CN102368538A - Organic film solar battery capable of enhancing light absorption efficiency - Google Patents

Abstract

The invention provides an organic film solar battery capable of enhancing a light absorption efficiency. The organic film solar battery comprises: a transparent substrate (1); a transparent electrode (2), which is deposited on the glass substrate; a cavity transmission layer (3), which is spinnedly coated on the transparent electrode (2); a nanometer metal structure (4), which is prepared in the cavity transmission layer (3) and enables light absorption to be enhanced; a photolytic activity layer (5), which is manufactured by organic semiconductor high-molecular materials and is spinnedly coated on the surface of the cavity transmission layer (3); and a metal back electrode (6). According to the invention, on the basis of a design on parameters of a nanometer metal structure, a wave band of an electromagnetic wave in the sun lights is coupled and is penetrated into the film, wherein the wave band of the electromagnetic wave can be best absorbed by an organic material of a photolytic activity layer; a light absorption efficiency of an organic film solar battery is enhanced to the most degree; and a photoelectric conversion performance of the organic film solar battery is improved basically.

Description

A kind of organic thin film solar cell that can improve efficiency of light absorption

Technical field

The present invention relates to a kind of organic solar batteries, particularly a kind of organic thin film solar cell that can improve efficiency of light absorption.

Background technology

In recent years, the human environment problem is increasingly sharpened, and for solar energy provides wide space in development in future, as the device that can transform light energy be become electric energy, solar cell becomes focus wherein of greatest concern naturally.Since solar cell is invented first by AT&T Labs in 1954; So far crystal silicon solar energy battery, thin-film solar cells and three developing stage of novel solar battery have been experienced; Basic target is exactly constantly to reduce manufacturing cost, farthest improves photoelectric conversion efficiency.

As one of representative of novel solar cell, organic solar batteries with its simple technology, low energy consumption, can use flexible substrate and realize that advantages such as large tracts of land manufacturing are more and more receiving various countries researcher's concern in recent years.Nowadays, the energy conversion efficiency based on the polymer organic materials for solar cells can surpass 6%.Yet for the conventional crystal silicon solar cell, this efficient is also very low; Cause the main cause of this phenomenon to be: the carrier mobility of organic material is low; Cause diffusion length to have only tens nanometers, avoid compound so the charge carrier that wants to inspire effectively transports, the thickness of photoactive layer will very thin (tens nanometers); But very thin photoactive layer can not absorb incident light fully, influences battery performance thereby cause efficiency of light absorption significantly to reduce.So, how to strengthen the efficiency of light absorption of organic photovoltaic battery, become this field development key.

Got into since 21 century, the micro-nano technology has obtained to develop rapidly, and problems such as science relevant under the micron/nano yardstick and application technology are intended to study in this field.Along with the continuous progress of micro-nano processing, control, detection technique means, the unusual optical phenomena of second wavelength metallic structure comes to light, and has developed out surface plasma bulk optics (Surface Plasmon Optics) rapidly thereupon.The substantive characteristics of surface plasma bulk optics is to be strapped in the free electron density ripple of metal surface transmission and the interaction between the electromagnetic field, and its research object is the metal structure under the sub-wavelength yardstick.This structure has special light field modulating characteristic, also extensively carries out in the application study of many technical fields.

So; A kind of way of feasible raising solar cell light absorption occurs; The local surface plasma (localized surface plasmons) that promptly utilizes the metal surface to excite; Its produce reason be since the surface of metal particles free electron of sub-wavelength dimensions with incident electromagnetic wave satisfying generation coupled resonance certain condition under, produced the electromagnetic wave of local in the metal surface, a part of electromagnetic wave energy wherein can blaze abroad through the form of scattering; This part electromagnetic wave that scatters out can be used for increasing the electromagnetic wave energy that solar cell receives, thereby increases the light absorption of battery.

