Summary of the invention
The object of this invention is to provide a kind of crystalline silicon containing lower conversion luminescence quantum dot utilizing said method to prepare, solve the light utilization efficiency of crystalline silicon near ultraviolet region in prior art low, the problem that solar cell conversion efficiency is low.
Another object of the present invention is to provide a kind of crystalline silicon preparation method containing lower conversion luminescence quantum dot.
The technical solution adopted in the present invention is, a kind of crystalline silicon containing lower conversion luminescence quantum dot, the concentration of the rare earth element in described crystalline silicon is 10
10~ 10
16atoms/cm
3.
Another technical scheme of the present invention is, a kind of crystalline silicon preparation method containing lower conversion luminescence quantum dot, implements according to following steps:
Step 1. mixes 8ppbw ~ 120ppmw rare earth element in solar-grade polysilicon raw material, utilizes conventional CZ legal system to obtain monocrystalline silicon, or utilizes ingot casting method to obtain polysilicon; The concentration of described monocrystalline silicon or polysilicon rare earth elements is 10
10~ 10
16atoms/cm
3;
The monocrystalline silicon that step 1 obtains by step 2. or polysilicon, carry out annealing in process at 700 DEG C ~ 1000 DEG C, obtains the monocrystalline silicon containing lower conversion luminescence quantum dot or polysilicon.
The invention has the beneficial effects as follows:
1) the method technique is simple, and cost is low, and lower conversion luminescence quantum dot can be utilized to significantly improve crystal-silicon solar cell conversion efficiency.
2) annealing steps in the present invention can make oxygen element in crystal reunite around rare earth element, the quantum-dot structure with fluorescent effect is formed in crystalline silicon, after this structure absorbs a high-energy photon, electron transition is to upper state, 2 lower energy photons are discharged afterwards when falling ground state after rise, 2 lower energy photons are absorbed by silicon substrate and form photo-generated carrier, thus improve high-energy photon utilization ratio, improve solar cell to the utilance of ultraviolet band region light, improve solar cell conversion efficiency.
3) silicon crystal adopting the inventive method to prepare is applied to solar cell, and because the electrology characteristic of rare earth ion is not so electrically aobvious in silicon single crystal, namely rare earth ion can not have an impact to the electric property of silicon materials; After annealed process simultaneously, form lower conversion luminescence quantum dot, effectively can improve the utilance of silicon materials to ultraviolet band light, utilize the obtained solar cell of this crystal to significantly improve conversion efficiency.
Embodiment
Monocrystalline silicon preparation method containing lower conversion luminescence quantum dot of the present invention, implements according to following steps:
Step 1. mixes 8ppbw ~ 120ppmw rare earth element in solar-grade polysilicon raw material, utilizes conventional CZ legal system to obtain monocrystalline silicon; The concentration of described monocrystalline silicon rare earth elements is 10
10~ 10
16atoms/cm
3, (atomic quantity namely in every cubic centimeter volume);
The preferred lanthanum of rare earth element (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), europium (Eu), terbium (Tb), dysprosium (Dy), one of ytterbium (Yb) or lutetium (Lu), or one of them oxide of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), europium (Eu), terbium (Tb), dysprosium (Dy), ytterbium (Yb) or lutetium (Lu);
The monocrystalline silicon that step 1 obtains by step 2., carries out annealing in process at 700 DEG C ~ 1000 DEG C, obtains the monocrystalline silicon containing lower conversion luminescence quantum dot.
