Dye comprising a chromophore to which an acyloin group is attached

Abstract

The present invention related to a dye comprising a chromophore to which an acyloin group as anchoring group is attached, to a method of synthesis of such dye, to an electronic device comprising such dye and to the use of such dye.

Claims

1. An electric device, comprising a dye and a photoactive semiconductor porous material, wherein the dye comprising a chromophore to which an acyloin group is attached, and represented by formula (2e) ##STR00027## wherein said chromophore absorbs electromagnetic radiation in a range from 300-1200 nm and is ##STR00028## wherein X is C, Z is one or more moieties which, at each occurrence, is independently selected from the group consisting of H, a cyclic alkyl, an acyclic alkyl, a straight or branched chain moiety of formula (CH.sub.2).sub.n1R, [(CRCR).sub.n1(CH.sub.2).sub.n2].sub.pR, [(CC).sub.n1(CH.sub.2).sub.n2].sub.pR, [(CH.sub.2).sub.n1X.sub.n2].sub.pR, a halogen, a substituted phenyl, an unsubstituted phenyl, a substituted biphenyl, an unsubstituted biphenyl, and an unsubstituted heteroaryl, n32 1, n1 and n2=0-12 and p=0-6, wherein X is CR.sub.2, O, S or NR, wherein R is selected from the group consisting of H, a straight or branched alkyl chain of formula C.sub.nH.sub.2n+1, COOR.sup.1, OR.sup.1, SR.sup.1, NR.sup.1.sub.2, F, Cl, Br, I, CN, and CF.sub.3; wherein R.sup.1 is H, a straight or branched alkyl chain of formula C.sub.nH.sub.2n+1, a substituted or non-substituted phenyl or biphenyl or heteroaryl, and n=1-12.

Description

(1) Furthermore, reference is made to the figures, wherein

(2) FIG. 1 shows a synthesis scheme of one example dye in accordance with the present invention being represented by general formula 2e, E being Cl or an alkoxy group, preferably ethoxy, propoxy, iso-propoxy or butoxy, X being as defined above, chromophore being as defined above,

(3) FIG. 2 shows a synthesis scheme of one example dye in accordance with the present invention being represented by general formula 2h, E, Y, X, n.sub.1, n.sub.2, p, chromophore being as defined above, Hal.sup. being I.sup., Cl.sup., Br.sup., NCS.sup. or SCN.sup.,

(4) FIG. 3 shows a synthesis scheme of one example dye in accordance with the present invention being represented by general formula 5, E, Z, R.sub.11-R.sub.13, X being as defined above,

(5) FIG. 4 shows a synthesis scheme of one example dye in accordance with the present invention being represented by general formula 9, X, Y, Z, R.sub.1 being as defined above,

(6) FIG. 5 shows the molecular structure of some dyes according to present invention,

(7) FIG. 6 shows the synthesis of one example dye in accordance with the present invention being represented by formula 1,

(8) FIG. 7 shows the synthesis of one example dye in accordance with the present invention being represented by formula 2,

(9) FIG. 8 shows the synthesis of one example dye in accordance with the present invention being represented by formula 5,

(10) FIG. 9 shows a photograph of the adsorption of dye in accordance with the present invention being represented by formula 1 on a TiO.sub.2 layer,

(11) FIG. 10 shows a table indicating the performance of a dye sensitized solar cell prepared with a dye in accordance with the present invention being represented by formula 1 by measuring the efficiency of solar cells by means of sulphur lamp,

(12) FIG. 11 shows the incident photon to current efficiency (IPCE) plotted against wavelength for a dye in accordance with the present invention being represented by formula 1,

(13) FIG. 12 shows a table displaying the performance of various dye sensitized solar cells prepared with a dye in accordance with the present invention being represented by formula 1 in mixture with other dyes and in comparison to other sensitizers,

(14) FIG. 13 shows the incident photon to current efficiency of a dye in accordance with the present invention being represented by formula 1, of a dye being represented by formula 14 (FIG. 15) and a mixture of these two dyes, plotted against wavelength,

(15) FIG. 14 shows a table indicating the performance of a dye sensitized solar cell prepared with a dye in accordance with the present invention being represented by formula 1 in comparison with organic dye being represented by formula 16 (FIG. 15), by measuring the efficiency of solar cells by means of sun simulator,

(16) FIG. 15 shows the structure of other sensitizers that were used for comparison and in mixture with dyes according to present invention (sensitizers 14, 15 and 16).

