High efficiency Inverted Metamorphic (IMM) solar cells

Abstract

High efficiency Inverted Metamorphic (IMM) multi-junction solar cells have been under development at Spectrolab for use in space and near space applications This paper reviews the present state-of-the-art of this technology at Spectrolab with an emphasis on performance characterization data at in-flight operating conditions. Large area IMM3J and IMM4J solar cells with 1X AM0 efficiency greater than 32% at 28 °C have been fabricated and characterized. Degradation factors after exposure to 1 MeV electron irradiation for both IMM3J and IMM4J technologies is presented. A coupon utilizing large area, IMM solar cells has been assembled and subjected to thermal cycling. Pre-and post thermal cycling data have been collected. Preliminary temperature cycling data indicate that a small coupon populated with strings of these cells suffered no degradation.

Radiation degradation characteristics of component subcells in inverted metamorphic triple-junction solar cells irradiated with electrons and protons

“…At present, the inverted metamorphic (IMM) multi‐junction (MJ) solar cells formed of In 0.5 Ga 0.5 P/GaAs/In x Ga 1‐x As material system have received considerable attention and are being developed as next‐generation space solar cells owing to their higher conversion efficiency compared with the currently used conventional In 0.5 Ga 0.5 P /GaAs/Ge triple‐junction space solar cells . In addition, the IMM‐MJ cells are essentially lightweight thin film cells, because the semiconductor layers constituting the solar cell structure are inversely grown on the substrates, which are subsequently removed during the device fabrication process.…”

“…The same structures of the top InGaP and middle GaAs subcells in the current space 3J can be fundamentally applied to the space IMM3J cells. Practically, several types of IMM‐MJ space solar cells have been developed on the basis of the knowledge from the present space 3J cells . However, additional modification and improvement of the structure becomes possible once further knowledge on radiation degradation characteristics of such lattice‐mismatched InGaAs cells is gained.…”

The Physics of High-Efficiency Thin-Film III-V Solar Cells

“…By stacking multiple p-n junctions of different III-V semiconductor materials into one twoterminal device, multi-junction solar cells have achieved record-high efficiency at converting solar power into electrical power. Under air mass zero (AM0) spectral conditions found in space, InGaP/GaAs/InGaAs inverted metamorphic (IMM) cells have been demonstrated with efficiencies in excess of 32% [3][4]. Even higher efficiencies exceeding 35% have been achieved under an air mass spectrum (AM1.5) typically used to characterize terrestrial performance [5].…”

Fabrication and Irradiation Effect of Inverted Metamorphic Triple Junction GaInP/GaAs/InGaAs Solar Cells

“…Moreover, the inverted growth of the subcells minimizes the effect of dislocation propagation from the buffer layer [11][12][13]. At present, the inverted metamorphic triple-junction (IMM3J) GaInP/GaAs/InGaAs solar cell has a high conversion efficiency of 37.9% (AM1.5,1-sun) [14] and 32.1% (AM0, 1-sun) [15]. Furthermore, the weight and cost of IMM3J solar cells can be greatly reduced by removing GaAs substrates [16].…”

“…Therefore, to meet the requirements of space applications, we need to imitate the real space environment as much as possible to carry out electron and proton irradiation experiments with different energies and fluences on solar cells. The effects of 1 MeV electron irradiation on IMM3J solar cells have been studied by spectral response, photoluminescence and electrical properties [15,19,20]. The radiation resistance of IMM3J solar cells can also be investigated by analyzing the degradation of each subcell (InGaP, GaAs, and InGaAs) under electron and proton irradiation [17].…”