KR101091707B1 - green-emitting spectrum converters and poly crystalline silicon solar cell elements coated with the converters - Google Patents

Abstract

The present invention relates to a green light emission spectrum converter and a polycrystalline silicon solar cell device coated with the green light emission spectrum converter. The present invention provides a polycrystalline silicon solar cell device coated on a substrate to increase efficiency.

The composition of the present invention is 0.25 to 10 wt% green light emitting phosphor, 0.1 to 1 wt% silicon particles, and the rest are epoxy (-COC-) group or silicon-organic compound (-CO-Si-C-) group polymer. It is characterized by a green emission spectrum converter which is composed of 100 wt% and a polycrystalline silicon solar cell device coated with the green emission spectrum converter.

Optical Converter, Polycrystalline Silicon, Solar Cell Element, Green Light Emitting

Description

Green-emitting spectrum converters and poly crystalline silicon solar cell elements coated with the converters}

The present invention relates to a green light emission spectrum converter and a polycrystalline silicon solar cell device coated with the green light emission spectrum converter. In detail, a green light emission spectrum converter is coated on a front surface of a polycrystalline silicon solar cell device having low efficiency, and thus an open voltage and a short circuit. It relates to a technique for increasing efficiency by increasing electrical parameters such as current density and fill factor.

The solar energy sector has become a hot issue in the world of renewable energy, especially in the world. The United States, Germany, Spain, Australia and Korea have long-term programs on solar energy to increase the proportion of renewable energy resources.

The solar cell element is made of elemental silicon, but the production cost is high, but the quality of the solar cell element is often low [Ref. 1].

The R & D period in the solar energy sector is over 50 years and the most successful application is to supply energy to spacecraft in stationary orbits. Space solar cell device provides up to 200W per 1m ² of the active solar cell element.

As mentioned above, the main photovoltaic space solar cell device is made of single crystal silicon, and the solar power is 1000 W / m ² in space, the device provides 200 W / m ² , the efficiency is 20%. .

There is also a small share but a solar cell device consisting of hetero-junction IIIA-VB, whose efficiency is more than 40%, as reported by J. Alferov's data. However, these types of devices are too expensive to be practical and their use is limited.

However, the field of application of single crystal silicon solar cell devices is very wide. There are up to $ 10,000 kW solar power plants per 1 kW _p nominal capacity. The most expensive portion of single crystal solar cell devices is the cost of single crystal silicon and wafer production technology.

Due to the problems of the single crystal silicon device as described above, a lot of research efforts are directed to the field of developing an efficient solar cell device using polycrystalline silicon. These polycrystalline silicon semiconductor materials are made of high purity raw material silicon having a control component of 1 × 10 ^-6 % or less.

Non-monocrystalline polycrystalline silicon can be used as an ingot and the device cell has a crystal orientation. The production of polycrystalline silicon cells does not require much energy consumption since there is no single crystal growth.

Therefore, polycrystalline ingots of ultra-high purity silicon are typically 35-40% cheaper than single crystal ingots. Because of the cost of raw materials, many laboratories and plants produce photovoltaic cells based on cheaper polycrystalline silicon.

However, the efficiency of mass-produced polycrystalline devices is about 10-11% and only a few special samples of polycrystalline optoelectronic devices show about 13-14%.

Looking at the causes of the low-energy conversion of the polycrystalline silicon solar cell device, because the first wafer thickness of the solar cell is 120 ~ 260 μm. The back side of the wafer has a solid electrode while the p-n junction is located on the front side, which allows the electrons and holes, the main electric carriers, to be separated and stored separately in the semiconductor. The depth of this junction is usually close to about 30-40 μm. Elemental silicon has a high reflectivity of n ≒ 3 so that sunlight can be reflected from the wafer.

In order to avoid light reflection, the front wafer surface is coated with an antireflective component, usually silicon nitride (Si ₃ N ₄ ) which has a strong blue color. This is why the blocking of the polycrystalline non-oriented structure on the antireflective wafer is well seen. The spectral region of sunlight reaching the earth's surface is at most λ = 4 to 10 mm at λ = 290 nm, so obviously it is impossible to effectively supply this spectrum to the antireflection layer. In the best case, such a layer can be useful in the narrow spectral region of 450-700 nm and can reduce reflections in this spectral region by up to 38-45%. The first reason for the efficiency loss of polycrystalline silicon solar cell devices is optical and the reflection of light from the wafer is evident.

The second reason for the efficiency loss of polycrystalline silicon is also related to the smaller mobility of the carrier compared to single crystal silicon. The low mobility of the electric carriers in the polycrystalline silicon involves the reduction of key parameters of the single crystal silicon device as follows.

-15-25% open voltage

Short Circuit Current Density in the 20-30% Range

-Filling rate in the range of 22-35%

The loss of electrical parameters mentioned above seems to cause a decrease in efficiency.

