Axially-integrated epitaxially-grown tandem wire arrays

1. A plurality of vertically aligned nano- or micro-wires, each nano- or micro-wire of the plurality of nano- or micro-wires comprising:

at least one first segment comprising a first semiconducting material, and

at least one second segment comprising a second semiconducting material different than the first semiconducting material,

wherein the at least first segment and the at least second segment are axially integrated

wherein each first segment of the at least one first segment is separated from each second segment of the at least one second segment by an ohmic contact, wherein the ohmic contact has a graded composition to obtain lattice matching and includes a tunnel junction,

wherein each nano- or micro-wire of the plurality of nano- or micro-wires has a dimension comprising a mean diameter of about 500 nm to about 10 micrometers and a mean length of about 1 micrometer to 1 mm and having an aspect ratio of greater than 1; wherein at least a portion of each nano- or micro-wire of the plurality of nano- or micro-wires contacts a liquid and wherein at least one end of each nano- or microwire of the plurality of nano- or micro-wires is coated with a hydrogen or oxygen evolution catalyst; and

each nano- or micro-wire of the plurality of nano- or micro-wires is partially embedded in an ion conducting material with the at least one end coated with the hydrogen or oxygen evolution catalyst is free of the ion conducting material.

2. The plurality of nano- or micro-wires of claim 1 , wherein the ohmic contact and that at least one second segment comprise a semiconducting material individually selected from the group consisting of TiO 2 , CaTiO 3 , SrTiO 3 , Sr 3 Ti 2 O 7 , Sr 4 Ti 3 O 10 , Rb 2 La 2 Ti 3 O 10 , Cs 2 La 2 Ti 3 O 10 , CsLa 2 Ti 2 NbO 10 , La 2 TiO 5 , La 2 Ti 3 O 9 , La 2 Ti 2 O 7 , La 2 Ti 2 O 7 :Ba, KaLaZr 0.3 Ti 0.7 O 4 , La 4 CaTi 5 O 17 , KTiNbO 5 , Na 2 Ti 6 O 13 , BaTi 4 O 9 , Gd 2 Ti 2 O 7 , Y 2 Ti 2 O 7 , ZrO 2 , K 4 Nb 6 O 17 , Rb 4 Nb 6 O 17 , Ca 2 Nb 2 O 7 , Sr 2 Nb 2 O 7 , Ba 5 Nb 4 O 15 , NaCa 2 Nb 3 O 10 , ZnNb 2 O 6 , Cs 2 Nb 4 O 11 , La 3 NbO 7 , Ta 2 O 5 , KsPrTa 5 O 15 , K 3 Ta 3 Si 2 O 13 , K 3 Ta 3 B 2 O 12 , LiTaO 3 , KTaO 3 , AgTaO 3 , KTaO 3 :Zr, NaTaO 3 :La, NaTaO 3 :Sr, Na 2 Ta 2 O 6 , CaTa 2 O 6 , SrTa 2 O 6 , NiTa 2 O 6 , Rb 4 Ta 6 O 17 , Ca 2 Ta 2 O 7 , Sr 2 Ta 2 O 7 , K 2 SrTa 2 O 7 , RbNdTa 2 O 7 , H 2 La 2/3 Ta 2 O 7 , K 2 Sr 1.5 Ta 3 O 10 , LiCa 2 Ta 3 O 10 , KBa 2 Ta 3 O 10 , Sr 5 Ta 4 O 15 , Ba 2 Ta 4 O 15 , H 1.8 Sr 0.81 Bi 0.19 Ta 2 O 7 , Mg—Ta Oxide, LaTaO 4 , LaTaO 7 , PbWO 4 , RbWNbO 6 , RbWTaO 6 , CeO 2 :Sr, BaCeO 3 , NaInO 2 , CaIn 2 O 4 , SrIn 2 O 4 , LaInO 3 , Y x In 2-x O 3 , NaSbO 3 , CaSb 2 O 6 , Ca 2 Sb 2 O 7 , Sr 2 Sb 2 O 7 , Sr 2 SnO 4 , ZnGa 2 O 4 , Zn 2 GeO 4 , LiInGeO 4 , Ga 2 O 3 b , Ga 2 O 3 :Zn c , Na 2 Ti 3 O 7 , K 2 Ti 2 O 5 , K 2 Ti 4 O 9 , Cs 2 Ti 2 O 5 , H + —Cs 2 Ti 2 O 5 , Cs 2 Ti 5 O 11 , Cs 2 Ti 6 O 13 , H + —CsTiNbO 5 , H + —CsTi 2 NbO 7 , SiO 2 -pillared K 2 Ti 4 O 9 , SiO 2 -pillared K 2 Ti 2.7 Mn 0.3 O 7 , Na 2 W 4 O 13 , H + —KLaNb 2 O 7 , H + —RbLaNb 2 O 7 , H + —CsLaNb 2 O 7 , H + —KCa 2 Nb 3 O 10 , SiO 2 -pillared KCa 2 Nb 3 O 10 , ex-Ca 2 Nb 3 O 10/ K + nanosheet 4) , Restacked ex-Ca 2 Nb 3 O 10 /Na + , H + —RbCa 2 Nb 3 O 10 , H + —CsCa 2 Nb 3 O 10 , H + —KSr 2 Nb 3 O 10 , H + —KCa 2 NaNb 4 O 13 , Bi 2 W 2 O 9 , Bi 2 Mo 2 O 9 , Bi 4 Ti 3 O 12 , BaBi 4 Ti 4 O 15 , Bi 3 TiNbO 9 , PbMoO 4 , (NaBi) 0.5 MoO 4 , (AgBi) 0.5 MoO 4 , (NaBi) 0.5 WO 4 , (AgBi) 0.5 WO 4 , Ga 1.14 In 0.86 O 3 , β-Ga 2 O 3 , Ti 1.5 Zr 1.5 (PO 4 ) 4 , WO 3 , Bi 2 WO 6 , Bi 2 MoO 6 , Bi 2 Mo 3 O 12 , Zn 3 V 2 O 8 , Na 0.5 Bi 1.5 VMoO 8 , In 2 O 3 (ZnO) 3 , SrTiO 3 :Cr/Sb, SrTiO 3 :Ni/Ta, SrTiO 3 :Cr/Ta, SrTiO 3 :Rh, CaTiO 3 :Rh, La 2 Ti 2 O 7 :Cr, La 2 Ti 2 O 7 :Fe, TiO 2 :Cr/Sb, TiO 2 :Ni/Nb, TiO 2 :Rh/Sb, PbMoO 4 :Cr, RbPb 2 Nb 3 O 10 , PbBi 2 Nb 2 O 9 , BiVO 4 , BiCu 2 VO 6 , BiZn 2 VO 6 , SnNb 2 O 6 , AgNbO 3 , Ag 3 VO 4 , AgLi 1/3 Ti 2/3 O 2 , AgLi 1/3 Sn 2/3 O 2 , LaTiO 2 N, Ca 0.25 La 0.75 TiO 2.25 N 0.75 , TaON, Ta 3 N 5 , CaNbO 2 N, CaTaO 2 N, SrTaO 2 N, BaTaO 2 N, LaTaO 2 N, Y 2 Ta 2 O 5 N 2 , TiN x O y F z , Sm 2 Ti 2 O 5 S 2 , La—In oxysulfide, GaAs, GaP, GaAs x P 1-x , Al x Ga 1-x , As, Al x Ga 1-x As y P 1-y , In x Ga 1-x As, In x Ga 1-x P, In x Ga 1-x As y P 1-y , Al x In 1-x As y P 1-y , Al x Ga 1-x As y N z P 1-y-z , In x Ga 1-x As y N z P 1-y-z , Zn 3 P 2 , Zn 3 S 2 , and ZnP x S 1-x (0≤x≤1, 0≤y≤1, 0≤z≤1, 0≤y+z≤1).

