ORGANIC-SEMICONDUCTING HYBRID SOLAR CELL

Abstract

The embodiment of this invention lies on experimental evidence of photoconductivity activity of a hybrid solar cell, organic/chalcogenide. The device is made of thin layers of conductive indium-tin-oxide (ITO) on glass with a 100 nm layer of chalcogenide molybdenum di-sulfide (MoS2) and a thin layer of about 50 nm of complex organic compound assembled at room temperature. The device was tested to conventional electrical transport measurements in the regime of 1V to 1V under electromagnetic radiation simulator at 100 mW/cm2. Results indicate solar conversion efficiency of 2.48% and current density of 6.35 mA/cm2.

Claims

1. A organic-semiconducting hybrid solar cell electrically conductive and light sensitive comprising: A first transparent solid laminar substrate; a first transparent conductive metal oxide layer disposed on the first substrate; a layer of chalcogenide semiconductor material, sensitive to light and exhibiting a porous matrix therein, disposed on the first metal oxide layer; a layer of complex organic material, with a light black color composed of graphitic layers of aromatic carbons, allotropes of carbon and/or combination thereof, disposed on the layer of chalcogenide material; a second layer of transparent conductive metal oxide material disposed on the layer of organic material; a second layer of transparent laminar substrate disposed on the second layer of metal oxide material.

2. A organic-semiconducting hybrid solar cell of claim 1, wherein the substrate layers are constituted by amorphous glass or plastic acetate.

3. A organic-semiconducting hybrid solar cell of claim 1, wherein the transparent metal oxide layers are constituted of indium-tin oxide as electrical contacts.

4. A organic-semiconducting hybrid solar cell of claim 1, wherein the chalcogenide layer is constituted by molybdenum disulfide (MoS.sub.2).

5. A organic-semiconducting hybrid solar cell of claim 1, wherein the layer of organic material is a thin layer of about 50 nm and the layer of chalcogenide is about 100 nm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 is a schematic side view of the solar cell of the present invention composed of an amorphous glass substrate (1), an indium-tin-oxide (ITO) layer (2), a layer of molybdenum di-sulfide (MoS.sub.2) (3), a layer of complex organic material compound (4), an indium-tin oxide (ITO) layer (5) and an amorphous glass substrate (6).

[0016] FIG. 2. It is a graph of experimental current-voltage (I-V) data and the performance of solar cells obtained during electromagnetic radiation at 100 mW/cm.sup.2.

[0017] FIG. 3. It is a graph showing the experimental data of electromagnetic radiation power distribution during over solar cell device testing.

DETAILED DESCRIPTION OF THE INVENTION

[0018] In accordance to FIG. 2, the photo-conduction can be measured as described elsewhere by using sun simulator electromagnetic radiation test device station. A total of 100 mW/cm.sup.2 electromagnetic radiation over device surface was administrated, the invented solar dell each tested device was connected using micromanipulators to electrometer model Keithley 6517A and data is collected with Omega scanning card. Data corresponding to power-voltage used during device conversion testing is presented in FIG. 3.

[0019] According to FIG. 1, the layer (1) is a substrate that can be amorphous glass, high temperature plastic acetate or any other solid laminar material, transparent to visible light, able to resist temperatures of up to 300 C. and radiofrequency radiation and exposure to plasma, high energy particles at high vacuum 3 mTorr.

[0020] On the embodiment of this invention in accordance to FIG. 1, In the embodiment of this invention according to FIG. 1, the layer (3) is made of a porous layer chalcogenide of semiconductor MoS.sub.2100nm, is created using radio frequency magnetron sputtering high vacuum system, from commercial 99.9% target material. Chamber was operated at 3 mTorr operating with 13.56 MHz RF power at 275W, to create a film thickness of 100nm, a dwell time of 300 seconds was used during the automated recipe.

[0021] The layer of organic material (4) consists of a solid black paste composed by complex aromatic asphaltene-like molecules, were chemical extracted from Mexican crude oil using recommended D2007-80 ASTM procedure. The black solid was diluted in toluene at concentrations of about 0.1 gr for 10 m L (1:10 ratio) to form a light dark liquid solution. The exact chemical composition characterization of black precipitate is beyond the scopes of the invention.