This method has obtained good utilization in crystal silicon solar batteries and amorphous silicon thin-film solar cell, still also do not have being used in the organic solar batteries of system, particularly in the organic thin film solar cell of ultra-thin photoactive layer.Because the local surface plasma resonance characteristic of metallic particles depends mainly on size, cycle and the shape of nano-metal particle; Simultaneously resonance condition receives the influence of factors such as dielectric environment on every side again; In addition, battery self structure and material behavior also all can influence its performance.Also do not propose the research and the method for designing of a cover system so far to these mechanism, do not design the most perfect metallic particles structure applications in ultra-thin organic solar batteries yet.

Summary of the invention

Based on the deficiency that exists in the above-mentioned prior art; The technical problem that the present invention will solve is: overcome the low problem of present stage organic solar batteries efficiency of light absorption; Promptly, the diffusion length that satisfies the organic photoactive layer material reduced after its thickness technical problems such as the serious light absorption deficiency of caused organic solar batteries, decreased performance for requiring.

Technical scheme of the present invention is: a kind of organic thin film solar cell structure that can improve efficiency of light absorption is provided; Characteristics are design one deck nanometer metal structures in the hole transmission layer of organic solar batteries; Utilize metal structure, the local surface plasma resonance that excites through incident electromagnetic wave strengthens the light absorption of organic thin film solar cell.Particular content is following:

Technical scheme 1, be illustrated in figure 1 as the structure of light absorption enhancement mode organic thin film solar cell, shown in figure, a kind of organic thin film solar cell that can improve efficiency of light absorption, the structure of said battery is respectively from top to bottom:

Transparent substrates 1;

Transparency electrode 2 is layer of transparent conductive layers, is deposited on the glass substrate, and it is as the anode of said battery structure, and material is tin indium oxide (ITO);

Hole transmission layer 3 is spun on the transparency electrode 2;

Nanometer metal structure 4, it is prepared in hole transmission layer 3 inside, can realize that light absorption strengthens;

Photoactive layer 5, it is the organic semiconductor macromolecular material, is spun on hole transmission layer 3 surfaces;

Metal back electrode 6 is used to reduce the negative electrode work function, helps electric transmission;

Wherein, Said nanometer metal structure 4 is a periodicity Ag metal nanoparticle; Said periodicity Ag metal nanoparticle can strengthen the efficiency of light absorption of organic thin film solar cell; Obtain according to Mie is theoretical: when incident electromagnetic wave satisfies following condition with metallic particles self structure parameter, can be with the free electron generation coupled resonance of surface of metal particles:

${\mathrm{\ϵ}}_m=-\frac{L+1}{L}{\mathrm{\ϵ}}_D---\left(1\right)$

In the formula, ε _mReal part of permittivity for metal;

ε _DReal part of permittivity for the metallic particles surrounding environment;

L is an integer, and the exponent number of resonance takes place in expression;

So coupled resonance has formed the strong-electromagnetic field of local in surface of metal particles; Also be called as the local surface plasma resonance; Energy of electromagnetic field is divided into two parts during resonance; A part is absorbed by metallic particles self, and another part can be gone out through beyond-the-horizon communication, promptly so-called resonance absorption and resonance scattering; Based on formula (1), the design metallic particles is in solar battery structure, and the electromagnetic scattering that utilizes resonance scattering effect to let resonance produce gets in the photoactive layer, has increased the light intensity that the unit are photoactive layer receives, thereby has improved efficiency of light absorption;

Photoactive layer in the said photoactive layer 5 is the 35nm ultrathin; Can finely must satisfy the requirement of organic semiconducting materials charge carrier diffusion length, make carrier transport efficient remain on very high level, the resonance scattering through described nanometer metal structure strengthens optical absorption again; Make that the efficiency of light absorption of photoactive layer material is suitable when not only stack pile is big; And the charge carrier that produces can better transport and avoid compound, thereby improved the battery internal quantum efficiency, promotes battery performance.

