Increasing the power conversion efficiency of silicon (Si) photovoltaics is a key enabler for continued reductions in the cost of solar electricity. Disclosed herein is a multi-junction photovoltaic cell that does not utilize a conventional interconnection layer and instead places a wide bandgap oxide conductor, for example, a metal oxide such as TiO.sub.2, between a top light absorption layer having a relatively large bandgap and a bottom light absorption layer having a relatively small bandgap. The advantageous omission of a conventional interconnection layer between the two subcells is enabled by low contact resistivity between the top and bottom light absorbing layers provided by the wide bandgap oxide conductor. The absence of the conventional interconnect between the subcells significantly reduces both optical losses and processing steps. The disclosed photovoltaic cell may thus enable low-cost, high-efficiency multi-junction devices through less complex manufacturing processes and lower material costs.

Ways of making and using tandem photovoltaic devices are provided, where such devices can include a first submodule, a second submodule, and an interface between the first submodule and the second submodule. The interface permits a portion of light to pass therethrough and optically couples the first submodule and the second submodule. Optically coupling the first submodule and the second submodule includes reducing reflection of the portion of light passing through the interface.

Systems and methods are provided for wirelessly transferring power to a multi junction photovoltaic cell of a space apparatus via a light emission system. The light emission system uses multiple lasers emitting different wavelengths and/or photon energies to produce electron-hole pairs in each layer of the multi junction photovoltaic cell to prompt power generation by the multi junction photovoltaic cell. The light emission system may be located on Earth or on another space apparatus. The multi junction photovoltaic cell can convert sunlight and the light emitted by the light emission system into electrical energy.

In one aspect, optoelectronic devices are described herein. In some implementations, an optoelectronic device comprises a photovoltaic cell. The photovoltaic cell comprises a space-charge region, a quasi-neutral region, and a low bandgap absorber region (LBAR) layer or an improved transport (IT) layer at least partially positioned in the quasi-neutral region of the cell.

A multijunction solar cell including an upper first solar subcell having an emitter and base layers forming a photoelectric junction; a second solar subcell disposed under and adjacent to the upper first solar subcell, and having an emitter and base layers forming a photoelectric junction; and a third solar subcell disposed under and adjacent to the second solar subcell and having an emitter and base layers forming a photoelectric junction; wherein at least one of the base and emitter layers of at least a particular solar subcell from among the upper first solar subcell, the second solar subcell, and the third solar subcell has a graded band gap throughout at least a portion of thickness of its active layer adjacent to the photoelectric junction and being in a range of 20 to 300 MeV less than a band gap in the active layer in both the emitter layer and the base layer spaced away from the photoelectric junction.

An optical blocking region formed with patterned metal reduces light reflection toward pixel sensors in a pixel sensor array. The optical blocking region may be formed of a metal nanoscale grid in order to reflect more light away from the pixel sensors. The optical blocking region may include a dielectric layer, supporting the patterned metal, with high absorption structures or shallow deep trench isolation structures in order to increase absorption and thus reduce light reflection toward the pixel sensors.

A photovoltaic device includes a substrate, a semiconductor stack and a transparent tunnel junction. The semiconductor stack includes an n-type layer selected from a first transparent conductive oxide layer, or a window layer, or both; and a p-type absorber layer disposed on the n-type layer, wherein the absorber layer consists essentially of CdSexTe(1-x), wherein x is from 1 to about 40 at. %. The transparent tunnel junction comprises a transparent interface layer of Cd.sub.yZn.sub.(1-y)Te doped to be p+type, and a transparent contact layer doped to be n+type, and the interface layer is disposed between the p-type absorber layer and the transparent contact layer. In bifacial embodiments, the tunnel junction forms a transparent back contact and electrode; and in multi-junction embodiments, the tunnel junction forms a diode-like connector between top and bottom cells. The transparent contact layer may comprise tin oxide or zinc oxide doped with aluminum, fluorine or indium. The photovoltaic device may also include an electron reflector layer and/or an optical reflector layer.

A photovoltaic device includes a substrate, a semiconductor stack and a transparent tunnel junction. The semiconductor stack includes an n-type layer selected from a first transparent conductive oxide layer, or a window layer, or both; and a p-type absorber layer disposed on the n-type layer, wherein the absorber layer consists essentially of CdSexTe(1-x), wherein x is from 1 to about 40 at. %. The transparent tunnel junction comprises a transparent interface layer of Cd.sub.yZn.sub.(1-y)Te doped to be p+type, and a transparent contact layer doped to be n+type, and the interface layer is disposed between the p-type absorber layer and the transparent contact layer. In bifacial embodiments, the tunnel junction forms a transparent back contact and electrode; and in multi-junction embodiments, the tunnel junction forms a diode-like connector between top and bottom cells. The transparent contact layer may comprise tin oxide or zinc oxide doped with aluminum, fluorine or indium. The photovoltaic device may also include an electron reflector layer and/or an optical reflector layer.

A method of fabricating multijunction solar cell including an upper solar subcell and having an emitter of p conductivity type with a first band gap, and a base of n conductivity type with a second band gap greater than the first band gap; a lower solar subcell disposed below the upper solar subcell having an emitter of p conductivity type with a third band gap, and a base of n conductivity type with a fourth band gap greater than the third band gap; and an intermediate grading interlayer disposed between the upper and lower solar subcells and having a graded lattice constant that matches the upper first subcell on a first side and the second solar subcell on the second side opposite the first side, and having a fifth band gap that is greater than the second band gap of the upper solar subcell.

A method of fabricating multijunction solar cell including an upper solar subcell and having an emitter of p conductivity type with a first band gap, and a base of n conductivity type with a second band gap greater than the first band gap; a lower solar subcell disposed below the upper solar subcell having an emitter of p conductivity type with a third band gap, and a base of n conductivity type with a fourth band gap greater than the third band gap; and an intermediate grading interlayer disposed between the upper and lower solar subcells and having a graded lattice constant that matches the upper first subcell on a first side and the second solar subcell on the second side opposite the first side, and having a fifth band gap that is greater than the second band gap of the upper solar subcell.