Embodiment 1
Choose monocrystalline silicon A and monocrystalline silicon B, monocrystalline silicon A is that conventional CZ method obtains p type single crystal silicon, monocrystalline silicon B utilizes CZ method to obtain for mixing 50ppbw ytterbium (Yb) in solar-grade polysilicon raw material, monocrystalline silicon A, monocrystalline silicon B choose one section respectively, obtain monocrystalline silicon A ' section and monocrystalline silicon B ' section, wherein monocrystalline silicon A section and monocrystalline silicon B section do not carry out annealing in process, and monocrystalline silicon A ' section and monocrystalline silicon B ' section were 800 DEG C of annealing in process 2 hours; Four sections of crystal are carried out obtained solar cell of cutting into slices, and utilize characteristic of solar cell tester to carry out conversion efficiency detection, obtain following data, in table 1:
Table 1, embodiment 1 four sections of crystal carry out obtained solar cell conversion efficiency detection contrast of cutting into slices
Crystal is numbered |
Doped chemical kind |
Heat-treat condition |
Conversion efficiency |
Crystal A |
B |
Nothing |
18.11% |
Crystal B |
B+ ytterbium (Yb) |
Nothing |
18.17% |
Crystal A ' |
B |
800 DEG C of heat treatment 2 hours |
18.09% |
Crystal B ' |
B+ ytterbium (Yb) |
800 DEG C of heat treatment 2 hours |
18.44% |
Embodiment 2
Choose monocrystalline silicon C and monocrystalline silicon D, through crystalline silicon C be conventional CZ method obtain p type single crystal silicon, monocrystalline silicon D utilizes CZ method to obtain for mixing 100ppbw praseodymium (Pr) in solar-grade polysilicon raw material, monocrystalline silicon C and monocrystalline silicon D choose one section respectively, obtain monocrystalline silicon C ' section and monocrystalline silicon D ' section, wherein monocrystalline silicon C section and monocrystalline silicon D section do not carry out annealing in process, and monocrystalline silicon C ' section and monocrystalline silicon D ' section were 800 DEG C of annealing in process 2 hours; Four sections of crystal are carried out obtained solar cell of cutting into slices, and utilize characteristic of solar cell tester to carry out conversion efficiency detection, obtain following data, in table 2:
Table 2, embodiment 2 four sections of crystal carry out obtained solar cell conversion efficiency detection contrast of cutting into slices
Crystal is numbered |
Doped chemical kind |
Heat-treat condition |
Conversion efficiency |
Crystal C |
B |
Nothing |
18.01% |
Crystal D |
B+ praseodymium (Pr) |
Nothing |
18.05% |
Crystal C ' |
B |
800 DEG C of heat treatment 2 hours |
18.03% |
Crystal D ' |
B+ praseodymium (Pr) |
800 DEG C of heat treatment 2 hours |
18.28% |
Polysilicon preparation method containing lower conversion luminescence quantum dot of the present invention, implements according to following steps:
Step 1, in solar-grade polysilicon raw material, mix a kind of rare earth element of 8ppbw ~ 120ppmw, utilize ingot casting method, the concentration of obtained rare earth element is 10
10~ 10
16atoms/cm
3polysilicon, (atomic quantity namely in every cubic centimeter volume);
The preferred lanthanum of rare earth element (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), europium (Eu), terbium (Tb), dysprosium (Dy), one of ytterbium (Yb) or lutetium (Lu), or one of them oxide of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), europium (Eu), terbium (Tb), dysprosium (Dy), ytterbium (Yb) or lutetium (Lu);
Step 2, the polysilicon containing rare earth element step 1 obtained carry out annealing in process, and annealing temperature is 700 DEG C ~ 1000 DEG C, obtains the polysilicon containing lower conversion luminescence quantum dot.