Technical scheme 2, according to technical scheme 1 described Ag metallic particles; The Ag metallic particles that it is characterized by in the said periodicity Ag metal nanoparticle structure is the spheroid of fixed diameter 100nm; This size can make local surface plasma resonance intensity reach maximum and scattering strength at this moment occupies leading much larger than absorption intensity; Reach maximum so get into the electromagnetic intensity of photoactive layer through scattering; Thereby farthest improve the efficiency of light absorption of organic thin film solar cell, this is based under the situation of higher order mode existence, the scattering (C of metallic particles local surface plasma resonance cross section _Sca) and absorb (C _Abs) relation of formula and the two intensity and metal particle size:

$C_{\mathrm{sca}}={\mathrm{<figure-callout\; id="1"\; label="C\; sca"\; filenames="HDA0000092170430000011.png"\; state="\{\{state\}\}">C</figure-callout>}}_{\mathrm{sca}}+{\mathrm{\&Sigma;}}_{i=2}^{\&infin;}{C}_{\mathrm{sca}1}---\left(2\right)$

$C_{\mathrm{abs}}={\mathrm{<figure-callout\; id="1"\; label="C\; abs"\; filenames="HDA0000092170430000011.png"\; state="\{\{state\}\}">C</figure-callout>}}_{\mathrm{abs}}+{\mathrm{\&Sigma;}}_{i=2}^{\&infin;}{C}_{\mathrm{abs}1}---\left(4\right)$

In the formula, D is the metallic particles diameter;

C _ScaAnd C _AbsBe respectively Ag metallic particles cross section total scattering and absorption;

C _Sca1And C _Abs1Be respectively the scattering and the absorption of Ag metallic particles cross section dipole resonance;

and

Ag metal particles were cross-sectional view of the high order mode resonance superposition of scattering and absorption values.

At first, the explanation of above-mentioned (3), (5) formula increases with particle size, and the raising of cross section scattering strength is faster, can in resonance, occupy leading gradually along with the diameter increase; And the result of calculation of (2), (4) formula shows; Along with diameter continues to increase; Though the accumulated value of second the high-order resonance in two formula equal signs the right can increase; But first the dipole resonance intensity in equal sign the right can reduce, and in above-mentioned formula (2) to (5), exists the metallic particles diameter of an optimum to make resonance scattering reach maximum, and drawing the optimum metallic particles diameter that can make resonance scattering intensity reach peak value is 100nm; Can strengthen the light absorption of organic solar batteries this moment to greatest extent, raises the efficiency to greatest extent.

Technical scheme 3, according to technical scheme 2,100nm diameter Ag metallic particles is periodic arrangement, and the arrangement cycle is the fixed range of 150-500nm; Interval big or small at this through changing its cycle, regulate the local surface plasma resonance condition of metallic particles, thus can be according to the spectral absorption rule of battery photoactive layer material; And combine solar spectrum energy to distribute; Through the arrangement cycle of design metallic particles, the strongest scattering resonance condition is adjusted to the wavelength band that helps the photoactive layer absorbed most, at utmost improve the spectrum utilance of organic thin film solar cell; This electric resonance that is based between the metallic particles obtains: the metallic particles periodic arrangement; When incident electromagnetic wave shines, the inner polarized electric field that produces of metallic particles, polarized electric field can cause and produce electric resonance between the metal ball; And the energy density between the increase metal ball; The local surface plasma resonance condition changing that causes metallic particles, it is different that different cycle produces the electric resonance effect, but the cycle is too smallly caused serious being in the light; Excessive then do not have a modulation effect, can design in view of the above effective period scope and the method for utilizing the resonance of metallic particles periodic modulation to satisfy the absorbing rule of different photoactive layer organic materials.

A kind of absorbing properties that can improve the organic thin film solar cell of efficiency of light absorption provided by the invention can improve more than 20%.

The present invention compared with prior art beneficial effect is:

(1) the present invention is on traditional organic thin film solar cell basis; In hole transmission layer, increase nanometer metal structure, adopted the periodic array of large scale (100nm) Ag metallic particles first, can be when exciting the local surface plasma resonance; Eliminate the endergonic adverse effect of particle self; Make that the resonance scattering effect is the strongest, the electromagnetic intensity that excites that is coupled into the battery photoactive layer is maximized, at utmost improve the efficiency of light absorption of battery.

