0.3 GHz and 300 GHz.

Semiconductor nanoparticles produced by microwave supported synthesis may be present in the photoactive layer as individual particles, as individual particle agglomerates or as percolated individual particle networks or particle agglomerates.

Semiconductor particles can be produced by organic supported microwave synthesis methods, but also without fillers. Surfactants that act as stabilizers for nanoparticles are referred to as fillers. The great advantage of unfilled syntheses is that particle surfaces are in most cases not wrapped with insulating organic layers, whereby satisfactory results can be achieved by using the photoactive layer in a solar cell.

Calcogenidic particles are important and advantageous semiconductor particles for the production of hybrid solar cells. The process for producing hybrid solar cells that is described herein thus primarily relates to the use of calcogenic semiconductor particles of the type: ABX2, AB5X9, AB5X8, CX, D2X3 and the like, whereby: A = Cu, Ag, Zn, Cd; B = In, Ga, Al; C = Cu, Ag, Zn, Cd, Pb, Hg, I, Tm, Yb; D = Al, In, Ga, TI, Y, La, B; and X = S, If, Te.

As additional components in the photoactive layer, organic semiconductor polymers according to the invention are used. These refer to polymers having a conjugated π electron system such as trans-polyacetylene, polypyrrole, polythiophene, polyaniline, poly-p-phenyleninylene, poly-p-phenylene, polyfluorene, polyaromatic amines, poly (thienylene vinylene) and its derivatives.

The invention is explained in more detail below based on the embodiments and based on figures 1 to 10.

Here, Figure 1 presents the design diagram of a hybrid solar cell according to the principle of mass heterojunction,

Figure 2 shows the design diagram of a hybrid solar cell according to the bilayer heterojunction principle.

Figure 3 shows the design diagram of a hybrid solar cell according to mass heterojunction without PEDOT: PSS,

Figure 4 shows the design diagram of a hybrid solar cell according to the PEDOT: PSS bilayer heterojunction principle,

Figure 5 shows the current / voltage characteristic of a mass heterojunction solar cell with MEH-PPV (poly [2-methoxy-5- (2-ethyloxy) -p-phenylvinylene]) and CuInS2 nanoparticles from a mi supported synthesis - dichloromethane chromes,

Figure 6 shows the current / voltage characteristic of a mass heterojunction solar cell with P3HT (poly-3-hexylphifene) and ZnS nanoparticles of a toluene / pyridine microwave supported synthesis.

Figure 7 shows the current / voltage characteristic of a mass heterojunction solar cell with MEH-PPV and CulnS2 nanoparticles from a microwave supported synthesis of ethylenediamine.

Figure 8 shows the current / voltage characteristic of a P3HT bilayer heterojunction solar cell and CulnS2 nanoparticles from a microwave supported synthesis of triethylene glycol / pyridine,

Figure 9 shows the current / voltage characteristic of a mass heterojunction solar cell with MEH-PPV and CulnS2 nanoparticles from a triethylene glycol / pyridine microwave supported synthesis, and

Figure 10 shows the XRD (X-ray structural analysis) analysis of ZnS nanoparticles produced according to Example 2.

Example 1

Production of hybrid solar cells with Cu-lnS2 nanoparticles produced under microwave irradiation in dichloromethane:

Synthesis is carried out with Cul (1 equivalent), InCl 3 (1 equivalent) and thioacetamide (2.2 equivalent) reagents in dichloromethane as solvent. Reaction parameters are: 180 ° C, 38 bar, as well as microwave radiation for 15 minutes. Reaction time can be kept very short by adjusting pressure, temperature and duration as well as microwave radiation intensity.

The fine black particles and dust that are obtained are removed by centrifugation of the reaction solution, washed and mixed with a MEH-PPV solution. This suspension can now be used as a photoactive layer in a hybrid solar cell.

For example, hybrid solar cells according to the diagram of Figures 1 to 4 may be produced from synthesized photoactive layers. As a result, hybrid solar cells according to the invention can both be implemented according to the concept of mass heterojunction and also according to the concept of bilayer heterojunction.

For solar cell production, a portion of the ITO (indium tin oxide) layer is removed by blasting with Zn / HCl and ITO flakes, ie glass carriers coated with ITO: 15 mm χ 15 mm χ 1, 1 mm are poured into an isopropanol (pa) beaker and purified for 15 minutes in an ultrasonic bath at 60 ° C.

Next, a PEDOT: PSS layer and the photoactive layer that is produced according to the invention are applied.

Up to this point, the photoactive layer can be applied from a spin-coating solution or suspension. In the suspension that is used, a polymer concentration (MEH-PPV) of 3 mg / mL and a ratio of polymer to CuInS2 nanoparticles from 1 to 7 (parts by weight) are present.

The photoactive layer is then dried at 150 ° C in an inert gas atmosphere. Finally, metal electrodes, for example aluminum, are applied.

