CN102683440A

CN102683440A - Nanostructured solar cell

Info

Publication number: CN102683440A
Application number: CN2012100519438A
Authority: CN
Inventors: Y·刘
Original assignee: Honeywell International Inc
Current assignee: Honeywell International Inc
Priority date: 2011-01-13
Filing date: 2012-01-13
Publication date: 2012-09-19

Abstract

A solar cell having a nanostructure is provided. The nanostructure may include nanowire electron conductors having a fractal structure with a relatively large surface area. The electron conductors may be loaded with nanoparticle quantum dots for absorbing photons. The dots may be immersed in a carrier or hole conductor, initially being a liquid or gel and then solidifying, for effective immersion and contact with the dots. Electrons may move flow via a load from the electron conductors to the holes of the carrier conductor. The solar cell may be fabricated, for example, with an additive process using roll-to-roll manufacturing.

Description

The solar cell of nano-architecture

The application is the U.S. Patent application No.11/768 of on June 26th, 2007 application, 690, the part of " NANOSTRUCTURED SOLAR CELL (solar cell of nano-architecture) " continues.

The application is the U.S. Patent application No.12/138 of on June 12nd, 2008 application, 114, the part of " NANOSTRUCTURE ENABLED SOLAR CELL ELECTRODE PASSIVATION VIAATOMIC LAYER DEPOSITION (the electrode of solar battery passivation that realizes via the nano-architecture of ald) " continues.

The application is the U.S. Patent application No.12/433 of on April 30th, 2009 application, 560, the part of " ELECTRON COLLECTOR AND ITS APPLICATION IN PHOTOVOLTAICS (electron collector and the application in photovoltage thereof) " continues.

The application is the U.S. Patent application No.12/636 of on December 11st, 2009 application, 402, the part of " QUANTUM DOT SOLAR CELL (quantum dot solar cell) " continues.

The application is the U.S. Patent application No.12/484 of on June 15th, 2009 application, 608, the part of " NANO-STRUCTURED SOLAR CELL (solar cell of nano-architecture) " continues.

Background technology

The disclosure is relevant with electric power equipment, and special relevant with generating equipment.More particularly, the disclosure is relevant with the generating equipment based on the sun.

Related application can comprise:

The U.S. Patent application No.11/768 of on June 26th, 2007 application, 690, " NANOSTRUCTURED SOLAR CELL ", it is combined thus by reference;

The U.S. Patent application No.12/138 of on June 12nd, 2008 application, 114, " NANOSTRUCTURE ENABLED SOLAR CELL ELECTRODE PASSIVATION VIAATOMIC LAYER DEPOSITION ", it is combined thus by reference;

The U.S. Patent application No.12/433 of on April 30th, 2009 application, 560, " ELECTRON COLLECTOR AND ITS APPLICATION IN PHOTOVOLTAICS ", it is combined thus by reference;

The U.S. Patent application No.12/636 of on December 11st, 2009 application, 402, " QUANTUM DOT SOLAR CELL ", it is combined thus by reference; And

The U.S. Patent application No.12/484 of on June 15th, 2009 application, 608, " NANO-STRUCTURED SOLAR CELL ", it is combined thus by reference.

Summary of the invention

The disclosure is the solar cell with millimicro type structure.

Description of drawings

Fig. 1 is the sketch map of nano-architecture solar cell (nanostructure solar cell) and operation thereof;

Fig. 2 is the diagram of the nano-architecture electronic conductor of solar cell;

Fig. 3 is the sketch map that increases progressively (increment) of nano-architecture solar cell structure;

Fig. 4 is the figure of conversion efficiency of solar cell of conversion efficiency and another type of comparison nano-architecture solar cell; And

Fig. 5 illustrates the appearance of the solar cell of nano-architecture.

Embodiment

During decades in the past, use early sun photovoltage (PV) technology or do not demonstrated cost competitiveness to produce cleaning electricity (substitute of the electricity that produces as unclean fossil fuel) based on the solar cell of silicon.Although known technological improvement and ability with expection increases, still can't see solar battery technology will have cost competitiveness in some more ten years for electrical power produces.

Yet, relate to sun PV technology, based on the nano-architecture assembly be intended to significantly to increase conversion efficiency and the disclosure of the corresponding manufacturing process that reduces production costs can allow sun PV in the time range shorter than decades, to become the economically feasible form of renewable alternative energy source.