There is also another reason for losses in polycrystalline silicon solar cell devices. This is related to the deviation of the maximum solar spectrum (λ _max = 470 nm) and the maximum spectral silicon light response (λ = 940 nm). The maximum spectral photosensitive wavelength of silicon is about twice the maximum spectral wavelength of sunlight. Attempts to resolve this deviation are known and are described in the paper by HJ Hovel [Ref. 4]. He proposed the coating of monocrystalline silicon wafers with light emitting ruby and the efficiency increase of the polycrystalline silicon solar cell device was 1% in absolute value. In this paper, polymer coatings with organic dyes were also tried. However, the effect was negligible and was not applied commercially as a too complex technology. The proposed paper has the following serious disadvantages.

Low efficiency increase

Complex technology of large-scale ruby single crystal production

Due to the difference in thermal expansion and intrinsic spectral reflection, the problem of connection between ruby spectral converter and single crystal silicon device has not been solved.

The proposal for developing a composite film converter for single crystal silicon cell devices [Ref. 5] is more detailed. This device consists of an ethylvinyl acetate film in which inorganic phosphor particles are super-dispersed in the production process. In order to solve the above problem, it is proposed to use aluminum silicate (Y ₃ Al ₅ O ₁₂ : Ce) phosphor having a garnet structure activated by cerium, which provides effective re-luminescence in the region of 460 up to 560 nm. . Patent prototypes according to this proposed technique can increase their intrinsic efficiency by 20-25%. Despite the realization of the technical solution, there is a problem that has not been solved so far, which is also reported in [Ref. 6].

In order to increase the efficiency of polycrystalline silicon solar cell devices, for example to increase 25, 30, 35, 40%, the main problem is to increase the electrical parameters of polycrystalline silicon solar cell devices such as open voltage, short-circuit current density and fill factor. It is a way. Existing solutions involve expensive and short supply single crystal silicon devices.

For reference, Figure 5 shows a photograph of a commercially available polycrystalline silicon solar cell device. The solar cell device has a length of 6 inches. The surface of the wafer is coated with an antireflective layer of Si ₃ N ₄ and because of that layer the wafer has a dark blue reflection. In front of it are two rows of electrodes made of silver paste. Two electrode outlets are connected to the electrode foil using a special welder. The back side of the polycrystalline silicon solar cell device has a solid aluminum electrode.

Referring to the data obtained through the experiment, first, the polycrystalline silicon solar cell device is a slice of the polycrystalline silicon ingot, the blocks of other crystals are clearly observed in the polycrystalline slice of the semiconductor silicon.

Through the naked eye, the stain is observed by reflection. This is related to the reflectance in each separate block element. Such spots do not exist in the block structure of the single crystal silicon solar cell device.

[references]

[Reference 1] T. S. Moss, G. J. Burrell, B. Ellcs, Semiconductor opto-electronis / Butterworths and LTD London, 1973

[Reference 2] M. A. Green, Third Generation photovoltaics: Advanced Solar Energy Conversion / Springer-Verlag, Berlin, 2003

[Reference 3] M. M. Koltun, Optics and metrology of solar cell elements Moscow, Science 1985, 279 pp

[Reference 4] H. J Hovel et al., Solar Energy Materials, Vol. 2 N19 (1979)

[Reference 5] N. P. Soshchin et al., Pat. PK / 20070112051, 2007-11-22

[Reference 6] N. P. Soshchin, Luo WeiHong, B. Paul Tzai, A. Unishkov, The spectral converter for Polysilicon solarcell, Nanotechnology in China, International Conference Mart 2008. P 108-109 /

An object of the present invention for solving the above problems is to provide a green emission spectrum converter to increase the electrical parameters of the polycrystalline silicon solar cell device.

It is another object of the present invention to provide a polycrystalline silicon solar cell device in which a green emission spectrum converter for increasing electrical parameters of the polycrystalline silicon solar cell device is coated on its entire surface to increase efficiency.

The present invention to achieve the object as described above and to solve the conventional drawbacks is 0.25 to 10 wt% green light emitting phosphor, 0.1 to 1 wt% silicon particles, the rest of the epoxy (-COC-) group Or it is achieved by providing a green light emission spectral converter, characterized in that composed of a silicon-organic compound (-CO-Si-C-) group polymer to make up to 100 wt%.

The thickness of the green light emission spectrum converter is 50 ~ 250μm coated and the size of the green light emitting phosphor and nano silicon particles dispersed in the converter is characterized in that up to 1/500 ~ 1/1000 of the converter thickness.

The green light emission spectrum converter strongly absorbs short wavelength solar light in the 300 to 460 nm region, and re-emits an optical wavelength of 500 to 580 nm to increase energy conversion of the solar cell device by 20 to 50%.

The epoxy (-COC-) group or the silicon-organic compound (-CO-Si-C-) group polymer has a maximum M = 25000 carbon units at a molecular weight of M = 10000 carbon units and a reflectance of n = 1.35 at a maximum n = 1.65 It exists in the range of, It is characterized by using what hardens at the temperature of 80-180 degreeC.

The green light-emitting phosphor is based on the orthorhombic solid solution phase of the IIA group cationic element activated by the rare earth element of Eu ⁺² , Ce ⁺³ , or Dy ⁺³ and has the following stoichiometry .