In Figure 5, the current / voltage characteristic of the solar cell produced according to Example 1 is demonstrated. This indicates a clear photo effect, whereby the measured photoelectric current is 5.7 μΑ / cm2, and the measured photoelectric voltage is 200 mV.

Example 2

Production of hybrid solar cells, whose photoactive layer consists of a nanocomposite material made of P3HT (poly-3-hexylthiophene) and ZnS nanoparticles, which were produced directly under microwave radiation:

According to this example, ZnS nanoparticles are produced under microwave irradiation directly in a solution consisting of an organic semiconductor polymer. For this purpose, anhydrous zinc acetate (1 equivalent) and thioacetamide (1.2 equivalent) were dissolved in a mixture of toluene and pyridine, and P3HT is suspended in this solution as a semiconductor polymer. The reaction is carried out in a synthesis microwave oven. Thus, the polymer is completely dissolved without ZnS nanoparticles being formed before the end of the reaction; The reaction mixture is first maintained under microwave radiation for 20 minutes at 80 ° C, then for 10 minutes at 120 ° C and brought under microwave radiation for 30 minutes at 180 ° C. Through this microwave-supported synthesis method, the suspension for application of the nano-composite layer is produced in one step as a photoactive layer in the solar cell. The XRD analysis of the semiconductor particles produced in the polymer solution (see figure 10) clearly shows - based on the two wide peaks 27 ° to 34 ° and 48 ° to 55 ° - that this is nanocrystalline ZnS. Primer crystallite sizes of approximately 3 to 4 nm were found by Debye-Scherrer analysis.

Using this photoactive layer produced according to the invention, the solar cell was produced analogously to Example 1.

The current / voltage characteristics of this solar cell in the dark and lighting conditions are shown in Figure 6. The solar cell shows an excellent diode characteristic, a low dark current, a 54 μΑ / cm2 photoelectric current and a photoelectric voltage. of 660 mV.

Example 3

Production of Cu-lnS2 nanoparticle hybrid solar cells from a microwave synthesis on ethylenediamine as a solvent and as a stabilizer for the semiconductor nanoparticles that are produced:

CulnS2 particles were produced directly from Cu (1 equivalent), In (1 equivalent) and S (2 equivalent) elements. As a solvent and simultaneously as a filler, anhydrous ethylenediamine was used. The reaction was carried out in a Teflon liner at 160 ° C for 60 minutes under microwave radiation.

Fine black powder particles were obtained which were removed by centrifugation of the reaction solution, washed and mixed with a MEH-PPV solution. Such a suspension with a polymer concentration of 3 mg / mL, a polymer to nanoparticle ratio of 1 to 5 (parts by weight) can now be used as a photoactive layer for hybrid solar cells.

The primary design of this hybrid solar cell is analogous to Example 1. In Figure 7, the current / voltage characteristic of the solar cell is demonstrated. The latter shows a clear photo effect, whereby the measured photoelectric current is 3.6 μΑ / cm2, and the measured photoelectric voltage is 290 mV.

Example 4

Production of Cu-InS2 nanoparticle hybrid solar cells:

For the production of CuInS2 nanoparticles, CuCl (98 mg, 1 mmol) is weighed in a Teflon liner (microwave reaction flask) and 30 mL of triethylene glycol as well as 20 mL of pyridine are added. The mixture is then heated for 15 minutes in the 180 ° C synthesis microwave. In this case, CuCI is completely dissolved, and a green solution is produced.

After cooling, indium metal powder (114 mg, 1 mmol) and sublimated sulfur (64 mg, 2 mmol) are weighed in a Teflon liner.

The reaction is carried out for 40 minutes or 60 minutes at 180 ° C under microwave irradiation. During the reaction a slight excess pressure is produced in the containers.

Black fine dust particles, which temporarily form a stable suspension in a red reaction mixture, are produced.

These particles are removed by centrifugation, washed three times with ethanol and dried overnight at 60 ° C in a drying oven. The particles are then resuspended in toluene and sonicated for 20 minutes for better distribution.

The synthesis may be modified by the addition of various solvents, for example pyridine or tetraethylene glycol, to the standard triethylene glycol solvent.

In addition, the synthesis of semiconducting nanoparticles can be altered by the addition of fillers such as, for example, TPP (triphenylphosphite), TOP (trioctyphosphine) or hexadecylamine.

For the production of solar cells, poly-3-hexylthiophene (P3HT), poly [2-methoxy-5- (2-ethylexyloxy) -p-phenylvinylene] (MEH-PPV) and poly [2-methoxy-5- (3 , 7-Dimethyloctyloxy) -p-phenylvinylene] (MDMO-PPV) are used in combination with semiconductor nanoparticles as semiconductor polymers.

The bilayer heterojunction solar cell is produced with the following parameters:

Polymer solution for active layer: P3HT: 3 mg / mL in toluene.

Nanoparticle suspension for active layer: 15 mg / mL in ethanol.