Through using nano-architecture electronic conductor and millimicro particle (such as quantum dot (QD)) as absorber, this solar cell maximizing sun is to the conversion efficiency of electricity.Can on flexible substrates, make this battery.Make up these assemblies and can produce flexible, low-cost, coarse solar panels, it can adopt simple low temperature technology to prepare.

This solar cell can be in order to the work function/electron affinity of QD uniformity, the millimicro line electronic conductor of the unanimity of coupling solar spectrum, coupling, effectively hole transport medium, leakage/compound reduces or eliminates and the result of the precision engineering that low temperature process is compatible.

This solar cell can comprise, for example, has the electronic conductor based on the millimicro line of high surface area, significant transparency, good flexibility etc.This solar cell can have the QD absorber, has the enhanced absorption cross section, and in quantum dot, has charge multiplication, and can adopt simple additive process (additive process) to process.

As indicated among Fig. 1 and 2, this solar cell can be nano-architecture, and it comprises notable attribute, such as the fractal structure of solid-state hole conductor 16 with nano-architecture electronic conductor 14.Absorber 20 can comprise quantum dot (QD) 15, and it is millimicro particle (nanoparticle), and said millimicro particle can be shaped to by band gap design (band-gap engineered) so that coupling solar radiation frequency spectrum or spectrum are to reach optimized absorption.For the element of given material or compound, the design of the band gap of quantum dot can adopt the geometry designs of said point to realize.The shape that changes quantum dot can influence the band gap of this point.The band gap that can change QD is to maximize the efficient of this solar cell.For example, QD can have tip (point) etc., so that obtain specific energy level to realize specific band gap for circular, oval.

QD with enhanced absorption cross section also can make the energy absorption maximization in the extremely thin film, comprises the possibility that the multi-charge for each high-energy photon 21 produces.In addition, can have the high porosity electronic conductor 14 of nano-architecture, it can provide maximized high surface area so that load the solar absorber 20 of given geometric area and thickness.Absorber element 15 (that is, QD) can be attached to the surface of electronic conductor 14.Branch shape (fractal-like) structure of electronic conductor 14 that possibly it is desirable to have nano-architecture is to realize the optimized charge transfer in the electronic conductor.This electronic conductor 14 possibly look like tree with branch 19 to obtain bigger surface.

In addition; Can there be complementary charge carrier conductor; Such as hole conductor 16, it is in close the contact with the millimicro particle or the QD15 of the electronic conductor 14 that is attached to millimicro porous (nanoporous), thereby makes this conductor 16 provide effective hole to shift and transmission path.It is desirable to, after accomplishing this solar cell manufacturing, have the hole conductor 16 that is in stable and solid state.The material of this hole conductor 16 can be polymer.Can adopt on the flexible substrates of low-cost large scale production method (growth, self assembly, additive process (additive process) such as based on solution are printed and/or spraying) in volume to volume (R2R) production line and form and assemble these projects.

The solar cell (NESC) 10 that this nano-architecture realizes can be operated as indicated among Fig. 1.Can absorb solar energy (photon 21 with energy hv) by quantum dot 15, it can be designed to maximize the absorption of frequency spectrum.Each solar photon 21 can produce one or more pairs of, and each is to comprising electronics (e-) 22 and hole (h+) 23.Can electronics 22 be transferred to have and comprise transparent electron conduction (EC) material (TiO for example ₂, ZnO ...) the millimicro line electronic conductor 14 of structure additives 19, and can collect these electronics 22 from 14 contact plates 12 on it of electronic conductor by transparent negative electrode (anode) 11.Hole 23 can be transferred to transparent organic polymer hole conduction (HC) material 16, and this hole 23 can finally be reflected and protect positive electrode (negative electrode) 27 to collect.Electronic conductive material with conductor 14 of structure 19 should be specific porous nano-architecture with big relatively surface area (as that of millimicro line or nanotube 19), so that more QD 15 is loaded and is exposed to absorb solar energy as much as possible.Fig. 2 shows the diagram of the electronic conductor 14 with millimicro line or nanotube (nanotube) 19.This conductor 14 can similar " tree ", and it has the millimicro line or manages 19, this millimicro line or manage 19 can similar " branch ".One group " tree " with short " branch " can provide the more surface area of given volume, to keep more QD 15.