(17) FIG. 16 shows structures 17-26 which are exemplary dyes in accordance with the present invention.

(18) FIG. 17 shows exemplary structures 15, 27-32 of other dyes which can be used together with the dyes in accordance with the present invention.

(19) FIGS. 18-20 show various tables and IPCE curves showing the efficiencies of solar cells, as prepared and described in Examples 11) to 13).

(20) FIG. 21 shows various embodiments of electronic devices in accordance with the present invention wherein energy supply devices, such as solar cell panels, preferably dye sensitized solar cell panels (DSSCs) have been incorporated.

(21) Moreover reference is made to the following examples which are given to illustrate, not to limit the present invention.

Examples

(22) 1) Synthesis of One Embodiment of a Dye in Accordance with the Present Invention, in this Case Dye 1:

(23) FIG. 6 shows the synthesis scheme of dye 1 in accordance with the present invention.

(24) An equimolar amount of 1a and diethylester derivative of squaric acid 1b in ethanol is heated in presence of small amount triethylamine to 70 C. for 4 h. The solvent is removed and the crude product is purified by column chromatography on silica gel with n-hexane/ethylacetate as eluent to yield the pure product 1e.

(25) In next step, to derivative 1c in ethanol aqueous NaOH is added and the mixture stirred for 2 h at 50 C. After cooling, aq. HCl is added and the solvent is removed. The crude product is purified by column chromatography on silica gel with dichloromethane/methanol as eluent.

(26) The dye 1 in accordance with the present invention is isolated as yellow solid.

(27) 2) Synthesis of One Embodiment of a Dye in Accordance with the Present Invention, in this Case Dye 2:

(28) FIG. 7 shows the synthesis scheme of dye 2 in accordance with the present invention.

(29) An equimolar amount of 2a and diethylester derivative of squaric acid 1b in ethanol and in presence of small amount triethylamine is heated to 80 C. for 6 h. The solvent is removed and the crude product is purified by column chromatography on silica gel with n-hexane/ethylacetate as eluent to yield the pure intermediate 2b.

(30) In next step, to 2b in ethanol aqueous NaOH is added and the mixture stirred for 2 h at 50 C. After cooling, aq. HCl is added and the solvent is removed. The crude product is purified by column chromatography on silica gel with dichloromethane/methanol as eluent. The dye 2 in accordance with the present invention is isolated as yellow-orange solid.

(31) 3) Synthesis of One Embodiment of a Dye in Accordance with the Present Invention, in this Case Dye 5:

(32) FIG. 8 shows the synthesis scheme of dye 5 in accordance with the present invention.

(33) An equimolar amount of brominated derivative 5a and diethylester derivative of squaric acid 1b in ethanol and in presence of small amount triethylamine is heated to 80 C. for 6 h. The solvent is removed and the crude product is purified by column chromatography on silica gel with n-hexane/ethylacetate as eluent to yield the pure intermediate 5b.

(34) In a next step, to a mixture of 5b in of toluene/methanol, 1.2 equivalents of thienyl boronic acid, 1 mol % Pd-catalyst, 10 equivalents K.sub.2CO.sub.3 are added. The mixture is allowed to stir at 120 C. for 12h. After cooling the solvent is evaporated. The crude product is purified by column chromatography on silica gel with n-hexane/ethylacetate as eluent to yield pure 5c.

(35) In a subsequent reaction to 5c in ethanol, aqueous NaOH is added and the mixture stirred for 2 h at 50 C. After cooling, aq. HCl is added and the solvent is removed. The crude product is purified by column chromatography on silica gel with dichloromethane/methanol as eluent. The pure dye 5 in accordance with the present invention is isolated as orange solid.