The mass heterojunction solar cell is produced with the following parameters:

Solution for active layer:

MEH-PPV: Nanoparticles = about 40:60 m% (polymer concentration: about 3 mg / mL in toluene).

As examples, current / voltage characteristics of a bilayer heterojunction solar cell are shown in Figure 8, and current / voltage characteristics of a mass heterojunction solar cell are shown in Figure 9. The parameters describing the cells Solar can also be found in the figures. The bilayer heterojunction solar cell produces a photoelectric current of 4.5 μΑ / cm2 and a photoelectric voltage of 270 mV. The hybrid solar cell according to the mass heterojunction principle has a very small dark current, a good diode characteristic and produces a photoelectric current of 21 μΑ / cm2 and a photoelectric voltage of 755 mV.

In addition to the examples cited, further tests were made that led to the following findings:

Semiconductor organic compounds, for example phthalocyanines or perylenes or oligomers of semiconductor polymers, rather than semiconductor polymers, were used in hybrid solar cells. The solar cells that were produced provided similar photoelectric currents and photoelectric voltages for the solar cells described in Examples 1 to 4.

Furthermore, it has been found in other experiments that in addition to Cu, In and / or Zn elements, Ag, Cd, Ga, Al, Pb, Hg, Se and / or Te elements can also be used.

In summary, it can be established that the process according to the invention is uncomplicated and energy efficient with respect to processing, since by the use of microwave radiation, the reaction time can be greatly shortened. In addition, with this process, the polymer / semiconductor particle suspension that is required for application of a photoactive nanocomposite layer can be produced in one step by producing the semiconductor particles in the polymer solution under microwave irradiation. This has the additional advantage that semiconductor particles are especially evenly distributed in the electroactive polymer.

With this process, photoactive layers, whose applications in the case of photoactive elements, such as solar cells, result in satisfactory degrees of efficiency, can be produced.

Claims (18)

Process for the production of photoactive layers comprising inorganic semiconductor particles and organic semiconductor compounds, characterized by the fact that inorganic semiconductor particles are synthesized under microwave irradiation, from which photoactive layers are formed together with organic semiconductor compounds. A process according to Claim 1, wherein the synthesis of inorganic semiconductor particles and the formation of the photoactive layer is performed in two steps. A process according to Claim 1, wherein the synthesis of inorganic semiconductor particles and the formation of the photoactive layer is performed in one step. Process according to Claim 3, wherein the production of the inorganic semiconductor particles is carried out directly in a solution or suspension of the organic semiconductor compound under microwave irradiation and the suspension thus obtained is further processed directly in a layer. photoactive. A process according to one of Claims 1 to 4, wherein the inorganic semiconductor particles have a diameter of 1 nm to 1 μm, preferably from 2 nm to 100 nm. Process according to one of Claims 1 to 5, wherein the inorganic semiconductor particles are produced from metallic calcogenides. A process according to claim 6 wherein as metal calcogenides those of the type ABX2, AB5Xg, AB5X8, CX1 D2X3 and the like are selected from: A = Cu, Ag, Zn, Cd; B = In, Ga, Al; C = Cu, Ag, Zn, Cd, Pb, Hg, I, Tm, Yb; D = Al, In, Ga, TI, Y, La, B; and X = S, If, Te. Process according to one of Claims 1 to 5, wherein the inorganic semiconductor particles are produced from the respective elements of the periodic table. Process according to one of Claims 1 to 5, wherein the inorganic semiconductor particles are produced from metal salts and / or metal compounds and a calcogenide compound. A process according to one of Claims 1 to 9, wherein as organic semiconductor compounds, semiconductor polymers and / or semiconductor oligomers are used. A process according to claim 10, wherein the semiconductor polymers and / or semiconductor oligomers are selected from the group trans-polyacetylene, polypyrrole, polythiophene, polyaniline, poly-p-phenylenovinylene, poly-p-phenylene, polyfluorene. polyaromatic amines, poly (thienylene vinylene) and / or derivatives thereof. Process according to one of Claims 1 to 9, wherein as organic semiconductor compounds, phthalocyanines and / or perylenes are used. Process according to one of Claims 1 to 12, wherein the production of inorganic semiconductor particles is carried out with the aid of surfactants (fillers). Process according to one of Claims 1 to 13, wherein the inorganic semiconductor particles are present in the form of agglomerates. Process according to one of Claims 1 to 13, wherein the inorganic semiconductor particles are present in the form of percolated particulate networks. Process according to one of Claims 1 to 15, wherein the microwave radiation that is used is in a wavelength range of 1 m to 1 mm and a frequency range between 0.3 GHz and 300 µm. GHz. A component comprising a photoactive layer which is produced according to one of Claims 1 to 16. A component according to Claim 17 wherein the photoactive element is a hybrid solar cell. Component according to Claim 17, wherein the photoactive element is a photodetector.