3. The plurality of nano- or micro-wires of claim 1 , wherein the first semiconducting material is silicon.

4. The plurality of nano- or micro-wires of claim 1 , wherein the at least one first segment is surface coated by a passivation layer.

5. The plurality of nano- or micro-wires of claim 1 , wherein the ion conducting material forms a membrane comprising the plurality of nano- or micro-wires embedded in the ion conducting material extending from and/or through a first surface to and/or through a second surface of the membrane.

6. The plurality of nano- or micro-wires of claim 1 , wherein the first semiconducting material includes a radial p-n junction or a radial p-i-n junction.

7. The plurality of nano- or micro-wires claim 6 , wherein the second different semiconducting material includes a radial p-n junction or a radial p-i-n junction.

8. The plurality of nano- or micro-wires claim 1 , wherein the plurality of nano- or micro-wires are included in a water splitting device.

9. The plurality of nano- or micro-wires of claim 1 , wherein one end of each nano- or micro-wire of the plurality of nano- or micro-wires is in contact with the liquid.

10. The plurality of nano- or micro-wires of claim 1 , wherein the plurality of nano- or micro-wires are epitaxially grown.

11. The plurality of nano- or micro-wires of claim 1 , wherein the ohmic contact is in physical contact with both the at least one first segment and the at least one second segment of each nano- or micro-wire of the plurality of nano- or micro-wires.