A multijunction solar cell including an upper first solar subcell having a first band gap and positioned for receiving an incoming light beam; a second solar subcell disposed below and adjacent to and lattice matched with said upper first solar subcell, and having a second band gap smaller than said first band gap; wherein at least one of the solar subcells has a graded band gap throughout the thickness of at least a portion of the active layer.

A multijunction solar cell comprising a first solar subcell having a first band gap; a second solar subcell disposed adjacent to said first solar subcell and including an emitter layer, and a base layer having a second band gap less than the first band gap, and being lattice mismatched with the upper first solar subcell, and an intermediate layer directly adjacent to and disposed between first and the second solar subcells and compositionally graded to lattice match the first solar subcell on one side and the second solar subcell on the other side, and arranged so that light can enter and pass through the first solar subcell and at least a portion of which can be reflected back into the first solar subcell by the intermediate layer, and is composed of a plurality of layers of materials with discontinuities in their respective indices of refraction.

A multijunction solar cell comprising a first solar subcell having a first band gap; a second solar subcell disposed adjacent to said first solar subcell and including an emitter layer, and a base layer having a second band gap less than the first band gap, and being lattice mismatched with the upper first solar subcell, and an intermediate layer directly adjacent to and disposed between first and the second solar subcells and compositionally graded to lattice match the first solar subcell on one side and the second solar subcell on the other side, and arranged so that light can enter and pass through the first solar subcell and at least a portion of which can be reflected back into the first solar subcell by the intermediate layer, and is composed of a plurality of layers of materials with discontinuities in their respective indices of refraction.

A multijunction solar cell includes an upper solar subcell, a bottom solar subcell adjacent to the upper solar subcell, a layer of light scattering elements below and directly adjacent to the bottom solar subcell, and a metallic layer disposed below and adjacent to the layer of light scattering elements.

A tandem photovoltaic device includes: an upper cell unit, a lower cell unit and a tunnel junction positioned between the upper cell unit and the lower cell unit; the tunnel junction includes an upper transport layer, a lower transport layer, and an intermediate layer positioned between the upper transport layer and the lower transport layer, the intermediate layer is an ordered defect layer, or, the intermediate layer is a continuous thin layer, or, the intermediate layer includes a first layer in contact with the lower transport layer and a second layer in contact with the upper transport layer; a doping concentration of the first layer is 10-10,000 times of a doping concentration of the lower transport layer, and the doping concentration of the first layer is less than 10.sup.21cm.sup.−3; a doping concentration of the second layer is 10-10,000 times of a doping concentration of the upper transport layer.

The photoelectric conversion layer of an embodiment is based on Cu.sub.2O, contains at least one p-type dopant selected from the group consisting of Ge, Ta, and In, and has a band gap of equal to or more than 2.10 eV and equal to or less than 2.30 eV.

The photoelectric conversion layer of an embodiment is based on Cu.sub.2O, contains at least one p-type dopant selected from the group consisting of Ge, Ta, and In, and has a band gap of equal to or more than 2.10 eV and equal to or less than 2.30 eV.

A tandem photovoltaic device and production method. The tandem photovoltaic device includes: an upper battery cell and a lower battery cell, and a tunnel junction located between the upper battery cell and the battery cell; the lower battery is a crystalline silicon cell; the tunnel junction includes: an upper crystalline silicon layer, a lower crystalline silicon layer and an intermediate layer located between the upper crystalline silicon layer and the lower crystalline silicon layer; the upper crystalline silicon layer, the lower crystalline silicon layer and the intermediate layer are in direct contact, and the doping types of the upper crystalline silicon layer and the lower crystalline silicon layer are opposite; the doping concentration of the upper crystalline silicon layer at the interface with the intermediate layer and the doping concentration of the lower crystalline silicon layer at the interface with the intermediate layer are greater than or equal to 10.sup.18 cm.sup.−3.

A tandem photovoltaic device and production method. The tandem photovoltaic device includes: an upper battery cell and a lower battery cell, and a tunnel junction located between the upper battery cell and the battery cell; the lower battery is a crystalline silicon cell; the tunnel junction includes: an upper crystalline silicon layer, a lower crystalline silicon layer and an intermediate layer located between the upper crystalline silicon layer and the lower crystalline silicon layer; the upper crystalline silicon layer, the lower crystalline silicon layer and the intermediate layer are in direct contact, and the doping types of the upper crystalline silicon layer and the lower crystalline silicon layer are opposite; the doping concentration of the upper crystalline silicon layer at the interface with the intermediate layer and the doping concentration of the lower crystalline silicon layer at the interface with the intermediate layer are greater than or equal to 10.sup.18 cm.sup.−3.

An inverted metamorphic multijunction solar cell including an upper first solar subcell, a second solar subcell and a third solar subcell. The upper first solar subcell has a first band gap and positioned for receiving an incoming light beam. The second solar subcell is disposed below and adjacent to, and is lattice matched with, the upper first solar subcell, and has a second band gap smaller than the first band gap. The third solar subcell is disposed below the second solar subcell, and is composed of a GaAs base and emitter layer so as to optimize the efficiency of the solar cell after exposure to radiation. In some implementations, at least one of the solar subcells has a graded band gap throughout its thickness.