For effectively electric charge transfer, electronic conductor 14 need be in close the contact with QD 15 with hole conduction material 16.When collected electronics 22 flow through external conductive path 25 and with collected hole 23 compound tenses, can think that the solar energy 21 of incident is converted into electric energy.This path 25 can be to cross over the load that negative electrode 27 is connected with anode 12.

In battery structure 10, use the advantage of millimicro line 19 can comprise the high porosity characteristic, it obtains in the result making absorber 20 load maximization under the situation of high absorption efficiency.In addition, the fractal type structure that has line or manage 19 accrete millimicro electronic conductor 14 can help efficiently the carrier transport path and charge carrier is revealed to minimize.The tree-shaped form of electronic conductor 14 can be provided for the conductive path of efficient especially, the low-resistance of electronics.

A kind of method that is used to make this solar cell 10 can comprise the additive process that the increases progressively stream of the employing structure construction shown in Fig. 3.Can be with flexible substrates 11 beginnings.Can in substrate 11, increase and settle contact layer 12.This layer can be transparent and conduction, and by millimicro line 19 seedings (seeding) to electronic conductor 14.Afterwards, can on contact layer 12, increase and settle the layer 13 of millimicro line electronic conductor 14.This millimicro line 19 can have from tens of diameter and length to hundreds of millimicron (that is, less than 500 millimicrons) and reaches 20 microns.Millimicro line electronic conductor 14 may further include on this millimicro line 19 crust arranged (in such as Fig. 5 illustrated and describe in this article that).QD 15 can be loaded to the maximum horizontal of the free space of electronic conductor and line 14 and 19.Can on

electronic conductor

14 and 19, apply the passivating coating (not shown) reveals to be used for reducing.This passivating coating can be potential barrier with prevent electronics leave electronic conductor 14 and with the hole-recombination of hole conductor 16.Because the potential barrier on the QD can stop the ideal in electronics or hole to move, thus a kind of technology can be used, chemical means for example, but such as providing a kind of hole that allows to pass through the material that does not allow electronics to pass through.

Another kind of technology can realize only covering the open area of the electronic conductor with potential barrier or passivating material and the zone that do not cover QD.Passivation layer on the electronic conductor (such as that illustrate among Fig. 5 and that describe in this article that) can take to be applied to the form of the thin layer of this electronic conductor, thereby make this passivation layer can not block the hole of this electronic conductor.This passivation layer can approach, thus make thickness the millimicron thickness range (～nm) in.In addition, this passivation layer can be conformal (conformal) and the pantostrat on the electronic conductor.Like the conforma layer that defines among this paper is the interface of uneven (morphologically uneven) on the form with another main body, and this another main body has thickness all identical along the everywhere at this interface or much at one.As far as the surface of electronic conductor, this passivation layer can be optionally, thereby makes this passivation layer can apply the surface of this electronic conductor and do not cover this QD.

A kind of method that can make the passivation layer of electronic conductor is ald (ALD).ALD is from limit, continuous surface chemical technology, and it allows the deposition of conformal thin-film.ALD can realize the deposition control of atomic scale.Can obtain atomic layer control through in whole coating processes, keeping precursor to separate (precursor separate) like the so meticulous film growth of every individual layer～0.1 dust.ALD can provide advantage to the deposition of passivation layer, and wherein it can grow it for conformal, free of pinholes and chemically be bonded to the film on electronic conductor surface.Utilize ALD can allow passivation layer to approach, and conformal on every side at the inside and the particle of deep trench, porous substrate, and do not cover QD.This passivation layer can be made up of dielectric oxide or any other suitable compound (such as insulation or semiconductor synthetic).

Efficient is being played the part of important role in possibly and making in the design of photovoltaic device (photovoltaics).Composition that factor can be an electronic conductor that maybe be relevant with efficient.Usually, electronic conductor can come work through being collected in the electronics that produces in the active photovoltage district and they being transferred to anode.

