CN206595272U

CN206595272U - GaInP/GaAs/Ge three-joint solar cells

Info

Publication number: CN206595272U
Application number: CN201621476419.5U
Authority: CN
Inventors: 王颖
Original assignee: Shaanxi Xueqian Normal University
Current assignee: Shaanxi Xueqian Normal University
Priority date: 2016-12-30
Filing date: 2016-12-30
Publication date: 2017-10-27
Anticipated expiration: 2026-12-30

Abstract

The utility model is related to a kind of GaInP/GaAs/Ge three-joint solar cells, including：Si substrate layers, stack gradually Ge epitaxial layers, bottom battery layers, middle battery layers, top battery layers, contact layer and the reflectance coating on the Si substrate layers；Ge is LRC crystal in the Ge epitaxial layers；The bottom battery layers include Ge bases, Ge launch sites, GaAs Window layers；The middle battery layers include cell back field, GaAs bases, GaAs launch sites, Ge in the first GaAs tunnel knots, GaAs_0.51In_0.49P Window layers, the top battery layers include the 2nd GaAs tunnel knots, Ge_0.51In_0.49P tops cell back field, Ge_0.51In_0.49P bases, Ge_0.51In_0.49P launch sites and Al_0.53In_0.47P Window layers.Ge epitaxial layers described in the utility model is LRC crystal, can effectively reduce the dislocation density of Ge/Si substrates；Meanwhile, also more foregoing common methods are thinner for Ge film thicknesses on Si substrates, so as to be more beneficial for the transmission of light.The utility model, which provides the GaInP/GaAs/Ge three-joint solar cells, to obtain higher electricity conversion.

Description

GaInP/GaAs/Ge three-joint solar cells

Technical field

The utility model belongs to technical field of solar batteries, and in particular to a kind of GaInP/GaAs/Ge three-joint solars Battery.

Background technology

Solar energy is as a kind of important reproducible clean energy resource, and to alleviating, increasingly serious energy crisis and environment are dirty It is infected with highly important meaning.Solar cell is the technical principle of the opto-electronic conversion using semiconductor, and solar energy source is straight Switch through the technology for changing electric energy into.Compared with other energy, solar cell, which generates electricity, has advantages below：Without exhausted dangerous；It is definitely dry Only；Do not limited by resource distribution region；Can nearby it be generated electricity at electricity consumption；Energy quality is high；The time for obtaining energy cost is short.

At present, the laboratory record efficiency of unijunction GaAs hull cells is 26.1%, the value already close to theoretical limit, from From the perspective of solar energy utilization ratio or than relatively low.In order to develop high performance solar batteries technology, it is necessary to break through limitation unijunction The main constraint of battery efficiency.And a kind of important method for improving battery efficiency is using many knot (multi-junction) laminations Structure, it is common practice that be sequentially connected in series the different two or more sub- batteries of band gap together by band gap size.Work as sunshine When incident, high-energy photons are first absorbed by the big sub- battery of band gap, and subsequent energy photons are inhaled by the narrower sub- battery of band gap again Receive, the rest may be inferred.Its essence divide into several sections equivalent to solar spectrum, each sub- battery absorb with its band gap it is immediate that Duan Guang.The absorptivity to low energy end spectrum had so both been added, the energy loss of high-energy photons is reduced again, battery is improved The advantage of efficiency is apparent.Many compounds of group solar cells of knot III-V are due to higher photoelectric transformation efficiency, Key content as high performance solar batteries technical research.

At present, many race's solar cells of knot III-V are more is used as substrate using GaAs, Ge and Si base Ge films.Wherein, GaAs and Ge substrate prices compare Si substrates costliness, and mechanical performance and heat endurance are also not so good as Si substrates.Although Si base Ge substrates have Si concurrently Ge films are prepared in the advantage of substrate and Ge films, but Si substrates still has technical problem to need solution.For being prepared on Si substrates For two methods of the common content gradually variational SiGe buffer layer techniques of Ge films and hypo-hyperthermia two-step growth method, the former technique More complicated, cushion is thicker；The latter still can not solve the appearance of a large amount of dislocations in Ge epitaxial layers, and this causes solar cell Photoelectric transformation efficiency is substantially reduced.

