1. A solar cell comprising:
a silicon substrate;
a buffer layer disposed on a side of the silicon substrate;
a germanium junction disposed on a side of the buffer layer opposite the silicon substrate;
a first electrode electrically connected to the germanium junction;
a first junction disposed on the germanium junction opposite the silicon substrate and having a band gap energy of about 0.7 electron volt to about 1.5 electron volts;
a second junction disposed on the first junction opposite the silicon substrate and having a band gap energy of about 1.5 electron volts to about 3.0 electron volts; and
a second electrode disposed on the second junction,
wherein the buffer layer is disposed between the silicon substrate and the germanium junction, and has a lattice constant that increases in a direction from the silicon substrate to the germanium junction, and
wherein the buffer layer comprises GaAsxP1-x wherein 0\u2266x\u22661, Ga1-yInyP wherein 0\u2266y\u22661, AlAszP1-z wherein 0\u2266z\u22661, or a combination thereof and wherein x in GaAsxP1-x varies in proportion to a distance from the silicon substrate to the germanium junction.
2. The solar cell of claim 1, wherein the buffer layer has a lattice constant satisfying the following Equation 1:
CSi\u22120.1 \u212b\u2266Cb\u2266CGe+0.1 \u212b,\u2003\u2003Equation 1
wherein
CSi is a lattice constant of the silicon substrate,
Cb is a lattice constant of the buffer layer, and
CGe is a lattice constant of the germanium junction.
3. The solar cell of claim 2, wherein a portion of the buffer layer contacting the silicon substrate has a lattice constant satisfying the following Equation 2:
CSi\u22120.05 \u212b\u2266Cb1\u2266CSi+0.05 \u212b,\u2003\u2003Equation 2
wherein
CSi is a lattice constant of the silicon substrate, and
Cb1 is a lattice constant of the portion of the buffer layer contacting the silicon substrate.
4. The solar cell of claim 2, wherein a portion of the buffer layer contacting the germanium junction has a lattice constant satisfying the following Equation 3:
CGe\u22120.05 \u212b\u2266Cbn\u2266CGe+0.05 \u212b,\u2003\u2003Equation 3
wherein
CGe is a lattice constant of the germanium junction, and
Cbn is a lattice constant of the portion of the buffer layer contacting the germanium junction.
5. The solar cell of claim 1, wherein the buffer layer comprises a plurality of layers and the lattice constant of the buffer layer varies discontinuously.
6. The solar cell of claim 5, wherein each layer of the plurality of layers independently has a thickness of about 0.1 micrometers to about 5 micrometers.
7. The solar cell of claim 5, wherein the plurality of layers of the buffer layer comprises a first layer contacting the silicon substrate and having a first lattice constant and an nth layer contacting to the germanium junction and having an nth lattice constant, and the lattice constant of each layer of the plurality of layers increases in a direction from the first layer to the nth layer.
8. The solar cell of claim 1, wherein the silicon substrate has a thickness of about 50 micrometers to about 1000 micrometers.
9. The solar cell of claim 1, wherein the buffer layer has a thickness of about 1 micrometer to about 10 micrometers.
10. The solar cell of claim 1, wherein the germanium junction has a thickness of about 1 micrometer to about 3 micrometers.
11. The solar cell of claim 1, further comprising at least one junction disposed between the germanium junction and the second electrode.
12. The solar cell of claim 11, wherein the at least one junction between the germanium junction and the second electrode comprises junction having a band gap energy of about 0.7 electron volt to about 3.0 electron volts.
13. The solar cell of claim 12, wherein
the first junction comprises GaAs, and
the second junction comprises GaInP.
14. The solar cell of claim 11, wherein the at least one junction disposed between the germanium junction and the second electrode has a band gap energy that increases in a direction from the germanium junction to the second electrode.
15. A method of manufacturing a solar cell, the method comprising:
providing a silicon substrate;
disposing a buffer layer on a side of the silicon substrate;
disposing a germanium junction on a side of the buffer layer opposite the silicon substrate;
disposing a first electrode electrically connected to the germanium junction;
disposing a first junction having a band gap energy of about 0.7 electron volt to about 1.5 electron volts on the germanium junction opposite the silicon substrate;
disposing a second junction having a band gap energy of about 1.5 electron volts to about 3.0 electron volts on the first junction opposite the silicon substrate; and
disposing a second electrode on the second junction,
wherein the buffer layer is disposed between the silicon substrate and the germanium junction, and has a lattice constant that increases in a direction from the silicon substrate to the germanium junction, and
wherein the buffer layer comprises GaAsxP1-x wherein 0\u2266x\u22661, Ga1-yInyP wherein 0\u2266y\u22661, AlAszP1-z wherein 0\u2266z\u22661, or a combination thereof and wherein x in GaAsxP1-x varies in proportion to a distance from the silicon substrate to the germanium junction.