[0022] The inventors of the present invention aim are to solve above mentioned renewable energy needs and found that using complex aromatic carbon content compounds obtained using D2007-80 ASTM norm is possible to produce a reliable device for solar energy conversion. Then, the present invention is considered as completed. Conforming to the present invention, we are providing evidence of a hybrid or dye-sensitized solar cell device composed by a layer of semiconducting chalcogenide material (3) and a layer organic (4) composed by complex aromatic carbon graphitic-like compound. Which are placed in contact using conductive metal oxide transparent substrates, wherein the electrolyte is retained in a crosslinked polymer compound.

[0023] According to the invention, as presented here, a thin layer of indium-tinoxide (ITO) (2), as conductive transparent materials for electrical contacts, is placed on a transparent glass substrate (1) when the solar cell is manufactured, and on this layer of indium-tin-oxide (2) is placed a layer of porous chalcogenide semiconductor material (3) with chemical formula MoS.sub.2, known as molybdenum di-sulfide and deposited by a high-vacuum radiofrequency technique, a layer of complex organic material (4) obtained according to the standard norm D2007-80 ASTM and mixed in organic toluene solvent to conform a liquid solution-paste with a light black aspect color and deposit by spin coating over second amorphous glass substrate (6) prepared with a second layer of indium-tin-oxide (ITO) (5) at room temperature and baked at 80 C. for 1 minute to release any solvent residue.

[0024] Both substrates (1 and 6) are sandwiched together, the layer of complex organic material (4) and the layer of chalcogenide semiconductor material (3) remaining in direct contact forming a cell arrangement and having sides of each layer exposed with a Indium-tin-oxide (ITO) layer (2 and 5) as contact parts for electrical conductivity tests.

[0025] The solar cells were exposed to electromagnetic radiation (100 mW/cm.sup.2) in a solar simulator laboratory station for device performance and conversion efficiency, obtaining a value of 2.4% and a current density of 6.35 (mA/cm.sup.2).

[0026] All obtained data values are presented in FIGS. 2 and 3 and compared with results as presented in the literature.

[0027] The following table shows the increase in efficiency when using the specific combination of the layers according to the solar cell of the present invention.

TABLE-US-00001 TABLE 1 Current density, voltage, solar efficiency and fill factor on hybrid organic-semiconducting solar cell device for comparison other data is presented. Material J.sub.sc(mA/cm.sup.2) V.sub.oc (V) Efficiency (%) FF Au/MoS.sub.2 5.37 0.59 1.8 0.55 MoS.sub.2/PTB7 1.98 0.21 0.1 0.21 Asphaltene/CoMoS.sub.2 0.49 0.41 0.1 0.25 MoS.sub.2/p-Si 3.2 0.14 1.3 0.42 Organic/MoS.sub.2 6.35 0.46 2.48 0.84

[0028] The main parameters to obtain the performance of solar cells are the short-circuit current I.sub.sc, the open-circuit voltage V.sub.oc, and the fill factor FF. These parameters are determined from the dark and illuminated current-voltage (I-V) characteristic, in the following paragraphs are described the main equations and procedures to obtain these parameters for the devices fabricated with Organic/MoS.sub.2 solar cell structure, in addition a comparison with the state of the art is presented.

[0029] The short-circuit current ('.sub.sc) is the current that flows through the external circuit when the electrodes of the solar cell are short circuited. The short-circuit current of a solar cell depends on the photon flux density incident on the solar cell, which is determined by the spectrum of the incident light. For a standard solar cell measurement, the standard is the AM1.5 spectrum. The I.sub.sc=(J.sub.sc/Area) depends on the area of the solar cell, in addition, the maximum current that the solar cell can deliver strongly depends on the optical properties of the solar cell, such as absorption in the absorber layer and reflection.