Therefore, high-quality, high-photoelectric transformation efficiency multijunction solar cell how is developed most important.

Utility model content

The purpose of this utility model is there is provided a kind of GaInP/GaAs/Ge three-joint solar cells, the GaInP/ Again prepared by crystallization (Laser Re-Crystallization, abbreviation LRC) technique using laser for GaAs/Ge three-joint solar cells Ge/Si substrates, with relatively low dislocation density, with high-quality photoelectric transformation efficiency.

One embodiment of the present utility model provides a kind of GaInP/GaAs/Ge three-joint solar cells, including：Si is served as a contrast Bottom, stack gradually Ge epitaxial layers on the Si substrate layers, bottom battery layers, middle battery layers, top battery layers, contact layer and Reflectance coating；

Wherein, Ge is LRC crystal in the Ge epitaxial layers；

Wherein, the bottom battery layers include stacking gradually in the Ge bases on the Ge epitaxial layers, Ge launch sites, GaAs windows Mouth layer；The middle battery layers include stacking gradually the battery in the first GaAs tunnel knots in the GaAs Window layers, GaAs and carried on the back Field, GaAs bases, GaAs launch sites, Ge_0.51In_0.49P Window layers, the top battery layers include stacking gradually in described Ge_0.51In_0.49The 2nd GaAs tunnel knots, Ge in P Window layers_0.51In_0.49P tops cell back field, Ge_0.51In_0.49P bases, Ge_0.51In_0.49P launch sites and Al_0.53In_0.47P Window layers.

In one embodiment of the present utility model, Ge bases thickness is 500nm；Ge launch sites thickness is 300nm。

In one embodiment of the present utility model, GaAs bases thickness is 2um；GaAs launch sites thickness is 0.5um。

In one embodiment of the present utility model, the Ge_0.51In_0.49P bases thickness is 500nm；It is described Ge_0.51In_0.49P launch sites thickness is 100nm.

In one embodiment of the present utility model, the LRC crystal is that crystallization process prepares generation again using laser.

In one embodiment of the present utility model, the Si substrate layers thickness is 2 μm.

In one embodiment of the present utility model, the Ge epitaxy layer thickness is 500nm.

In one embodiment of the present utility model, the contact layer material is GaAs, and thickness is 0.5um；

In one embodiment of the present utility model, the reflective film material is Si₃N₄, thickness is 100nm.

In one embodiment of the present utility model, the GaInP/GaAs/Ge three-joint solar cells also include contact Electrode, the contact electrode includes being located at the negative electrode under Si substrate layers and the positive electrode on the contact layer.

Compared with prior art, this tries out new have the advantages that：

1st, this it is on probation it is new use silicon materials as substrate, reduce the manufacturing cost of solar cell；

2nd, this new Ge film thickness obtained by continuous laser auxiliary crystallization Ge/Si substrates on probation is less than conventional method Ge film thicknesses on Si substrates, are more beneficial for light enhancing transmission, and then can improve solar cell properties；

3rd, this it is on probation it is new the dislocation density of Ge/Si substrates can effectively be reduced by continuous laser auxiliary crystallization, based on Ge/ The GaInP/GaAs/Ge three-joint solar cells of Si substrates can effectively reduce recombination current density, so as to obtain higher light Electric transformation efficiency.

Brief description of the drawings

A kind of GaInP/GaAs/Ge three-joint solar cells structural representation that Fig. 1 provides for the utility model embodiment；

A kind of schematic diagram for LRC techniques that Fig. 2 provides for the utility model embodiment；

Phase transition temperature relation signal in a kind of thin film actuated light irradiation process that Fig. 3 provides for the utility model embodiment Figure；

A kind of FEM Numerical Simulation of the technique for Ge/Si backing materials that Fig. 4 provides for the utility model embodiment shows It is intended to；

A kind of continuous LRC technological effects schematic diagram that Fig. 5 provides for the utility model embodiment；And

Fig. 6 a- Fig. 6 p are prepared for a kind of GaInP/GaAs/Ge three-joint solar cells that the utility model embodiment is provided Process schematic representation.

Embodiment

Further detailed description, but embodiment party of the present utility model are to the utility model with reference to specific embodiment Formula not limited to this.