(2) designed the method for the arrangement periodic adjustment resonance condition that utilizes the 100nmAg particle among the present invention; Make that this structure can be to the absorbing rule of different light active materials; The adjustment arrangement cycle; The strongest resonance scattering is occurred in help the wave band that photoactive layer absorbs most, the nano-metal particle structure that makes this light absorption strengthen has very big design freedom.

(3) the photoactive layer thickness among the present invention satisfies the requirement of diffusion length; Film thickness only has 35nm; Compared with thick film of the prior art (greater than 100nm) battery better carrier transport efficient is arranged; And also suitable through nanometer metal structure effect optical absorption characteristics down with thick film properties, more promoted battery performance on comprehensively.

(4) periodic structure of metallic particles can utilize the preparation method of low energy consumption to realize among the present invention, and can more perfectly merge with traditional organic thin film solar cell technology, and processing is simple, and cost is low.

Description of drawings

Fig. 1 is a kind of organic thin film solar cell structural representation that can improve efficiency of light absorption provided by the invention; Wherein: transparent substrates 1; Transparency electrode 2; Hole transmission layer 3; Nanometer metal structure 4; Photoactive layer 5, metal back electrode 6;

Fig. 2 is that the light absorption based on photoactive layer material P3HT:PCBM strengthens the organic thin film solar cell structure chart in the specific embodiment; Wherein: 11 is glass substrate; 21 for thickness be the transparent ITO electrode of 150nm; 31 is the hole transmission layer of thickness 100nm; 41 is Ag particle cycle array; 51 is the photoactive layer of film thickness 35nm; 61 is the Al electrode;

Fig. 3 is in the specific embodiment, light absorption enhancement mode organic thin film solar cell absorption spectra (incident light scope: 350-800nm);

Fig. 4 is in the specific embodiment, the light absorption enhancing rate figure of light absorption enhancement mode organic thin film solar cell under the nanometer metal structure effect.

Embodiment

Introduce the present invention in detail below in conjunction with accompanying drawing and specific embodiment.But following embodiment only limits to explain the present invention, and protection scope of the present invention should comprise the full content of claim, and through following specific embodiment, those skilled in the art promptly can realize the full content of claim of the present invention.

Specific embodiment is a kind of organic thin film solar cell structure that can improve efficiency of light absorption, and is as shown in Figure 2.

Among Fig. 2,11 is glass substrate, and in addition, transparent substrates 1 also can be selected quartz for use; 21 for thickness is the transparent ITO electrode of 150nm, and as the anode of said battery structure, material is a tin indium oxide; 31 is the hole transmission layer of thickness 100nm, and its material is that macromolecular material gathers (3,4-vinyl dioxy thiophene) and gathers (styrene sulfonate) (PEDOT:PSS); 41 is Ag particle cycle array, is Ag spheric granules cycle array, particle diameter 100nm; 51 is the photoactive layer of film thickness 35nm, and its photoactive layer material selection gathers (3-hexyl thiophene) (P3HT) and 1-(3-methoxycarbonyl) propyl group-1-phenyl [6,6] C ₆₁(PCBM) blend film (P3HT:PCBM); 61 is the Al electrode, and in addition, metal back electrode 6 also can be selected for use: Ag or Ga/Al alloy.

The refractive index of photoactive layer material (P3HT:PCBM) is with wavelength variations in the present embodiment; And the refractive index imaginary part is in peak value at the 400-600nm wave band; So the spectrum of this wave band helps absorbed most; So will this wavelength band be adjusted in the resonance of metallic particles, at utmost improved efficiency of light absorption.

In conjunction with around dielectric environment (PEDOT:PSS) to the influence of metallic particles; Based on formula

and according to the influence rule of 4 said cycles of summary of the invention technical scheme to resonance, obtaining arranging cycle P based on the 100nmAg metallic particles of battery structure among the embodiment and material is 328nm.