[0030] Open-circuit voltage (V.sub.oc): The open-circuit voltage is the voltage at which no current flows through the external circuit. It is the maximum voltage that a solar cell can deliver. V.sub.oc corresponds to the forward bias voltage, at which the dark current compensates the photocurrent. Voc depends on the photo-generated current density and can be calculated from Eq.

[00001]$V_{\mathrm{OC}}=\frac{\mathrm{nkT}}{q}.Math.\ln \left(\frac{I_L}{I_O}+1\right)$

[0031] Where I.sub.o is the saturation-current of the p-n junction in dark, I.sub.L is the light generated current, n is an ideality factor, k is Boltzmann's constant (k=1.3810.sup.23 J/K). kT is the thermal energy, at 300 K it is 0.0258 eV, q is the electron charge.

[0032] Fill factor: The power from the solar cell is zero. The fill factor (FF) is the parameter which, in conjunction with V.sub.oc and I.sub.sc, determines the maximum power from a solar cell. The FF is defined as the ratio of the maximum power (I.sub.mp, V.sub.mp) from the solar cell to the product of V.sub.oc and I.sub.sc, as is show in following eq. Graphically, the FF is a measure of the squareness of the solar cell and is also the area of the largest rectangle which will fit in the I-V curve, as is shown in FIG. 2.

[00002]$\mathrm{FF}=\frac{I_{m.Math.p}{v}_{m.Math.p}}{I_{s.Math.c}{v}_{o.Math.c}}$

[0033] Determination of FF using P.sub.max area: The current voltage characteristic (I-V curve) of a solar cell is the superposition of the I-V curve in the dark with the current generated by light. Illumination shifts the I-V curve down into the fourth quadrant where power can be extracted from the diode. The efficiency of a solar cell () is determined as the fraction of incident power which is converted to electricity and the maximum power is given by the following equations: The sample was tested using a standard AM1.5 G simulated solar spectrum at 100 mW/cm.sup.2

[00003]$=\frac{v_{o.Math.c}{I}_{s.Math.c}F.Math.F}{P_{i.Math.n}}.Math..Math.P_{m.Math..Math.\mathrm{ax}}=V_{o.Math.c}.Math.I_{s.Math.c}.Math.\mathrm{FF}$

[0034] where V.sub.oc is the open-circuit voltage, I.sub.sc is the short-circuit current; FF is the fill factor and is the efficiency, respectively.

[0035] The measurements were done using an electrometer 6517A Keithley and a solar cell simulator. The samples were measured using a solar simulator (Newport) under steady illumination AM1.5 spectral filter, and the light sensor current (Newport Oriel digital exposure controller, Model 68945) to provide 1 Sun (100 mW/cm.sup.2). The I-V curves of all samples were measured using an electrometer with bias voltage from 1 to 1 Volt and using the tips of micro-manipulators making a contact to the area of the thin films without any metal-contact deposition. The solar simulator was turned on at least 30 min prior to measurement and calibrated to 1 Sun. Before each measurement the cells were kept at illumination and under dark conditions.

[0036] For these measurements and linear behavior was observed in all the samples, a good ohmic contact without any metal-contact is presented, the electrical resistance of the material is around 4 Kohms. All samples were measured under dark and light conditions using an instrument called semiconductor parameter analyzer model 4200-SCS from Keithley. The Model 4200- SCS is an integrated system that includes instruments for making DC and ultra-fast I-V. These I-V characteristics were measured using the Source-Measure Units (SMUs), which can source and measure both current and voltage. Because these SMUs have four-quadrant source capability, they can sink the cell current as a function of the applied voltage, the DC range for this instrument is from 1A to 1A. The range of voltage was from 6V to 6 volts and the measurements were performed under dark conditions and after that the samples were radiated with a visible light (lamp of 100 W) and measured again with the same equipment, the tips of the micromanipulator were put over the samples without any metal contact.

[0037] The above mentioned and other specific details of the present invention can become further superficial from a detailed description given elsewhere. Though, it would be understood that complete description of device performance and examples, as indicated or referred embodiments of the invention are provided by meaning of data sets and illustrations; thus, a diverse modification within the core of the present invention are or can be clear solely to skilled individuals with high-background knowledge of the description.