Flexible Crystalline Ultra-Thin Si Solar Cells

A method for making a crystalline ultra-thin silicon (Si) solar cell, comprising:

• receiving a pre-existing inflexible crystalline Si solar cell comprising a back contact layer;
• a back-surface field layer disposed on an upper surface of the back contact layer;
• a base layer disposed on an upper surface of the back-surface field layer;
• an emitter disposed on an upper surface of the base layer, a front side of the emitter having a textured surface;
• an antireflective coating (ARC) layer disposed on the textured front side of the emitter;
• and a plurality of first top metal contact grids on an upper surface of the ARC layer, the metal contact grids extending from below the front surface of the emitter to above the front surface of the ARC layer;
• preparing a carrier substrate by depositing a first adhesion layer on an upper surface of a flexible, conductive foil;
• depositing a first metal base layer on an upper surface of the adhesion layer;
• and depositing a first metal interlayer on an upper surface of the first metal base layer;
• preparing the pre-existing inflexible crystalline Si solar cell for mounting on the carrier substrate, the preparation including depositing a planarization metal layer on an upper surface of the ARC layer;
• depositing a second adhesion layer on an upper surface of the planarization metal layer;
• depositing a second metal base layer on an upper surface of the second adhesion layer;
• and depositing a second metal interlayer on an upper surface of the second metal base layer, the second adhesion layer, the second metal base layer, and the second metal interlayer being formed from the same material as the corresponding first adhesion layer, first metal base layer, and first metal interlayer in the carrier substrate;
• inverting the prepared pre-existing inflexible crystalline Si solar cell to that the second metal interlayer in the pre-existing inflexible crystalline Si solar cell faces the first metal interlayer in the carrier substrate;
• bonding the inverted pre-existing inflexible crystalline Si solar cell to the carrier substrate to form a bonded structure situated on the flexible conductive foil, wherein the first metal interlayer is bonded to the second metal interlayer to form a blended bonded metal layer comprising metals from the first and second metal interlayers mixed with metals from the first and second metal base layers, and wherein the first textured ARC and the first metal grid pillars are contained within the bonded structure;
• completely removing the back layer and the back surface field layer from the bonded structure;
• partially removing the base layer from the bonded structure so that the remaining base layer has a reduced thickness of between about 1 and about 30 μm;
• texturing a front surface of the remaining base layer;
• depositing a passivating tunneling layer on the textured front surface of the base layer;
• depositing carrier-selective contact layers on the passivating tunnel layer;
• depositing a transparent conducting oxide (TCO) layer on the carrier-selective layer;
• and
• forming a set of second top metal contact grids on a front surface of the TCO layer, the second top metal contact grids extending from below the front surface of the base layer to above the front surface of the TCO layer;
• wherein the total thickness of the ultra-thin Si regions in the completed solar cell is between about 1 and about 20 μm.