A method of is provided as a process of substrate lift-off. The present invention is mainly used for a group III-V solar cell, which has the highest power generation efficiency. An original sacrificial layer is changed into an AlAs oxide layer, which is transformed into an AlO.sub.x sacrificial layer after wet oxidation. The sacrificial layer is then soaked in an oxide-relief solution for etching. Thus, the lift-off process of a GaAs substrate can be harmlessly processed to the complex group III-V solar cell. The GaAs substrate can be recycled to be effectively further reused in photovoltaic devices with reduced cost.

A tandem solar cell includes a substrate a plurality of sub-cells stacked on the substrate and configured to sequentially perform photoelectric conversion with different wavelength band, and a metal disk array disposed on at least one of interfaces between adjacent sub-cells. A center wavelength of wavelength bands corresponding to the sub-cells gradually decreases as progressing downward with respect to an uppermost layer. The metal disk array reflects a light transmitting a sub-cell disposed over the metal disk array without being absorbed therein. The metal disk array is inserted by means of wafer bonding.

A growth structure having a lattice transition under a release layer is used as a seed crystal for growth of optoelectronic devices. The optoelectronic device can be a single- or multi-junction photovoltaic device. The release layer can be selectively removed in an epitaxial lift-off (ELO) process to separate the optoelectronic device from the growth structure and leave the region with the lattice transition intact to reuse the growth structure to grow additional devices. A manufacturing method is described that includes providing a growth structure having a substrate and a lattice transition from a first lattice constant to a second lattice constant, depositing a release layer on the growth structure, depositing on the release layer an epitaxial layer having a lattice constant that matches the second lattice and including an optoelectronic device, and removing the release layer to separate the epitaxial layer and the optoelectronic device from the growth structure.

There is provided a multi-junction solar cell comprising: a target subcell, a diffraction grating, a transparent spacer layer, a distributed Bragg reflector, and a lower subcell.

A solar cell comprising a bulk germanium silicon growth substrate; a diffused photoactive junction in the germanium silicon substrate; and a sequence of subcells grown over the substrate, with the first grown subcell either being lattice matched or lattice mis-matched to the growth substrate.

A solar cell with lightweight support structure and a method of manufacturing the same are provided. The solar cell includes: a composite substrate; a photoelectric conversion structure disposed on the composite substrate, and including a light receiving side and a back side which is opposite the light receiving side; a front electrode formed on the light receiving side; and a back electrode formed on the back side, where the composite substrate includes an optical reflective layer which is connected with the back side of the photoelectric conversion structure; and where the photoelectric conversion structure includes at least one Group III-V compound semiconductor layer.

A multijunction solar cell including a metamorphic layer, and particularly the design and specification of the composition, lattice constant, and band gaps of various layers above the metamorphic layer in order to achieve reduction in bowing of the semiconductor wafer caused by the lattice mismatch of layers associated with the metamorphic layer.

A multijunction solar cell and its method of fabrication, having an upper first solar subcell composed of a semiconductor material including aluminum and having a first band gap; a second solar subcell adjacent to said first solar subcell and composed of a semiconductor material having a second band gap smaller than the first band gap and being lattice matched with the upper first solar subcell; a third solar subcell adjacent to said second solar subcell and composed of a semiconductor material having a third band gap smaller than the second band gap and being lattice matched with the second solar subcell; a first and second DBR structure adjacent to the third solar subcell; and a fourth solar subcell adjacent to the DBR structures and lattice matched with said third solar subcell and composed of a semiconductor material having a fourth band gap smaller than the third band gap; wherein the fourth subcell has a direct bandgap of greater than 0.75 eV.

A multijunction solar cell and its method of fabrication, having an upper first solar subcell composed of a semiconductor material including aluminum and having a first band gap; a second solar subcell adjacent to said first solar subcell and composed of a semiconductor material having a second band gap smaller than the first band gap and being lattice matched with the upper first solar subcell; a third solar subcell adjacent to said second solar subcell and composed of a semiconductor material having a third band gap smaller than the second band gap and being lattice matched with the second solar subcell; a first and second DBR structure adjacent to the third solar subcell; and a fourth solar subcell adjacent to the DBR structures and lattice matched with said third solar subcell and composed of a semiconductor material having a fourth band gap smaller than the third band gap; wherein the fourth subcell has a direct bandgap of greater than 0.75 eV.

A stacked multi-junction solar cell with a first subcell having a top and a bottom, and with a second subcell. The first subcell is implemented as the topmost subcell so that incident light first strikes the top of the first subcell and after that strikes the second subcell through the bottom. A first tunnel diode is arranged between the bottom of the first subcell and the second subcell. A window layer is arranged on the top of the first subcell, and the band gap of the window layer is larger than the band gap of the first subcell. A cover layer is arranged below metal fingers and above the window layer, and an additional layer is arranged below the cover layer and above the window layer. A thickness of the additional layer is less than the thickness of the window layer.