Embodiment one

Refer to Fig. 1, a kind of GaInP/GaAs/Ge three-joint solar cells that Fig. 1 provides for the utility model embodiment Structural representation；The GaInP/GaAs/Ge three-joint solar cells include：Si substrate layers 01, are stacked gradually in Si linings Ge epitaxial layers 02, bottom battery layers 03, middle battery layers 04, top battery layers 05, contact layer 06 and reflectance coating 07 on bottom；

Wherein, Ge is LRC crystal in the Ge epitaxial layers 02；

Wherein, the bottom battery layers 03 include stacking gradually in the Ge bases 031 on the Ge epitaxial layers 02, Ge launch sites 032nd, GaAs Window layers 033；The middle battery layers 04 include stacking gradually in the first GaAs tunnels in the GaAs Window layers 033 Cell back field 042, GaAs bases 043, GaAs launch sites 044, Ge in road knot 041, GaAs_0.51In_0.49It is P Window layers 045, described Top battery layers 05 include stacking gradually in the Ge_0.51In_0.49The 2nd GaAs tunnel knots 051 in P Window layers 045, Ge_0.51In_0.49P tops cell back field 052, Ge_0.51In_0.49P bases 053, Ge_0.51In_0.49P launch sites 054 and Al_0.53In_0.47P Window layer 055.

Wherein, the thickness of Ge bases 031 is 500nm；The thickness of Ge launch sites 032 is 300nm.

Wherein, the thickness of GaAs bases 043 is 2um；The thickness of GaAs launch sites 044 is 0.5um.

Wherein, the Ge_0.51In_0.49The thickness of P bases 053 is 500nm；The Ge_0.51In_0.49The thickness of P launch sites 054 is 100nm。

Preferably, the LRC crystal is that crystallization process prepares generation again using laser.

Wherein, laser power used is 6.1kW/m, and laser traverse speed is 400mm/min, and crystallization causes continuous laser again The dislocation rate of the Ge epitaxial layers 02 is substantially reduced.

Preferably, the thickness of Si substrate layers 01 is 2 μm.

Preferably, the thickness of Ge epitaxial layers 02 is 500nm.

Wherein, the Ge epitaxial layers 02 grow to be formed by magnetron sputtering method, can improve deposition rate, and the matter of film Measure, it is suitable for mass production.

Preferably, the material of contact layer 06 is GaAs, and thickness is 0.5um.

Preferably, the material of reflectance coating 07 is Si₃N₄, thickness is 100nm.

Preferably, the GaInP/GaAs/Ge three-joint solar cells also include contact electrode 08, the contact electrode 08 Including the negative electrode 081 under Si substrate layers 01 and the positive electrode 082 on the contact layer 06.

Refer to Fig. 2, a kind of schematic diagram for LRC techniques that Fig. 2 provides for the utility model embodiment.First use magnetron sputtering Technique through two-step method forms thin with chemical vapor deposition (Chemical Vapor Deposition, abbreviation CVD) technique Ge epitaxial layers, then with the dislocation mismatch between continuous LRC laterally release Ge and Si, so as to reduce in epitaxial layer due to lattice mismatch Caused dislocation, prepares Ge/Si substrates best in quality.

Refer to the temperature phase in Fig. 3, a kind of thin film actuated light irradiation process that Fig. 3 provides for the utility model embodiment Become relation schematic diagram；Wherein, LRC principle is that material surface transient heating is allowed to melt crystallization using the high-energy of laser, Its essence is the process of thermal induced phase transition, and this point also has essential distinction with traditional laser thermal anneal.Therefore, LRC can be regarded as Laser is melted illuminated film by fuel factor to the fuel factor of film, i.e. laser, and knot is allowed to cool in the shorter time Brilliant process.LRC techniques are broadly divided into the three below stage：

1) interaction stage of laser and material.This stage material absorbing laser energy is changed into heat energy, reaches fusing State.During high-order harmonics spectrum, electric property, optical property, constructional aspect of material etc. change.

2) the heat transfer stage of material.According to thermodynamics basic law, laser action in will occur on material conduction, it is right Three kinds of heat transfer types of stream and radiation, now firing rate is fast, and thermograde is big.