(Stoichiometry)

(∑Me ⁺² ) ₈ Si ₄ O ₁₆ : ∑Ln ^{+ 2, + 3} , in this equation

∑Me ⁺² = Ca ⁺² and / or Sr ⁺² or Ba ⁺² and / or Mg, and ∑Ln = Eu ⁺² and Ce ⁺³ and / or Dy ⁺³

The green light-emitting phosphor is characterized by being composed of atomic sharing of [Mg] = 0.01 ~ 0.05, [Ba] = 0.5 ~ 0.8, [Sr] = 0.05 ~ 0.1 when the content of the rare earth element as an activator is 0.05-5% atom. Shall be.

The excitation spectrum of the green light emitting phosphor is in the region of UV and blue light, the spectral maximum light emission wavelength is in the range of 505 to 545 nm, the maximum light emission for high spectral brightness is 10 mW / nm or more, and the concentration of the green light emitting phosphor in the optical converter is It is characterized in that 0.25 to 10 wt%.

The silicon particles have a geometric size of 2 to 50 nm, an apparent density of 1.0 g / cm ³ or less in a spherical-ellipse form, and a concentration of nano silicon particles in the optical converter is 0.1 to 1 wt%.

In another embodiment, the green emission spectrum converter is formed of a module that generates power by coating the entire surface of a polycrystalline silicon solar cell device, and has an open voltage of 1.5 to 2.4% and a short circuit current density of 4.4 to about electrical parameters. It is achieved by providing a polycrystalline silicon solar cell device coated with a green light emission spectrum converter, characterized in that 20%, the charging rate is increased by 1 to 20.7%, and the total efficiency increase is 10 to 46.5%.

The module is a combination of 36 to 72 cells, characterized in that the cells are connected in series or parallel circuit configuration .

The polycrystalline silicon solar cell device is characterized in that the wafer is made of a thin film polycrystalline silicon wafer having a thickness of 120 ~ 260μm.

The polycrystalline silicon solar cell device is characterized by reducing the reflectance of the UV light by 20 to 80% by coating the green emission spectrum converter.

The present invention is coated on the front surface of a polycrystalline silicon thin film wafer with an electrical pn junction with a green light emission spectrum converter made of a polymer film in the form of a thin film to significantly increase the efficiency of the polycrystalline silicon solar cell device As a result, a polycrystalline silicon solar cell device having a low production cost can be produced with high efficiency without using a single crystal silicon solar cell device.

In particular, the green light emission spectrum converter in the form of the coated polymer film contains a nano-sized green light emitting phosphor having a composition concentration of 0.25 to 10% mass and a composition of semiconductor silicon, and includes light absorption in a short wavelength region including a UV region. At the same time, it is a useful invention having the advantage of increasing the efficiency of a polycrystalline solar cell device by emitting light in a region of 500 to 580 nm, and is an invention which is expected to be greatly used in industry.

Hereinafter, the configuration and the operation of the embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

1 is a graph showing spectral reflection within a range of 300 to 1000 nm of a polycrystalline silicon cell device before and after coating of a green light emission spectrum converter according to the present invention, and FIG. 1 (a) shows an initial polycrystalline silicon cell device before converter coating. Shows spectral reflection within the range of 300 to 1000 nm, and FIG. 1 (b) shows the spectral reflection within the range of 300 to 1000 nm of the polycrystalline silicon solar cell element after the converter coating.

First, FIG. 1A illustrates surface reflection of an antireflective Si ₃ N ₄ thin film on poly-silicon. Through 16 test cells, the typical reflection is about 30-33% for 500-700 nm. Rather high reflectivity indicates that it is not easy to obtain less reflection using the Si ₃ N ₄ layer on the poly-silicon surface in the broad spectral region. Such high reflectivity with the Si ₃ N ₄ layer means that it is too difficult to achieve high efficiency in poly-silicon photovoltaic cells and the majority of radiation loss from the wafer is an essential part of the efficiency loss.

At short wavelengths in the 300-500 nm region, the reflectivity is higher, reaching about 40%.

In the 500-700 nm region, the reflectivity increases again after showing a relatively gentle reflection line. Small fluctuations in reflectivity can also be observed. For example, the reflectivity decreases in the 940-960 nm region and then increases again in the 980 nm region.

This is typical of the converter's precoating curves for the initial 16 samples of polycrystalline silicon solar cell devices.

In addition, referring to FIG. 1B according to the present invention, a decrease in short wavelength reflectance can be seen first in a 300 to 500 nm region. Graphical integration of the differences in the spectral curves of FIGS. 1A and 1B indicates that the reflectance is reduced by more than two times in the short wavelength region.

Green emission spectrum converter emission can be observed in the blue-green spectral region where the spectral maximum is located at 508-512 nm. This spectral maximum half-width is 70-80 nm and can be explained by the position of the nano-sized green light emitting phosphor in the converter volume. From the long wavelength end of the reflection region of the visible spectrum, we see that the reflection oscillation is 40-50% without a substantial increase in reflection. However, the integral of the reflectance for a coated wafer with a green emission spectrum converter is less than the integral of the reflectance for a wafer without a converter.

Therefore, the green emission spectrum converter reduces the reflectance to increase the radiation occupancy to the polycrystalline silicon solar cell wafer, which enhances the optical efficiency of the polycrystalline silicon solar cell device.