(36) 4) Analytical Data of Dye 1

(37) C18H19NO3 (297.36)

(38) 1H NMR (400 MHz, MeOD): =14.8 (s, 1H, OH), 7.27-7.20 (m, 2H, arH), 6.98-6.92 (m, 2H, arH), 5.70 (s, 1H, CH), 3.95 (t, 2H, NCH2), 1.84-1.75 (m, 2H, CH2-Pr), 1.65 (s, 6H, arCH3), 1.06 (t, 6H, CH3-Pr)

(39) ESI MS m/z=297.8 [M+].

(40) UV/VIS (acetonitrile): max=404 nm.

(41) 5) Effective Adsorption of the Dye on TiO2

(42) FIG. 9 shows a photograph of the adsorption of dye 1 in accordance with the present invention on a TiO.sub.2 layer

(43) For device preparation, the substrate with screen printed nanoporous TiO2 particles is poured and kept in a dye or dyes mixture solution for at least 1 h. The dye molecules having the acyloin group as anchor group are able to adsorb onto the nanoporous layer via self-assembling. The effective adsorption and chemisorption (covalent coupling) of the dyes with acyloin group onto semiconductor surface is proved by the stable color of the substrate even after the substrate was washed with an organic solvent.

(44) 6) General Protocol for Preparing Solar Cells

(45) The DSSCs are assembled as follows: A 30-nm-thick bulk TiO.sub.2 blocking layer is formed on FTO (approx. 100 nm on glass or flexible substrate). A 5-30 m-thick porous layer of TiO.sub.2 semiconductor particles of 0.1882 cm.sup.2 active area multi-printed by screen printing on the blocking layer and sintered at 450 C. for half an hour. Dye molecules are adsorbed to the nonporous particles via self-assembling out of a dye-solution. The dye-solution consists of a single dye or single dye and an additive, such as deoxycholic acid or a mixture of dye in different ratio or a mixture of dye in different ratio and an additive. The porous layer is filled with liquid electrolyte containing I.sup./I.sub.3.sup. as redox couple (15 mM) by drop casting. A reflective platinum back electrode is attached with a distance of 6 m from the porous layer.

(46) 7) Measuring the Efficiency of DSSCs Containing at Least One of the Sensitizer Dye Produced by the Method of the Present Invention

(47) The quality of the cells is evaluated by means of current density (J) and voltage (V) characteristics under illumination with light from a) a sulphur lamp (IKL Celsius, Light Drive 1000) with an intensity of 100 mW cm.sup.2. If not otherwise stated, the results are averages over three cells. b) a sun simulator (AM1.5G YSS-150) with an intensity of 100 mW cm.sup.2.

(48) If not otherwise stated, the results are averages over three cells.

(49) The efficiency of a photovoltaic device is calculated as follows:
=P.sub.out/P.sub.in=FF(J.sub.SCV.sub.OC)/(LA) with FF=V.sub.maxI.sub.max/V.sub.ocI.sub.sc FF=fill factor V.sub.OC=open circuit voltage J.sub.SC=short current density L=intensity of illumination=100 mW/cm.sup.2 A=active area=0.24 cm.sup.2 V.sub.max=voltage at maximum power point J.sub.max=current at maximum power point

(50) An important parameter for judging the performance of a dye as sensitizer in DSSC is the IPCE curve. The IPCE curve reflects the photo-activity of the sensitizer dyes at different wavelengths (IPCE=incident photon to current efficiency).

(51) The respective structure of the dyes is given in FIGS. 5 and 15.

(52) 8) Efficiency of the DSSC by Using Dye 1 as Sensitizer

(53) The performance and the efficiency of DSSCs prepared by method described in 6 and measured by method described in 7a with dye 1 are shown in FIG. 10. FIG. 11 shows the IPCE plotted verses wavelength for sensitizer 1.

(54) The efficiency of the DSSC prepared with sensitizer dye 1 shows high efficiency (>7%). There are only few other organic dyes, such as dye 16, showing such high performance.

(55) However, the superiority of the dyes according to present invention lies not only in the high efficiencies of the DSSCs achieved when using these dyes, but also in their simple preparation (FIGS. 1-4).