3) mass transfer stage of the material under laser action.Mass transfer, i.e. material are moved to separately from a certain position in space or space The phenomenon at one position.In this stage, the particle setting in motion of energy is obtained through laser emission.There are two kinds of forms in mass transfer：Diffusion Mass transfer and convective mass transfer.What diffusion mass transfer was represented is the microscopic motion of atom or molecule；Convective mass transfer is then the macroscopic view fortune of fluid It is dynamic.Exemplified by melting crystallization mechanism completely, the temperature variations of laser crystallization rear film again are as shown in Figure 3.

Using laser, crystallization LRC technologies auxiliary prepares high-quality empty Ge substrates again, it is desirable to Ge layers of temperature of void under laser action At least up to fusing point, and close proximity to scorification point, reach the nearly complete molten condition of preferable crystallization, it is ensured that Ge crystal grain it is follow-up complete U.S.'s crystallization.Meanwhile, the Si substrate layers below epitaxial layer can not reach fusing point, it is ensured that LRC does not produce influence on substrate.Therefore, It is determined that rational LRC techniques related process parameters (such as laser power density, translational speed), control epitaxial layer Temperature Distribution, It will be the key of the technique success or failure.Fig. 4 is referred to, a kind of Ge/Si backing materials that Fig. 4 provides for the utility model embodiment The FEM Numerical Simulation schematic diagram of technique.In figure, ordinate represents Ge/Si system thickness, Ge epitaxy layer thickness 500nm's Laser power is used on Ge/Si substrates for 6.1kW/m, laser traverse speed can realize that Ge melts for 400mm/min process conditions Change and crystallize and Si does not melt.

Fig. 5 is referred to, Fig. 5 for a kind of continuous laser that the utility model embodiment is provided illustrate again by crystallization process effect Figure.Laser is pointed into sample stage by total reflection prism, and by convex lens focus to sample, so as to prevent in thermal histories Liquid after middle film melts is affected by gravity and flowed the influence produced to crystallization.Laser again crystallization when, stepper motor drive Sample stage is moved, and is often moved to a position and is carried out a laser irradiation, the position is turned into the blockage with high-energy, and Stop laser irradiation afterwards, sample stage is further continued for laser irradiation when being moved to the next position.So circulation causes laser to irradiate successively To whole film surface, continuous laser crystallization process again is so far completed.

In addition, it is necessary to emphasize, LRC techniques of the present utility model and laser annealing (laser annealing) Technique has significant difference.Laser annealing technique, belongs to thermal anneal process category.It uses laser as thermal source, only to semiconductor Heated, phase transition process is not produced.And the utility model laser is again in crystallization process processing procedure, semi-conducting material meeting Occur phase transformation twice -- melt the solid-phase crystallization again that liquefies then.Thus, technique both this has significant difference in itself.

The Ge crystal that the utility model GaInP/GaAs/Ge three-joint solar cells are prepared using LRC techniques is used as extension Layer, with high-quality Ge/Si substrates, relatively low dislocation density, and Ge epitaxial layers are very thin, beneficial to the transmission of light, with high device Part performance.

Embodiment two

It refer to GaInP/s of Fig. 6 a- Fig. 6 p, Fig. 6 a- Fig. 6 p for a kind of Ge/Si substrates of this new embodiment on probation The preparation method of GaAs/Ge three-joint solar cells, on the basis of above-described embodiment, the present embodiment will be in more detail to this New technological process is tried out to be introduced.This method includes：

S101, as shown in Figure 6 a, it is original material to choose the monocrystalline silicon Si substrate slices 001 that thickness is 2 μm；

S102, as shown in Figure 6 b, one layer is grown using magnetron sputtering method on the Si substrates 001 with two-step process The formation Ge/Si substrates of Ge epitaxial layers 002 thick 500nm, deposit film, deposition rate is high, and film by magnetron sputtering method Quality it is good, it is suitable for mass production；

S103, as fig. 6 c, using CVD techniques, 150nm SiO is deposited in the Ge/Si substrate surfaces₂Oxide layer 003；

S104,500K is first heated the material on the basis of Fig. 6 c, SiO is then carried by LRC techniques crystallization₂Oxidation The Ge epitaxial layers 002 of layer 003, wherein laser power are 6.1kW/m, and laser traverse speed is 400mm/min, then makes material Expect natural cooling.Continuous laser crystallization causes the dislocation rate of Ge epitaxial layers 002 to substantially reduce；

S105, as shown in fig 6d, the SiO in Fig. 6 c is etched using dry etch process₂Oxide layer 003, obtains height The Ge/Si substrates of quality.