It can be seen that the reflection between the wafer with the green emission spectrum converter and the wafer without the wafer is about doubled. Green emission spectrum converters therefore reduce the reflection of useful optical excitation spectra.

As such, most of the solar radiation interacts with polycrystalline silicon wafers, which can be seen to be accompanied by increased generation of opto-electrical currents. In addition, the location of the maximum green light range of 500-550 nm increases the number of light that hits the wafer surface. The additional green quantum is located in the region close to the optimal light response of the poly-silicon.

The conclusion of this experimental fact is the increase in the electrical current generated by the polycrystalline silicon device. As shown below, all possible processes take place in polycrystalline silicon and the conversion efficiency of solar radiation increases simultaneously with the electrical parameters of the solar cell device (opening voltage, short-circuit current density, fill factor).

This general phenomenon is related to the green light emitting phosphor used in the green light emission spectrum converter structure. However, nanoparticles of semiconductor silicon are also included in the green emission spectral converter.

As can be seen from what optical phenomena can be caused by nanoparticle semiconductor silicon, nanosilicon is a very powerful absorber of solar short-wave radiation. It is related to the energy gap of silicon equal to 1.1 eV.

Since the short wavelength solar spectral energy is 2.2-3.6 eV, the nanoparticles of silicon easily absorb the short wavelength solar spectrum. Increasing the amount of silicon particles also increases the absorption of solar radiation in the spectral range from 300 nm up to 400 nm. The silicon particles re-emit the absorbed short wavelength radiation in the visible or infrared range.

However, experiments with polycrystalline silicon cells coated only with nano silicon without green light emitting phosphors show that the addition of nano silicon particles increases the open voltage. At the same time this also increases the short-circuit current density. It can be assumed that the addition of nano silicon particles (grains) involves the current conducting chain of nano silicon particles at the inside and boundary of the wafer surface. These electrically conductive silicon particles can join the heterogeneously oriented blocks of the polycrystalline silicon crystal device into a homogeneous device. This changes the overall conductivity or electrical parameters of the device.

The effect of the presence of nano silicon particles on the properties of polycrystalline silicon solar cell devices is described below. From the summarized experimental data, the action of the unit green emission spectrum converter in contact with the front surface of the polycrystalline silicon solar cell device is as follows.

-Increased reflection radiation sharing in the infrared and short wavelength regions

An increase in green luminescence share and the emergence of green spectral luminescence in the range greater than 500 nm

-Changes in Total Electrical Conductivity of Polycrystalline Silicon Solar Cell Wafers

Such optical-electrical parameter changes of polycrystalline silicon solar cell devices have not been described in other literature.

This unique feature can be realized in polycrystalline and monocrystalline solar cell devices based on thin film wafers from 120 to 260 μm thick. The polycrystalline silicon wafer mentioned contacts a green emission spectrum converter of 50 to 250 μm thickness and phosphors and nano silicon particles are present in the volume of the converter up to 1/500 to 1/1000 of the green emission spectrum converter layer.

Firstly, the green emission spectrum converter is a two-dimensional parallel device in contact with a polycrystalline silicon wafer. As a thin film coated on a wafer, the thickness of the green emission spectral converter can be comparable to the wafer thickness.

However, green emission spectral converters are polymer structures with inorganic phosphors and silicon in at least two solid materials, specifically hetero-phase polymers. Both solid materials are nano sized.

If the maximum thickness of the green emission spectral converter is 260 μm, up to 260-520 nm particles of solid material are distributed in the converter volume in the secondary phase. If the green emission spectral converter is a thinner layer, for example 50 μm, the phosphor and silicon particle sizes should be between 50 and 100 nm. That is, as the thickness of the green emission spectral converter decreases, the size of the solid material in the hetero-phase converter must also be reduced.

Two solid materials, namely fillers, are nano-sized, which have unusual properties typical of nano-objects.

The first feature of nano-sized particles is to involve changes in the physical light dispersion model. When the particle faces the excitation radiation wavelength, high optical dispersion can be observed according to the dispersion of physic Mu, that is, nano-sized particles according to the relay law whose dispersion ratio is proportional to the particle size.

According to the relay law, the light dispersion of nanoparticles is very low. This conclusion is shown by the fact that the excitation solar radiation reaches the wafer surface with low dispersion loss.

A second feature of the nanoparticles is the self-organization capability of the green emission spectral converter according to the invention, ie the possibility of forming spontaneously ordered structures within the volume of the green emission spectral converter. This structure of green luminescent phosphors and silicon particles filled in the spectral converter volume also largely affects the physical properties of the optoelectronic device.

This kind of abnormal phenomenon occurs in polycrystalline silicon solar cell devices with optically active green emission spectrum converters, and the materials of the mentioned green emission spectrum converters strongly absorb short wavelength solar radiation in the range of It emits a wavelength in the range of 500-580 nm, which increases the conversion efficiency of solar radiation in solar cell devices by 20-50%.

The physical base of this phenomenon has been described above and an intrinsic reduction in short wavelength reflection has been noted in devices with green emission spectral converters. Thus re-luminescence is observed in the spectrum shown according to FIG. 1. In this respect, the present invention is concrete. All the phenomena can be observed in polycrystalline silicon solar cell devices with green emission spectrum converters and the conversion efficiency is increased by 20-50%.