To sum up, when Ag metallic particles diameter is 100nm, the cycle is when being 328nm; The ultra-thin organic solar batteries of 35nm based on photoactive layer material P3HT:PCBM; Through the numerical simulation of AM1.5 simulated solar irradiation, obtain the battery under this nanometer metal structure effect, at the 350nm-800nm visible-range; Average light absorbent properties when not having metal structure have strengthened 26%, absorb 6 times that strengthen in the subband of 400-600nm scope.This metallic particles structure is to absorb the optimum structure that strengthens to battery in the present embodiment.

Fig. 3 is that light absorption enhancement mode organic thin film solar cell is in the absorption spectra of 350-800nm incident light scope in the present embodiment, and dotted line is absorption corresponding when not having nanometer metal structure.

Fig. 4 for light absorption enhancement mode organic thin film solar cell than the absorption enhancing rate (ratio of absorption efficiency) of the conventional batteries that does not have nanometer metal structure when the different wave length.

Claims (5)

1. organic thin film solar cell that can improve efficiency of light absorption is characterized in that the structure of said battery is respectively from top to bottom:

Transparent substrates (1);

Transparency electrode (2) is the layer of transparent conductive layer, is deposited on the glass substrate, and it is as the anode of said battery structure, and material is tin indium oxide (ITO);

Hole transmission layer (3) is spun on the transparency electrode (2);

Nanometer metal structure (4), it is prepared in hole transmission layer (3) inside, can realize that light absorption strengthens;

Photoactive layer (5), it is the organic semiconductor macromolecular material, is spun on hole transmission layer (3) surface;

Metal back electrode (6) is used to reduce the negative electrode work function, helps electric transmission;

Wherein, Said nanometer metal structure (4) is a periodicity Ag metal nanoparticle; Said periodicity Ag metal nanoparticle can improve the efficiency of light absorption of organic thin film solar cell; Obtain according to Mie is theoretical: when incident electromagnetic wave satisfies following condition with metallic particles self structure parameter, can be with the free electron generation coupled resonance of surface of metal particles:

${\mathrm{\&epsiv;}}_m=\frac{L+1}{L}{\mathrm{\&epsiv;}}_D---\left(1\right)$

In the formula, ε _mReal part of permittivity for metal;

ε _DReal part of permittivity for the metallic particles surrounding environment;

L is an integer, and the exponent number of resonance takes place in expression;

So coupled resonance has formed the strong-electromagnetic field of local in surface of metal particles; Also be called as the local surface plasma resonance; Energy of electromagnetic field is divided into two parts during resonance; A part is absorbed by metallic particles self, and another part can be gone out through beyond-the-horizon communication, promptly so-called resonance absorption and resonance scattering; Based on formula (1), the design metallic particles is in solar battery structure, and the electromagnetic scattering that utilizes resonance scattering effect to let resonance produce gets in the photoactive layer, has increased the light intensity that the unit are photoactive layer receives, thereby has improved efficiency of light absorption;

Photoactive layer in the said photoactive layer (5) is the 35nm ultrathin; Can finely must satisfy the requirement of organic semiconducting materials charge carrier diffusion length; Make carrier transport efficient remain on very high level; Resonance scattering through described nanometer metal structure (4) strengthens optical absorption again, makes that the efficiency of light absorption of photoactive layer (5) material is suitable when not only stack pile is big, and the charge carrier that produces can better transport and avoids compound; Thereby improved the battery internal quantum efficiency, promoted battery performance.