(56) The highest achievable IPCE value is 1.0. Sensitizer dye 1 shows an IPCE value of 0.9 in its maximum at ca. 490 nm. That means that the photons absorbed in this region from the sun can be converted to almost 90% to current by injection into conduction band of TiO.sub.2. Such a high value is rarely achieved and only with few dyes, such as the Ruthenium based standard red dye.

(57) 9) Efficiency of M-DSSC Containing a Mixture of Dye 1 and the Organic Dye 14, and a Mixture of Dye 1 and Standard Black Dye 15

(58) The solar cells were prepared by method described in Example 6 and measured according to Example 7a. For comparison also DSSCs prepared with the respective single sensitizer dye were prepared and measured.

(59) The performance and the efficiency of DSSCs are shown in FIG. 12.

(60) A mixture of the dye in accordance with the present invention, in this case dye 1, with either an organic dye 14 or with a Ruthenium based dye (black dye) 15 yields an increase in short current density and thus, a drastic increase in DSSC efficiency.

(61) FIG. 13 shows the IPCE curve of the individual dyes 1 and 14, and the IPCE curve of a 1:1 mixture of these dyes. The individual dyes are photo-active in different region of the solar spectrum. By using a mixture of the dyes, due to additive behaviour of the IPCE curves, a very broad range solar light can be harvested and converted to current.

(62) 10) Comparing Efficiency of the DSSC Prepared with Dye According to Present Invention, Namely Dye 1, and Another Organic Sensitizer 16 Both Harvesting Light in the Same Range of the Solar Spectrum

(63) The DSSCs were prepared by method described in Example 6 and measured according to Example 7b.

(64) The DSSC efficiencies are in the same range of 5%. However, when one compares the structure of the dyes, it becomes clear that the dye according to present invention, namely dye 1, is much more easily synthesized than dye 16.

(65) 11) Efficiency of the DSSC by Using Dye 9 and 2 as Sensitizer

(66) The DSSCs were prepared by the method described in Example 6 and by using 25 m TiO.sub.2 layer and measured according to Example 7b. The efficiency and IPCE curve are shown in FIGS. 18a and 18b, respectively.

(67) The IPCE curve reflects the photo-activity of the sensitizer dyes at different wavelengths (IPCE=incident photon to current efficiency). The highest achievable IPCE value is 1.0. Sensitizer dye 1, 9 and 2 show very high, of almost unity, and wide IPCE values.

(68) 12) Performance of Solar Cells Prepared with a Mixture of the Respective Dye and Standard Ruthenium Black Dye 15.

(69) The solar cells were prepared by method described in Example 6 and measured according to Example 7b. For comparison also DSSC prepared with the respective single sensitizer dye 15 was prepared and measured. The efficiency is shown in FIG. 19. As can be seen, the efficiencies by using a mixture of dyes for sensitization are much higher than that using only a single dye as sensitizer.

(70) 13) Performance of Solar Cells Prepared with a Mixture of the Respective Dye and Organic Dye 14.

(71) The solar cells were prepared by method described in Example 6 and measured according to Example 7b. For comparison also DSSC prepared with the respective single sensitizer dye 14 was prepared and measured. a) by using 26 m TiO.sub.2 layers as electrode; the efficiency is shown in FIG. 20a. b) by using 10 m TiO.sub.2 layers as electrode; the efficiency is shown in FIG. 20b.

(72) The efficiencies on thinner layer are slightly lower than on thick TiO2 layer, but, contrary to Ruthenium based sensitizers, still high enough to show the good performance of the dyes. This is attributed to the strong light absorption property of the dyes according to claim 1-12. In both cases, thin or thick TiO2 layers, the efficiency is increased by using a mixture of dyes for sensitization compared to that using a single dye.

(73) The present invention provides for new sensitizer dyes which are useful for being employed in solar cells as well as in photocatalytic applications. They readily adsorb to nanoporous semiconductor layers and are easily manufactured. The use of an acyloin group as anchoring group for chromophores in such applications, to the best knowledge of the present inventors, has never been reported before.

(74) The features of the present invention disclosed in the specification, the claims and/or in the accompanying drawings, may, both separately, and in any combination thereof, be material for realizing the invention in various forms thereof.