Typical efficiencies of polycrystalline silicon solar cell devices without green emission spectrum converters are about 9-11%. Meanwhile, a polycrystalline silicon solar cell device in which a layer is formed only of a polymer without silicon and a phosphor as a charging component shows another property.

This is an important experimental appendix, demonstrating that all abnormal properties are inherent in hetero-phase and multicomponent converters.

The effect of that kind of green emission spectral converter according to the invention can be realized in a polycrystalline silicon solar cell device in which the optically active converter is in direct contact with the wafer and the direct contact of the optically active converter to the wafer is the wafer spectrum. This results in a 20% to 80% reduction in the reflection of the UV region, while increasing the open-voltage, short-circuit current density with the help of phosphors and silicon as fillers in the composite converter and increasing the fill factor up to 0.72.

In the course of the study according to the invention it was found that the change in the optical parameters or electrical properties of the polycrystalline silicon solar cell device is controlled by the mentioned optical specifications. It has also been found that the reduction of wafer reflection in the short wavelength spectrum is accompanied by an increase in open voltage and an increase in short circuit current density. As shown below, this change increases by 2-10% in the parameters, which coincide with the concentration of phosphor and nanosilicon as fillers in the optically active converter. The increase in the concentration of phosphor and silicon can be indicated by an integration parameter such as the fill factor FF.

The initial value of the device's fill factor is below 0.68, but after coating of the converter, this integral fill factor increases up to 0.72.

Specific values for the tested wafers are shown in Table 1 below. The basic electrical parameters of the polycrystalline silicon solar cell device are increased by up to 10% by using the proposed green emission spectrum converter and the overall efficiency is increased by up to 20-50%. Similar results are not found in previous studies, demonstrating the importance and priority of the proposed invention.

This advantage can be realized in photovoltaic polycrystalline silicon solar cell devices with polymer materials, ie, green emission spectrum converters. The polymer constituting the green emission spectrum converter is an epoxy (-COC-) group or a silicon-organic compound (-CO-Si-C-) group having an average molecular weight of M = 10000 to 25000 carbon units and a refractive index of n = 1.35 to 1.65. It consists of thermal curing.

Looking at the above in detail, first, the connection base for the green light emission spectrum converter is a polymer epoxy (-COC-) group or a polymer silicon-organic compound (-CO-Si-C-) group. It is a very widely used polymer and is manufactured by many chemical companies around the world. We chose polymers with molecular weight M = 10000-25000 carbon units. Polymers with such molecular weights have high mobility in the liquid phase and are easily mixed with green luminescent phosphors and nano silicon particles. The polymer is thermally cured within 1 to 3 hours at T = 110-150 ° C. to maintain high optical transparency. The thermal expansion of the polymer is similar to that of poly-silicon (αT = 6 * 10 ⁻⁷ g ⁻¹ ).

In addition, an important feature of the polymer constituting the green emission spectrum converter according to the present invention is the refractive index of the cured phase. The refractive index for the epoxy polymer is usually n _o = 1.58. On the other hand we chose a silicon-organic polymer with a refractive index of n = 1.42. Such low values of refractive index reduce the reflection of the converter layer allowing the reflectivity to reach 25% or less over the entire wavelength region. This can essentially reduce the reflection value from silicon wafers with conventional coatings made of Si ₃ N ₄ , which can achieve transparency at λ = 550-630 nm, precisely in narrow spectral regions.

This very important advantage of the green emission spectral converter and the material of the proposed structure can be applied to polycrystalline silicon solar cell devices. The green luminescent phosphor contained in the green luminescence spectral converter volume is made based on the orthorhombic solid solution phase of the IIA subgroup silicate having the following stoichiometry and activated by the rare earth elements Eu ⁺² , Ce ⁺³ , Dy ⁺³ .

(∑Me ⁺² ) ₈ Si ₄ O ₁₆ : ∑Ln ^{+ 2. + 3} , where

∑Me ⁺² = Ca ⁺² and / or Sr ⁺² or Ba ⁺² and / or Mg ⁺² ,

and ∑Ln ^{+ 2, + 3} = Eu ⁺² and Ce ⁺³ and / or Dy ⁺³

As one of the fillers of the proposed converter, a green light emitting phosphor having an emission wavelength of λ = 490 to 580 nm is used. The spectral maximum half-width of this phosphor is Δλ _0.5 = 55 ± 3 nm and the maximum spectrum has a narrow spectral range of λ = 512 to λ = 525 nm as shown in FIG. Light emission in this spectral range is more preferred with respect to the spectral response of the polycrystalline silicon material.

The selected green light emitting phosphor exhibits the most effective green light emission after excitation by solar radiation. The requirements for the green luminescent material are as follows.

Optical excitation within the range of 440 to 480 nm

-high quantum yield of ζ≥ 0.75

High spectral luminous density above 10 mW / nm

High stability against solar radiation without photolysis

High thermal stability of phosphor luminescence with no decrease in stability to heating up to 50 ~ 60 ℃

The most suitable material to meet all these requirements is an orthorhombic structure of orthorhombic structure with stoichiometric ∑ (Mg, Ca, Sr, Ba) ₈ Si ₄ O ₁₆ : ∑Eu ⁺² , Ce ⁺³ , Dy ⁺³ .

