Thin Multijunction Solar Cells

As future demands are made for higher efficiency (30+ %), improved Watt/weight (1000 W/kg), it is clear that new approach that combine best attribute of crystalline and thin film solar cells to achieve 1000 W/kg is needed. ELI propose to develop (1) Inverted structure of InGaP (1.8 ev)/GaAs (1.4 ev)/InGaAs (1.0 ev) triple junction solar cells (shown in Fig. 1a, similar to NREL structure) using combined in house Molecular Beam Epitaxy (MBE) and MOCVD approach for combining the best attributes of MBE and MOCVD to achieve 35+% efficiency with thinner structure for scale up production with reduced cost. MOCVD will be used to grow top two lattice matched sub cells(InGaP/GaAs) on GaAs substrate, and MBE will be used to grow strained buffer and bottom third InGaAs subcell (2) Novel scalable processes for removing GaAs substrate from inverted structure, and utilizing noval method(patent pending) to produce crack free solar arrays that is bonded to lightweight flexible substrate (1 mil thick Ti foil, or flexible kapton or polymer) for 1000 W/kg specific power and stowability.