Wide-bandgap, lattice-mismatched window layer for a solar conversion device

A photovoltaic cell comprising:

• at least one subcell, at least one of said at least one subcells having an emitter layer and a base layer, said base layer composed of a first material having a first material lattice constant;
• wherein said emitter layer is a heterojunction emitter layer composed of a second material, said second material having a second material lattice constant that is not equal to said first material lattice constant and wherein said first material lattice constant and said second material lattice constant differ in material lattice constant values by at least greater than approximately 1.0%, wherein said base layer is fully relaxed with respect to said emitter layer by virtue of dislocations in the crystal structure of said base layer.

A photovoltaic cell comprising:

• at least one subcell, at least one of said at least one subcells having an emitter layer and a base layer and a BSF layer, said base layer composing a second material having a second lattice constant;
• wherein said BSF layer is composed of a first material, said first material having a first material lattice constant that is not equal to said second material lattice constant and wherein said BSF layer is lattice mismatched by a material lattice constant value of at least greater than approximately 1.0% to said base layer, wherein said BSF layer is fully relaxed with respect to said base layer by virtue of dislocations in the crystal structure of said BSF layer.

A photovoltiac cell comprising:

• at least one subcell, at least one of said at least one subcells having an emitter layer and a base layer;
• and a lattice mismatched window layer positioned directly adjacent to said emitter layer, wherein said lattice mismatched window layer is composed of a first material, said first material having a first material lattice constant that is not equal to a second material lattice constant of a second material composing said emitter layer and is not equal to a third material lattice constant of a third material composing said base layer, wherein said first material lattice constant and said second material lattice constant differ in material lattice constant values by at least approximately 1.0% and wherein said first material lattice constant and said third material lattice constant differ in material lattice constant values by at least greater than approximately 1.0%, wherein said lattice mismatched window layer is fully relaxed with respect to said emitter layer by virtue of dislocations in the crystal structure of said lattice mismatched window layer.

A method for increasing current generation in a photovoltaic cell or other optoelectronic device, the method comprising the steps of:

• providing at least one subcell layer, wherein at least one of said at least one subcell layers has an emitter layer;
• and growing a lattice-mismatched window layer positioned directly adjacent to said emitter layer, wherein the lattice-mismatched window layer is composed of a first material, said first material having a first material lattice constant that is not equal to a second material lattice constant of a second material composing said emitter layer and wherein said first material lattice constant and said second material lattice constant differ in material lattice constant values by at least greater than approximately 1.0%, wherein said lattice mismatched window layer is fully relaxed with respect to said emitter layer by virtue of dislocations in the crystal structure of said lattice mismatched window layer.