This phosphor is associated with a conventional group of luminescent materials and the main specification is determined by the activating ions placed in the crystal field of the phosphor grating. In our case, the activated ions are Eu ⁺² and Ce ⁺³ and Dy ⁺³ are added as sensitizer ions located at the asymmetric point of the ortho silicate lattice. This asymmetric point is determined by the presence of four heterogeneous cation sites such as Mg ⁺² , Ca ⁺² , Sr ⁺² , Ba ⁺² . These ions are surrounded by tetrahedron [SiO ₄ ] groups coordinated around the cation site. The majority of such tetrahedrons are located around the largest cation site Ba ⁺² and a few are located around Mg ⁺² .

This makes the crystal lattice of the proposed phosphor additionally heterogeneous but facilitates to increase the quantum yield.

Synthesis of the proposed phosphor is achieved by using hydrochlorides of Mg, Ca, Sr, Ba, Eu as the initial reactants and sol-gel combination of tetra-eta-silane, Si (OC ₂ H ₅ ) ₄ , hydrolyzed with sedimentant. Can be. The chemical reaction of phosphor production can be established as follows.

8∑Me ⁺² + 4H ₂ SiO ₃ (+ C ₂ H ₅ OH) → ∑Me ₈ Si ₄ O ₁₆ + C ₂ H ₅ OH

The main advantage of the production of ortho silicate phosphors with the proposed chemical formulation is basically that the chemical composition is easily regulated and the phosphors can be easily obtained. The product deposited according to the reaction must be washed with ethanol through filtration. And put into the crucible [H ₂ + N ₂ (97%)] should be calcined at T = 900 ℃ ~ 1100 ℃ for 4-6 hours in a reducing atmosphere. The calcined phosphor is cooled, washed with dilute hydrochloric acid and dried. Phosphor particles look like plates of 50-200 nm in size. The synthesized phosphor is excited with 395 nm UV light and blue light to emit bright green light.

This is an intrinsic advantage of the material proposed as one component of the green emission spectrum converter of polycrystalline silicon solar cell devices and the green emission phosphor contains the following base.

0.01 ≤ [Mg] ≤ 0.05 atomic shares,

0.01 ≦ [Ca] ≦ 0.1 atomic shares,

0.05 ≦ [Sr] ≦ 0.1 atomic shares,

0.5 ≤ [Ba] ≤ 0.8 atomic shares,

Substitution of a portion of the basic cation Ba ⁺² with Sr ⁺² involves a long wavelength shift of the main maximum emission. At the same time the addition of Ca ⁺² is accompanied by an increase in the red component in the phosphor emission. Substitution of part of Ba ⁺² with Mg ⁺² involves a short wavelength shift in phosphor emission. Eu ⁺² fd junctions as basic activating ions in the phosphor can be used to provide spectral maximum emission in the green spectral range.

Ce ^{+ 3} and Dy ^{+ 3} ions must be added to the base composition in addition to less than 1% of the atomic share of Eu ^{+ 2} (0.05-5%) in order to increase the luminous output.

The proposed phosphor, together with the nanosilicone and curable polymer in the spectral converter, emits a strong emission in the green spectral range. This additional light emission with a spectral maximum within the range of silicon photo-sensitization is a likely cause of increased efficiency of the proposed solar cell. At the same time, green phosphor emission as a component of the converter enhances all electrical parameters of the proposed polycrystalline silicon solar cell device. As already noted, the increase in parameters can reach 2 to 10% and the efficiency increase can reach 10 to 46.5%.

Higher parameters can also be achieved in the proposed polycrystalline silicon solar cell device in which the excitation spectrum of the green light emitting phosphor, which is a component of the spectral converter, is in the range of UV and blue radiation and the phosphor spectral luminance is 10 mW / nm or more. For example, when the concentration of the green light emitting phosphor in the green light emission spectrum converter is 0.25 to 10% mass, the maximum spectrum thereof is in the range of 505 to 545 nm.

The proposed ortho silicate phosphor has high energy spectral luminance within the range of 505 to 545 nm. If the half-width of luminescence is 57 nm, this value is very high, above 10 mW / nm. When solar radiation hits the wafer surface at 1 watt power with a wavelength of 395 nm (UV) to 470 nm (blue light), the phosphor emits more than 570 mW with green light emission. Since the proportion of the blue (λ = 485 nm) and orange (585 nm) regions in the phosphor spectrum is up to 5%, it is difficult to measure this value more accurately.

As mentioned above, the green light-emitting phosphor has a quantum yield (ζ ≧ 0.75) of 0.75 or more. On the other hand, only a few of the best known green phosphors available outperform the quantum yields of ζ = 0.60 to 0.70.

The concentration of the green light emitting phosphor in the volume of the green light emission spectrum converter is very important. This concentration should be in the range of 0.25-10% mass. If the concentration of the green light-emitting phosphor is less than 0.25%, the increased luminous efficiency is too low, so the influence of the converter on the electrical parameters of the solar cell is also low. On the other hand, if the concentration of the green light emitting phosphor in the converter is higher than 10%, it reduces the additional non-active absorption of the excitation light by the phosphor particles, thereby reducing the electrical parameters of the photoelectric device.