In some barrier-layer cell, the n N-type semiconductor N can be used as electronic conductor.For example, in some barrier-layer cell, electronic conductor can comprise ZnO or TiO ₂Yet these materials possibly limit the efficient of some photovoltaic device.For example, TiO ₂Can have low relatively electron mobility (for example, about 30cm ²About/V/s).The transmission of this electronics that possibly limit or slow down, it possibly cause electronics and so can't be transferred to anode and to be transferred to the possibility of external circuit as electricity with hole-recombination.Therefore, by TiO ₂The electronic conductor of processing can be described to have low collection or collecting efficiency.In another example, the electronic conductor of being processed by ZnO can have the low relatively density of states (density of state) in the at of its conduction band (conduction band).This electron transfer rate to electronic conductor that may slow down from active photovoltage district.Therefore, the electronic conductor of being processed by ZnO can be described to have low relatively electron injection efficiency.Low collection efficiency in the barrier-layer cell and low injection efficiency both can cause lower incident photon to electric charge carrier efficient and/or power conversion efficiency.

Usually, disclosed photovoltaic device of this paper and/or barrier-layer cell can be made more efficient through the for example collection efficiency of use increase battery and/or the electronic conductor of injection efficiency.The method that this paper is disclosed to be used to make photovoltaic device and/or barrier-layer cell can be used for making photovoltaic device more efficiently.

In the discussion of the manufacturing solar cell 10 that provides relatively with Fig. 3, it has stated that electronic conductor 14 can be included in the crust on the millimicro line 19.Electronic conductor 14 can comprise the nuclear (core) processed by the material with high relatively electron mobility or the array of millimicro line 19.In some cases, millimicro line 19 electron mobility that can have an electron mobility that is higher than crust (for example, is higher than TiO ₂, it has about 30cm ²The electron mobility of/V/s).In some cases, as required, the electron mobility of millimicro line 19 can be greater than 30cm ²/ V/s, greater than 100cm ²/ V/s, greater than 200cm ²/ V/s or higher.In some cases, millimicro line 19 can comprise ZnO, and it possibly have about 200cm ²Electron mobility about/V/s.

The crust that on millimicro line 19, extends can comprise following material, and this material has the high relatively density of states in the at of its conduction band.In one example, for crust, possibly it is desirable to have the density of states (for example, being higher than the density of states of ZnO) of the density of states that is higher than millimicro line 19, but this is not to need.In some cases, this outer micromicro comprises TiO ₂, it has the conduction band of the about 0.2eV higher than the conduction band of ZnO.TiO ₂Can have by Ti ⁴⁺The conduction band that forms of empty 3d track (orbital).On the contrary, ZnO can have by Zn ²⁺The conduction band that forms of empty 4s track.Therefore, TiO ₂In effective electron mass can be about 10 _Me, and it can be about 0.3 in ZnO _MeWith in ZnO, compare, this can cause at TiO ₂In higher attitude bulk density (bulk density of state) (for example, high approximately 189 times).Therefore, at TiO ₂The electronics of collecting from QD in the crust can more easily flow down to the conduction band of ZnO millimicro line 19, and may not easily cross over this energy barrier and jump back.

The deployment of the crust on the millimicro line 19 can be included in the growth of the crust on the millimicro line.This can comprise liquid deposition, although can also utilize sputter and/or evaporation as required.In one example, can in deionized water, dissolve ammonium hexa-fluorotitanate and mix with boric acid to form TiO ₂Crust solution.Substrate 11 (having the millimicro line 19 that forms above that) can be immersed in this TiO ₂In the crust solution, thereby make and on this millimicro linear array, form crust.

Fig. 5 illustrates the appearance of the solar cell of nano-architecture.Fig. 5 is highly schematic and not drawn on scale.Electronic conductor 114 shows similar form with tree of branch.The millimicro line 119 of various sizes forms " trunk " and " branch " of tree, shows topological structure fractal or the branch shape.Schematically zoomed-in view shows further CONSTRUCTED SPECIFICATION.Can be disposed on the millimicro line 119 like crust 130 described herein.Passivation or barrier layer 140 and quantum dot 150 can be disposed between the millimicro line 119 of hole conductor 160 and electronic conductor 114.The potential barrier of this passivation layer 140 can be used as the purpose that stops free key (dangling bond), and it can reduce or reduce the possible path of charge recombination.Such configuration also can be used for providing physical barrier, its keep in electronic conductor 114 electric charge and the hole in the hole conductor 160 (for example, electron-hole pair) be separated from each other.