16. The method of claim 15, wherein the buffer layer has a lattice constant satisfying the following Equation 1:
CSi\u22120.1 \u212b\u2266Cb\u2266CGe+0.1 \u212b\u2003\u2003Equation 1
wherein
CSi is a lattice constant of the silicon substrate,
Cb is a lattice constant of the buffer layer, and
CGe is a lattice constant of the germanium junction.
17. The method of claim 15, wherein the disposing a germanium junction comprises molecular beam epitaxy, metal-organic chemical vapor deposition, chemical beam epitaxy, or a combination thereof.
18. The method of claim 15, further comprising forming at least one junction on a side of the germanium junction before disposing the first and second electrodes.
19. The method of claim 18, wherein the at least one junction on a side of the germanium junction has a band gap energy of about 0.7 electron volt to about 3.0 electron Volts.
20. The method of claim 19, wherein the band gap energy of the at least one junction on a side of the germanium junction increases in proportion to a distance from the germanium junction.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. A chiral copper complex catalyst composition, which is obtained by
contacting an optically active N-salicylideneaminoalcohol compound of formula (1):
8
with a mono-valent or di-valent copper compound in an inert solvent,
wherein R1 represents
an alkyl group which may be substituted with a group selected from an alkoxy group, an aralkyloxy group, an aryloxy group and cycloalkoxy group,
an aralkyl, aryl or cycloalkyl group all of which may be substituted with a group selected from an alkyl group, an alkoxy group, an aralkyloxy group, an aryloxy roup, and a cycloalkoxy group,
R2 represent
a hydrogen atom, an alkyl group, a cycloalkyl group, or
an aralkyl or phenyl group which may be substituted with a group selected from an alkyl group, an alkoxy group, an aralkyloxy group, an aryloxy group and a cycloalkoxy group,
X1 and X2 are the same or different and independently represent a hydrogen atom, a halogen atom, a nitro group, an alkyl group, an alkoxy group or a cyano group, and two adjacent X1 and X2 together with the benzene ring to which they are bonded may form a 1-hydroxy-2- or 2-hydroxy-1-naphthyl group, and
the carbon atom denoted by * is an asymmetric carbon atom having either an S or R configuration, and
the amount of the mono-valent or di-valent copper compound is less than 1 mole per 1 mole of the optically active N-salicylideneaminoalcohol compound of formula (1).
2. A process for producing an optically active cyclopropane-carboxylic acid ester of formula (2):
9
wherein R3, R4, R5 and R6 are as defined below, and
R7 represents
an alkyl group having 1 to 8 carbon atoms,
a cycloalkyl group which may be optionally substituted with a lower alkyl group,
a benzyl group or phenyl group which may be optionally substituted with a lower alkyl group, a lower alkoxy group or a phenoxy group,
which comprises the steps of:
(a) contacting an optically active N-salicylideneaminoalcohol compound of formula (1):
10
with a mono-valent or di-valent copper compound, in an inert solvent,
wherein R1 represents
an alkyl group which may be substituted with a group selected from an alkoxy group, an aralkyloxy group, an aryloxy group, and cycloalkoxy group,
an aralkyl, aryl or cycloalkyl group all of which may be substituted with a group selected from an alkyl group, an alkoxy group, an aralkyloxy group, an aryloxy roup, and a cycloalkoxy group,
R2 represent
a hydrogen atom, an alkyl group, a cycloalkyl group, or an aralkyl or phenyl group which may be substituted with a group selected from an alkyl group, an alkoxy group, an aralkyloxy group, an aryloxy group, and a cycloalkoxy group,
X1 and X2 are the same or different and independently represent a hydrogen atom, a halogen atom, a nitro group, an alkyl group, an alkoxy group or a cyano group, and two adjacent X1 and X2 together with the benzene ring to which they are bonded may form a 1-hydroxy-2- or 2-hydroxy-1-naphthyl group, and
the carbon atom denoted by * is an asymmetric carbon atom having either an S or R configuration, and
the amount of the mono-valent or di-valent copper compound is less than 1 mole per 1 mole of the optically active N-salicylideneaminoalcohol compound of formula (1), and
(b) reacting a prochiral olefin of formula (3):
11
wherein R3, R4, R5 and R6 independently represent
a hydrogen atom,
a halogen atom,
a (C1-C10)alkyl group which may be substituted with a halogen atom or a lower alkoxy group,
a (C4-C8)cycloalkyl group,
an aryl group which may be substituted with a halogen atom, a lower alkyl group or a lower alkoxy group,
R3 and R4, or R5 and R6 may be bonded at their terminals to form an alkylene group having 2-4 carbon atoms, and
one of R3, R4, R5 and R6 groups represents an alkenyl group which may be substituted with a halogen atom, an alkoxy group or an alkoxy carbonyl group, of which alkoxy may be substituted with a halogen atom or atoms,
provided that when R3 and R5 are the same, R4 and R6 are not the same,
with a diazoacetic acid ester of formula (4):
N2CHCO2R7(4)
wherein R7 is the same as defined above, in the presence of a chiral copper complex catalyst composition so produced in step (a).