It is prepared by S106, bottom battery layers；Here is the experimental detail for preparing different solar cell layers：The preparation of GaAs materials TMGa is used for group III source, ASH₃For group V source, its 500-600 DEG C of GaAs individual layer doped growings temperature.The p-type layer of GaAs materials Dopant selects C, and n-layer dopant selects Se.Ge_0.51In_0.49The preparation of P materials is with TMGa, TMIn and PH₃For source, reative cell 60 Torrs of pressure, 80-120 revs/min of substrate pallet rotating speed, wherein 650-680 DEG C of growth parameter(s), H₂Se is used as GalnP₂N-type doping Agent, using DEZn as InGaP p-type dopant.

S1061, as shown in fig 6e, prepares the base and launch site of bottom battery.Using MBE techniques, extension is given birth at 500 DEG C Ge materials thick long 500nm and carry out p-type doping to it as the base 004 of bottom battery, and doping concentration is 2 × 10¹⁷cm^-3； Then thick extension 300nm Ge materials, as the launch site 005 of bottom battery, and carry out n-type doping to it again, and doping concentration is 1 ×10¹⁸cm^-3。

S1062, as shown in Figure 6 f, utilizes metallo-organic compound chemical gaseous phase deposition (Metal-organic Chemical Vapor Deposition, abbreviation MOCVD) technique, deposition thickness is used as bottom for 200nm GaAs at 600 DEG C The Window layer 006 of battery, and n-type doping, concentration about 1 × 10 are carried out to Window layer by thermal diffusion technology¹⁸cm^-3。

It is prepared by S107, middle battery layers；

S1071, as shown in figure 6g, prepares the GaAs tunnel knots of bottom battery and middle battery.The GaAs tunnel knots reative cell 60 Torrs of pressure, 100 revs/min of graphite substrate support rotary speed.First grow n-type doping layer 007, doping concentration be 1 × 10¹⁹cm^-3, 550 DEG C of growth temperature, using bradyauxesis, growth rate is 5nm/min, thickness about 15nm；Then 600 are warming up to DEG C growing P-type doped layer 008, doping concentration is 5 × 10¹⁹cm^-3, growth rate is then 10nm/min, thickness about 15nm.

S1072, as shown in figure 6h, using MOCVD techniques, deposition thickness is 100nm GaAs material conducts at 600 DEG C Cell back field 009 in preparation, and p-type doping is carried out to back surface field layer, concentration is 5 × 10¹⁸cm^-3。

S1073, as shown in Fig. 6 i, using MOCVD techniques, the base 010 of battery and transmitting in GaAs are deposited at 600 DEG C Area 011.Base thickness about 2um, n-type doping, concentration is 1 × 10¹⁷cm^-3, launch site thickness about 0.5um, n-type doping, concentration is 1×10¹⁸cm^-3。

S1074, as shown in Fig. 6 j, using MOCVD techniques, deposition thickness is 100nm Ge at 650 DEG C_0.51In_0.49P makees For the Window layer 012 of middle battery, and n-type doping, concentration about 2 × 10 are carried out to Window layer by thermal diffusion technology¹⁸cm^-3。

It is prepared by S108, top battery layers；

S1081, as shown in Fig. 6 k, prepare the GaAs tunnel knots of top battery and middle battery.N-type doping layer 013 is grown first, Doping concentration is 1 × 10¹⁹cm^-3, 550 DEG C of growth temperature, thickness about 15nm；Then 600 DEG C of growing P-type doped layers are warming up to 014, doping concentration is 5 × 10¹⁹cm^-3, thickness about 15nm.