In the solar cell (NESC) that nano-architecture realizes, one of key issue of possible limiting performance is the charge carrier loss that causes owing to the charge recombination in the generation of the surface of electronic conductor 114 and hole conductor 160.Compound electric charge can not produce any photoelectric current, and therefore can not contribute to some extent solar battery efficiency.Such recombination losses possibly be significant potentially, because there is potential high surface area, it maybe not can be covered by the quantum dot between two porous assemblies that connect each other 150.The design of NESC possibly require the maximum on the surface of electronic conductor to be covered by quantum dot 150.Even the sizable part at electronic conductor 114 is used under the situation of quantum dot 150 coverings,, then exist wherein said point 150 can directly be exposed to the considerable part of hole conductor 160 if it were not for passivation layer 140.Through between electronic conductor 114 and hole conductor 160, setting up such passivation layer 140, reduced charge recombination significantly, it has increased the efficient of the solar cell of this nano-architecture realization again.

Yet, in some cases, if they compound fast of the transfer ratio in electronics and hole must not need passivating coating or potential barrier so.

Can hole+conductor 16 (160) be applied to said parts with the form of liquid or gel.This liquid or gel rubber material 16 possibly in fact quite fully immerse or infiltrate millimicro particle QD 15.In case after being applied in, hole conductor 16 materials of this liquid or gel form can solidify to reach structural rigidity and sealing.Top reflector with contact interconnection (negative electrode) 27 and (one or more) protective layer 17 (Fig. 1) and can be connected to hole conductor 16 and be added into said parts.Layer 17 or negative electrode 27 can comprise ARC.Layer 17 alternately is one deck with negative electrode 27.The gross thickness 18 (Fig. 3) of this solar cell 10 parts can be less than 1 millimeter.

Solar cell (NESC) 10 manufacturing process that nano-architecture realizes can suitably relate to low-cost volume to volume manufacturing.This technology can relate to effective use of minimal amount of material and material, for example QD＜1mg/m ²Manufacturing or preparation technology's expectation aspect can comprise the low temperature setting, and the needs that lack against vacuum and super-clean environment.This technology can with spraying/printing technology of using flexible substrates 11 and being used to load QD 15 and polymer conductor (that is, conductor 16) compatibility mutually.The technology (leverage) capable of using that is used to make this battery 10 is used to make display (for example LCD) and the manufacturing infrastructure of exploitation, and it relates to conductive, transparent oxide or film and ARC.

Point out as this paper; In battery 10, use quantum dot 15 can allow the band gap design to mate various solar spectrums; Be provided for the remarkable big absorption cross-section of maximal efficiency; And produce potential charge multiplication so that the individual layer battery conversion efficiency is increased by 30%, as the Figure 30 among Fig. 4 is indicated.The conversion efficiency (percentage) that the figure shows unijunction (semiconductor) solar cell is to band gap (eV) (shown in curve 31), and the conversion efficiency (percentage) of the example of this unijunction quantum dot solar cell 10 (having charge multiplication) is to band gap (eV) (shown in curve 32).

This nano-architecture solar cell 10 can provide significant relatively power.Solar cell 10 can have the conversion efficiency of the high sun to electricity.This battery can be flexible, the light weight and the highly portable energy, and it has at 20-40mW/cm ²Power output performance in the scope.Battery 10 can provide NSC 40mW/cm down in a solar time (one-sun) ²Continuous power.A cm ²Battery can provide power enough for the operation of radio communication and unserviced ground transaucer.One to two cm ²Battery can be small-sized atomic clock power supply.Two cm ²Battery can be whenever analyzed minitype gas analyzer (MGA) power supply that once (has the 1J/ analysis purpose) at a distance from 25 seconds.PC on knee can self-powered under the sun.(battery 10) the flexible solar plate that has covered " the electric power helmet " can be less than in 30 minutes to charging mobile phone battery.

The electronic applications equipment (for example less battery and charging) of the light weight of capable of using solar energy to electrical transducer of military applications to be used for the soldier.Compare with the power supply of (out-in-the-field) outside other similar this areas of satisfying similar power requirement, this solar cell or transducer 10 can be unserviced ground transaucer more lasting power and longer life-span are provided.The nano-architecture of this solar cell 10 can provide low cost and high efficiency to the continued power and the integrated energy solution of the miniaturized system that is used for the soldier.

In this manual, although in another way or tense state, some problem possibly have the hypothesis or the prophesy character.