Repeated experiments found that the optimal concentration of phosphor ranged from 1 to 5% mass. This concentration value depends on the initial polymer viscosity of the spectral converter. The viscosity of the converter base material spontaneously affects the aggregation of phosphor particles. This phenomenon will be considered in detail in future studies.

As mentioned above, the addition of semiconductor silicon particles in the green emission spectral converter volume involves a change in the active conductivity (or resistance) of the polycrystalline silicon solar cell device. Increasing conductivity decreases the open voltage and is not always desirable. On the other hand, the change in the concentration of the silicon particles which increases the direct resistance of the polycrystalline silicon solar cell element can be accompanied by an increase in the open voltage. The most suitable size of nano silicon to be applied to solar cell devices is in the range of 10 to 30 nm. Such silicon particles made by plasma chemistry have a spherical-ellipse shape as shown in FIG. 3. The optimum apparent density of nanosilicon is 1 g / cm ³ or less (ρ ≦ 1 g / cm ³ ).

The concentration of nano silicon above 1% mass can increase the resistance of polycrystalline silicon solar cell devices from 90 ohms up to 170 ohms. At the same time, the open circuit voltage is reduced up to 0.59 V for solar cell elements with a surface area S = 12 cm ² .

If the concentration of nanosilicon in the green emission spectral converter is less than 0.1% mass ([Si] ≤0.1% mass), the open voltage increases but at the same time the short circuit current density decreases. The optimal concentration of nano silicon in the optical converter is about 0.4-0.7% mass. In this concentration range, the open-voltage and short-circuit current densities increase while the direct resistance does not change.

The improvement of such parameters is that the nano silicon particles, which are components of the optically active converter, are in the form of a sphere-ellipse with a geometric size of 2-50 nm and an apparent density of ρ = 1 g / cm ³ or less, and their concentration in the converter is 0.1-. It can be realized in polycrystalline silicon solar cell devices in the range of 1% mass.

All parameters of the polycrystalline silicon solar cell devices according to the invention are measured for each device with a standard solar simulator at AM1.5, before and after coating of the green emission spectrum converter. The test results are shown in Table 1. For testing, several polycrystalline silicon solar cell devices with an open voltage of Voc = 0.56 V to 0.588 V were used.

The filling rate may vary in the range of FF = 0.4128 to 0.6574. The short circuit current density is in the range of Jsc = 27 to 30.54 mA. In addition, the total efficiency parameter is in the range of ζ = 6.37% to 11.4238% and the electrical resistance of the devices is in the range of R = 65 to 102 Ohm (Ω).

Table 1 Parameters of Polycrystalline Silicon Solar Cell Devices

Before coating of converter After coating of onverter Additive ratio ¹ No Voc FF ζ Jsc Ω Voc FF ζ Jsc One 0.5849 0.6574 11.4238 29.7070 97-102 0.5940 0.6640 12.5860 30.9800 0.9 / 0.05 2 0.5688 0.6157 10.3056 29.4291 88-94 0.5742 0.6933 11.1034 30.0623 1.9 / 0.2 3 0.5664 0.6499 10.6908 29.0440 95-96 0.5799 0.6725 11.7419 30.1072 2.9 / 0.5 4 0.5730 0.6448 10.9557 29.6501 98-94 0.5755 0.6689 11.5380 30.0010 3.9 / 0.6 5 0.5827 0.6125 10.9015 30.5464 92-94 0.5823 0.6658 12.0772 31.1621 4.9 / 0.8 6 0.5849 0.6574 11.4238 29.7070 98-100 0.5990 0.6640 12.5860 31.0000 5.0 / 1.0 7 0.5880 0.5804 10.2425 30.0158 87-90 0.5887 0.6481 11.9223 31.2655 3.0 / 0.16 8 0.5859 0.6092 10.6296 29.7811 85-88 0.5787 0.6726 12.0454 31.0200 2.6 / 0.6 9 0.5712 0.4128  6.3699 27.0057 65-99 0.5747 0.4983 9.3446 32.6361 3.0 / 0.03 ¹ phosphor / nano-Si,% /%

The conversion of a typical polycrystalline silicon solar cell device into an optically converted polycrystalline silicon solar cell device consists of three components: a polymer bond, a nano-sized green light emitting phosphor, and a nano silicon particle.

By analyzing the displayed data, the following conclusions can be drawn:

-1.5-2.4% increase in open voltage for devices with converters

4.4-20% increase in short-circuit current density

-1 ~ 20.7% increase in charge rate

-10 to 46.5% increase in total efficiency

-The electrical resistance of the polycrystalline silicon solar cell device is changed from 2 to 12 ohms in the most increasing direction

As shown in Table 1, the result is very high. The I-V curve of the solar cell device without the green emission spectrum converter is shown in FIG. 2. 2, curve (a) corresponds to the initial state of the polycrystalline silicon solar cell device before coating and curve (b) corresponds to the device with the green emission spectrum converter according to the present invention.

In order to increase the parameters, several solar cell elements are combined into a module, typically 36 elements. That is, a module consists of 36 or 72 elements, rarely 144 elements. The solar panel is a combination of 36 elements, 6 inches by 6 inches.