S1082, as shown in Fig. 6 l, utilize MOCVD techniques, deposit Ga_0.51In_0.49P materials push up cell back field as preparation 015.Back surface field layer thickness is 100nm, is adulterated using p-type, and concentration is 1 × 10¹⁸cm^-3。

S1083, as shown in Fig. 6 m, utilize MOCVD techniques, deposit Ga_0.51In_0.49P materials are used as the base 016 for pushing up battery With launch site 017.Base thickness about 500nm, n-type doping, concentration is 1 × 10¹⁷cm^-3, launch site thickness about 100nm, p-type mixes Miscellaneous, concentration is 1 × 10¹⁸cm^-3。

S1084, as shown in Fig. 6 n, deposit Al_0.53In_0.47P carries out N as the Window layer 018 for pushing up battery, and to Window layer Type adulterates, concentration about 2 × 10¹⁸cm^-3, window layer thickness is 30nm.

S108, preparation GaAs contact layers and reflectance coating.As shown in Fig. 6 o, GaAs thick epitaxial growth 0.5um is used as contact Layer 019, and it is 1 × 10 that concentration is carried out to GaAs¹⁹cm^-3N-type doping, and use plasma-reinforced chemical vapor deposition technology The thick Si of 100nm are deposited at 250 DEG C₃N₄It is used as reflectance coating 020.

S109, preparation contact electrode.

Back electrode is deposited first, continuously plates back electrode 021 successively in evaporation coating machine during plated film, back electrode has been deposited Afterwards, in N₂It is placed under protection in sintering furnace and 20min is sintered with 380 DEG C of temperature, strengthens the combination of back electrode and silicon, and with phase Positive electrode 022 is prepared with mode, as shown in Fig. 6 p.

In summary, specific case used herein is to a kind of knot sun of GaInP/GaAs/Ge tri- of the present utility model Energy battery is set forth, and the explanation of above example is only intended to help and understands that method of the present utility model and its core are thought Think；Simultaneously for those of ordinary skill in the art, according to thought of the present utility model, in embodiment and model is applied Place and will change, in summary, this specification content should not be construed as to limitation of the present utility model, and this practicality is new The protection domain of type should be defined by appended claim.

Claims

1. a kind of GaInP/GaAs/Ge three-joint solar cells, it is characterised in that including：Si substrate layers, are stacked gradually in described Ge epitaxial layers, bottom battery layers, middle battery layers, top battery layers, contact layer and reflectance coating on Si substrate layers；

Wherein, Ge is LRC crystal in the Ge epitaxial layers；

Wherein, the bottom battery layers include stacking gradually in the Ge bases on the Ge epitaxial layers, Ge launch sites, GaAs windows Layer；The middle battery layers include stacking gradually in the first GaAs tunnel knots in the GaAs Window layers, GaAs cell back field, GaAs bases, GaAs launch sites, Ge_0.51In_0.49P Window layers, the top battery layers include stacking gradually in described Ge_0.51In_0.49The 2nd GaAs tunnel knots, Ge in P Window layers_0.51In_0.49P tops cell back field, Ge_0.51In_0.49P bases, Ge_0.51In_0.49P launch sites and Al_0.53In_0.47P Window layers.

2. solar cell as claimed in claim 1, it is characterised in that Ge bases thickness is 500nm；The Ge transmittings Area's thickness is 300nm.

3. solar cell as claimed in claim 1, it is characterised in that GaAs bases thickness is 2um；The GaAs hairs Area's thickness is penetrated for 0.5um.

4. solar cell as claimed in claim 1, it is characterised in that the Ge_0.51In_0.49P bases thickness is 500nm；Institute State Ge_0.51In_0.49P launch sites thickness is 100nm.

5. solar cell as claimed in claim 1, it is characterised in that the LRC crystal is to use laser crystallization process again Prepare generation.

6. solar cell as claimed in claim 1, it is characterised in that the Si substrate layers thickness is 2 μm.

7. solar cell as claimed in claim 1, it is characterised in that the Ge epitaxy layer thickness is 500nm.

8. solar cell as claimed in claim 1, it is characterised in that the contact layer material is GaAs, thickness is 0.5um。

9. solar cell as claimed in claim 1, the reflective film material is Si₃N₄, thickness is 100nm.

10. solar cell as claimed in claim 1, it is characterised in that the GaInP/GaAs/Ge three-joint solar cells Also include contact electrode, the contact electrode include be located at Si substrate layers under negative electrode and on the contact layer just Electrode.