2. a kind of organic thin film solar cell that can improve efficiency of light absorption according to claim 1; It is characterized in that: the Ag metallic particles in the said periodicity Ag metal nanoparticle structure is the spheroid of fixed diameter 100nm; This size can make local surface plasma resonance intensity reach maximum and scattering strength at this moment occupies leading much larger than absorption intensity; Reach maximum so get into the electromagnetic intensity of photoactive layer through scattering; Thereby farthest improve the efficiency of light absorption of organic thin film solar cell, this is based under the situation of higher order mode existence, the scattering (C of metallic particles local surface plasma resonance cross section _Sca) and absorb (C _Abs) relation of formula and the two intensity and metal particle size:

$C_{\mathrm{sca}}=C_{\mathrm{sca}1}+{\mathrm{\&Sigma;}}_{i=2}^{\&infin;}{C}_{\mathrm{sca}1}---\left(2\right)$

$C_{\mathrm{abs}}=C_{\mathrm{abs}1}+{\mathrm{\&Sigma;}}_{i=2}^{\&infin;}{C}_{\mathrm{abs}1}---\left(4\right)$

In the formula, D is the metallic particles diameter;

C _ScaAnd C _AbsBe respectively Ag metallic particles cross section total scattering and absorption;

C _Sca1And C _Abs1Be respectively the scattering and the absorption of Ag metallic particles cross section dipole resonance;

and Ag metal particles were cross-sectional view of the high order mode resonance superposition of scattering and absorption values;

At first, the explanation of above-mentioned (3), (5) formula increases with particle size, and the raising of cross section scattering strength is faster, can in resonance, occupy leading gradually along with the diameter increase; And the result of calculation of (2), (4) formula shows; Along with diameter continues to increase; Though the accumulated value of second the high-order resonance in two formula equal signs the right can increase; But first the dipole resonance intensity in equal sign the right can reduce, and in above-mentioned formula (2) to (5), exists the metallic particles diameter of an optimum to make resonance scattering reach maximum, and drawing the optimum metallic particles diameter that can make resonance scattering intensity reach peak value is 100nm; Can strengthen the light absorption of organic solar batteries this moment to greatest extent, raises the efficiency to greatest extent.

3. a kind of organic thin film solar cell that can improve efficiency of light absorption according to claim 2 is characterized in that: 100nm diameter Ag metallic particles is periodic arrangement, and the arrangement cycle is the fixed range of 150-500nm; Interval big or small at this through changing its cycle, regulate the local surface plasma resonance condition of metallic particles, thus can be according to the spectral absorption rule of battery photoactive layer material; And combine solar spectrum energy to distribute; Through the arrangement cycle of design metallic particles, the strongest scattering resonance condition is adjusted to the wavelength band that helps the photoactive layer absorbed most, at utmost improve the spectrum utilance of organic thin film solar cell; This electric resonance that is based between the metallic particles obtains: the metallic particles periodic arrangement; When incident electromagnetic wave shines, the inner polarized electric field that produces of metallic particles, polarized electric field can cause and produce electric resonance between the metal ball; And the energy density between the increase metal ball; The local surface plasma resonance condition changing that causes metallic particles, it is different that different cycle produces the electric resonance effect, but the cycle is too smallly caused serious being in the light; Excessive then do not have a modulation effect, can design in view of the above effective period scope and the method for utilizing the resonance of metallic particles periodic modulation to satisfy the absorbing rule of different photoactive layer organic materials.

4. a kind of organic thin film solar cell that can improve efficiency of light absorption according to claim 1 is characterized in that: said organic thin film solar cell can improve the battery absorbing properties more than 20% at visible light wave range.

5. a kind of organic thin film solar cell that can improve efficiency of light absorption according to claim 1 is characterized in that: said transparent substrates (1) is a glass substrate (11);

Said transparency electrode (2) is the transparent ITO electrode (21) of 150nm for thickness;

Said hole transmission layer (3) is the hole transmission layer (31) of thickness 100nm, and its material is that macromolecular material gathers (3,4-vinyl dioxy thiophene) and gathers (styrene sulfonate) (PEDOT:PSS);

Said nanometer metal structure (4) is an Ag particle cycle array (41);

Said photoactive layer (5) is the photoactive layer (51) of film thickness 35nm, and its photoactive layer material selection gathers (3-hexyl thiophene) (P3HT) and 1-(3-methoxycarbonyl) propyl group-1-phenyl [6,6] C ₆₁(PCBM) blend film (P3HT:PCBM);

Said metal back electrode (6) is Al electrode (61).

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