All devices are equipped with a green emission spectral converter developed in accordance with the present invention. If the conductivity of the devices is homogenized to ΔR ≦ ± 3%, it is possible to obtain a high quality combination.

In the module, polycrystalline silicon solar cell elements are connected in series-parallel chains.

The parameters of the mentioned combinations are shown below.

Max power, W 108

-Maximum voltage, V 18.6

-Number of cells 36

Efficiency 14.6%

This is a very high value for polycrystalline silicon devices. The company plans to start mass production of the proposed polycrystalline silicon solar cell devices.

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by any person having ordinary skill in the art without departing from the gist of the present invention claimed in the claims. Of course, such changes will fall within the scope of the claims.

1 is a graph showing the spectral reflection within the range of 300 ~ 1000 nm of the polycrystalline silicon cell device before and after the spectral converter coating according to the present invention,

2 is a graph showing typical data of I-V coordinates with or without converter coating of a polycrystalline silicon solar cell device.

3 is a SEM photograph of the nano-silicon according to the present invention,

4 is a graph showing the emission spectrum of the green light-emitting nanophosphor according to the present invention,

5 is a photograph of a commercially available polycrystalline silicon solar cell device.

Claims (13)

0.25 to 10 wt% green light-emitting phosphor, 0.1 to 1 wt% silicon particles, and the remainder is composed of an epoxy (-COC-) group or a silicon-organic compound (-CO-Si-C-) group polymer to be 100 wt% Make up, The green light emitting phosphor is based on an orthorhombic solid solution phase of an IIA group cationic element activated by a rare earth element of Eu ⁺² , Ce ⁺³ , or Dy ⁺³ , and has a stoichiometric formula as follows. Green emission spectrum converter. (Stoichiometry) (∑Me ⁺² ) ₈ Si ₄ O ₁₆ : ∑Ln ^{+ 2, + 3} , in this equation ∑Me ⁺² = Ca ⁺² and / or Sr ⁺² or Ba ⁺² and / or Mg, and ∑Ln = Eu ⁺² and Ce ⁺³ and / or Dy ⁺³ The method according to claim 1, The green light emission spectrum converter is coated with a thickness of 50 to 250 μm, and the size of the green light emitting phosphor and nano silicon particles in the converter is up to 1/500 to 1/1000 of the converter thickness. Converter. The method according to claim 1, The green light emission spectrum converter strongly absorbs short wavelength solar light in the 300 to 460 nm region, and re-emits an optical wavelength of 500 to 580 nm to increase the energy conversion of the solar cell device by 20 to 50%. Spectrum converter. The method according to claim 1, The epoxy (-COC-) group or the silicon-organic compound (-CO-Si-C-) group polymer has a maximum M = 25000 carbon units at a molecular weight of M = 10000 carbon units and a reflectance of n = 1.35 at a maximum n = 1.65 Green emission spectrum converter which exists in the range of and uses what hardens | cures at the temperature of 80-180 degreeC. delete The method according to claim 1, The green light-emitting phosphor is characterized by being composed of atomic covalent of [Mg] = 0.01 ~ 0.05, [Ba] = 0.5 ~ 0.8, [Sr] = 0.05 ~ 0.1 when the content of rare earth element as an activator is 0.05-5% atom Green emission spectrum converter. The method according to claim 1, The excitation spectrum of the green light-emitting phosphor is in the region of UV and blue light and the maximum wavelength is in the range of 505 to 545 nm when the concentration of the wavelength is 0.25 to 10% mass, and the maximum light emission for high spectral brightness when the region is 505 to 545 nm. The green emission spectrum converter, characterized in that 10 mW / nm or more. The method according to claim 1, The size of the silicon particles is a green emission spectrum converter, characterized in that 10 ~ 30 nm. The method according to claim 1 Wherein the silicon particles have a geometric size of 2 to 50 nm and an apparent density of 1.0 g / cm ³ or less in a spherical-ellipse form. Claim 1, 2, 3, 4, 6, 7, 8, 9 of the green light emission spectrum converter is formed of a module that is coated on the front surface of the polycrystalline silicon solar cell device to generate power, the electrical parameter is open Green light emission spectrum converter-coated polycrystalline silicon solar cell device, characterized in that the voltage is 1.5 ~ 2.4%, the short circuit current density is 4.4 ~ 20%, the charging rate is increased by 1 ~ 20.7%, the total efficiency increase is 10 ~ 46.5% . The method according to claim 10, The module is a combination of 36 to 72 cells, the green light emission spectrum converter-coated polycrystalline silicon solar cell device, characterized in that the cells are connected in series or parallel circuit configuration. The method according to claim 10, The polycrystalline silicon solar cell device is a polycrystalline silicon solar cell device coated with a green light emission spectrum converter, characterized in that the wafer is made of a thin film polycrystalline silicon wafer having a thickness of 120 ~ 260μm. The method according to claim 10, The polycrystalline silicon solar cell device is a green light emission spectrum converter coated polycrystalline silicon solar cell device, characterized in that to reduce the reflectance of the UV light by 20 to 80% by coating the green light emission spectrum converter.

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