Although the disclosure has been directed against at least one illustrated examples and has been described, when reading this specification, to those skilled in the art, a lot of distortion will become obvious with modification.Therefore purpose is: appended claims is being considered distortion and the modification of being explained under the situation of prior art to comprise that all are so as far as possible widely.

Claims

1. solar cell comprises:

Electronic conductor with nano-architecture; Wherein said nano-architecture has fractal structure; Wherein said in addition electronic conductor be constructed to similar tree with branch with more surface area that given volume is provided so that keep more quantum dot, and effective carrier transport path to be provided and Carrier Leakage is minimized;

Crust, it is set on the said nano-architecture of said electronic conductor;

Absorber, it is placed on the said crust; And

Hole conductor, it contacts with said absorber; And

Wherein said nano-architecture comprises having greater than 30cm ²The material of the electron mobility of/V/s, and said crust comprises the material of the density of states of the density of states with the material that is higher than said nano-architecture.

2. the described battery of claim 1, wherein:

Said absorber comprises the millimicro particle;

Said battery also comprises passivation layer, and said passivation layer is disposed on the said nano-architecture between the said millimicro particle, rather than between said millimicro particle and said nano-architecture; And

Said nano-architecture be porous so that maximum surface area is provided.

3. the described battery of claim 2, wherein:

Said millimicro particle is a quantum dot; And

Said quantum dot is designed the absorption with the special spectrum that is used for light by band gap.

4. the described battery of claim 1, further wherein:

Said nano-architecture is connected to flexible and/or transparent substrate;

Said hole conductor is connected to the contact;

Said substrate is an anode; And

Said contact is a negative electrode.

5. the described system of claim 1, wherein:

Said hole conductor is a polymer; And

The thickness of said solar cell is less than 1 millimeter.

6. one kind is used for the method that solar energy to electric energy is changed, and comprising:

One or more millimicro porous electronic conductors are provided, and wherein said millimicro porous electronic conductor has fractal structure, and wherein said in addition electronic conductor is constructed to similar tree with branch;

Adopt quantum dot that said millimicro porous electronic conductor is loaded to form absorber;

Arranging passivation layer on one or more millimicro porous electronic conductors between the said quantum dot rather than between said quantum dot and said millimicro porous electronic conductor;

The hole conductor that contacts with said absorber is provided; And

To said absorber photon is provided; And

Wherein:

Said photon is absorbed by said quantum dot;

Said photon produces the right of electronics and hole;

Said electronics moves to said millimicro porous electronic conductor; And

Said hole moves to said hole conductor.

7. the described method of claim 6 also comprises:

Anode is connected to said electronic conductor; And

Negative electrode is connected to said hole conductor; And

Wherein:

Thereby be connected conductive path with said negative electrode and make said electronics move through load with the said hole-recombination of said hole conductor the time from said electronic conductor when crossing over said anode, said photon is converted into electric energy; And

Said path comprises at least a portion with the electronic equipment that is powered.

8. the described method of claim 7, wherein:

Said quantum dot is designed to mate the spectrum as the sunlight in the source of said photon by band gap; And

In the volume to volume production technology, adopt large scale production method on flexible substrates, to make the parts that comprise the said anode, electronic conductor, absorber, hole conductor and the negative electrode that are used for the conversion of solar energy to electric energy.

9. solar-energy conversion systems comprises:

First conductor;

Be connected to a plurality of millimicro lines of said first conductor, the branch of the similar tree with fractal type structure of wherein said millimicro line;

A plurality of millimicro particles, it is loaded on said a plurality of millimicro line; And

The charge carrier conductor, it contacts with said millimicro particle.

10. the described system of claim 9 also comprises:

Passivation layer, it is disposed on the said millimicro line between the said millimicro particle and not between said millimicro particle and said millimicro line; And said millimicro particle is used to absorb photon; And

Wherein:

Each photon is split into electronics and hole when absorbing;

Said electronics goes to said millimicro line;

Said charge carrier conductor is gone in said hole;

Said millimicro line is made by transparent conductive material;

Said charge carrier conductor comprises transparent organic polymer hole conduction material; And

The sub-point of said millimicro particle binding capacity, said quantum dot is designed to mate the spectrum as the sunlight in the source of just absorbed photon by band gap.