Embodiment 3
Choose polysilicon E and polysilicon F, polysilicon E is that conventional foundry ingot method obtains P type polysilicon, polysilicon F utilizes ingot casting method to obtain for mixing 50ppbw ytterbium (Yb) in solar-grade polysilicon raw material, polysilicon E and polysilicon F choose one section respectively, obtain polysilicon E ' section and polysilicon F ' section, wherein polysilicon E section and polysilicon F section do not carry out annealing in process, and polysilicon E ' section and polysilicon F ' section were 800 DEG C of annealing in process 2 hours; Four sections of crystal are carried out obtained solar cell of cutting into slices, and utilize characteristic of solar cell tester to carry out conversion efficiency detection, obtain following data, in table 3:
Table 3, embodiment 3 four sections of crystal carry out obtained solar cell conversion efficiency detection contrast of cutting into slices
Crystal is numbered |
Doped chemical kind |
Heat-treat condition |
Conversion efficiency |
Crystal E |
B |
Nothing |
17.13% |
Crystal F |
B+ ytterbium (Yb) |
Nothing |
17.11% |
Crystal E ' |
B |
800 DEG C of heat treatment 2 hours |
17.15% |
Crystal F ' |
B+ ytterbium (Yb) |
800 DEG C of heat treatment 2 hours |
17.48% |
Embodiment 4
Choose polysilicon G and polysilicon H, polysilicon G is that conventional CZ method obtains p type single crystal silicon, polysilicon H utilizes CZ legal system to obtain crystalline silicon for mixing 100ppbw dysprosium (Dy) in solar-grade polysilicon raw material, polysilicon G and polysilicon H choose one section respectively, obtain polysilicon G ' section and polysilicon H ' section, wherein polysilicon G and polysilicon H does not carry out annealing in process, and polysilicon G ' section and polysilicon H ' section were 800 DEG C of annealing in process 2 hours; Four sections of crystal are carried out obtained solar cell of cutting into slices, and utilize characteristic of solar cell tester to carry out conversion efficiency detection, obtain following data, in table 4:
Table 4, embodiment 4 four sections of crystal carry out obtained solar cell conversion efficiency detection contrast of cutting into slices
Crystal is numbered |
Doped chemical kind |
Heat-treat condition |
Conversion efficiency |
Crystal G |
B |
Nothing |
17.02% |
Crystal H |
B+ dysprosium (Dy) |
Nothing |
17.06% |
Crystal G ' |
B |
800 DEG C of heat treatment 2 hours |
17.13% |
Crystal H ' |
B+ dysprosium (Dy) |
800 DEG C of heat treatment 2 hours |
17.21% |
Above-mentioned preparation method adopts the foundation of rare earth element to be that the architectural feature of rare earth element is outer and secondary skin is full of (6S all
25S
25P
6), and 5d shell is also empty or only have an electronics, the electron number be on the 4f track of internal layer is from 0 ~ 14, and the two-layer electronic structure of rare earth element outermost is similar, is all (n-1) S
2, (n-1) P
6, (n-1) d
0-1or (nS)
2.Rare earth element has the 4f shell of underfill and 4f electronics by 5S
25P
6the characteristic of electronic shield, makes rare earth element have extremely complicated class line spectrum.Meanwhile, because the characteristic of its electronic shield makes it not have electrical activity in crystalline silicon.
In the silicon crystal of doped with rare-earth elements, during high annealing, oxygen can be gathered in around rare earth element, oxygen CONCENTRATION DISTRIBUTION in the nearly body of silicon can become with rare earth element concentration, in the place that rare earth element concentration is large, the concentration of oxygen is also large, this is the polymer that can form with rare earth element the RE-O-Si being core, forms the quantum-dot structure with fluorescent effect in silicon crystal.
Lower transfer process is, by quantum-cutting, the high-energy photon being in ultraviolet band is converted to two or more lower energy photons, thus improves the capacity usage ratio of the single photon of ultraviolet region.The quantum-cutting system of embedded single rare earth in silicon crystal, raising photo-generated carrier number is a brand-new research direction.Such as will containing Pr
3+lower Pr is penetrated in silicon single crystal vacuum ultraviolet (VUV) (VUV) illumination of quantum dot
3+from ground state after absorption vacuum ultraviolet (VUV) (VUV) photon
3h
4transit to 4f5d configuration, 4f5d configuration lowest energy level is
1s
0energy level, then
1s
0fallen after rise to ground state by two steps, and discharge 2 photons, namely
1s
0→
1i
6,
3p
j(400nm) second step
3p
0→
3f
j,
3h
j(480 ~ 700nm), Pr
3+two photons of quantum dot release are absorbed by silicon crystal, excite acquisition two photo-generated carriers, thus reach the object improving photo-generated carrier number.