Improved radiation resistance of epitaxial lift-off inverted metamorphic solar cells

Abstract

The inverted metamorphic (IMM) solar cell has a high specific power compared to traditional germanium-based multi-junction solar cells, which may prove beneficial for space applications where costs are weight-driven. In addition, the mechanical flexibility of the IMM cell may be beneficial for new technologies, such as high-power, flexible, deployable arrays currently under development. However, IMM solar cells have not yet demonstrated radiation resistance equal to that of traditional Ge-based multi-junction cells, largely due to degradation in the InGaAs bottom subcell. A structure and process have been developed to incorporate a back surface reflector on the epitaxial lift-off (ELO) IMM solar cell, permitting the InGaAs subcell to be thinned whilst maintaining high optical absorption. The thinner subcell can better tolerate degraded base diffusion lengths following irradiation. In this manner, a significant improvement in the end of life efficiency of ELO IMM solar cells is demonstrated following irradiation with 1 MeV electrons at a fluence of 1x10 15 cm -2 .

Effect of 6 MeV electron irradiation on nano-Cu2ZnSnS4

“…All the spacecrafts and satellites use photovoltaic solar cell power in space as an energy source [1]. For many decades in conventional spacecrafts Si [2][3][4][5], multi junction solar cell [6][7][8][9] and GaAs/Ga are used [10][11][12][13] which provide high efficiency and are also quite robust to space environment. Researchers are trying to replace it with an alternate.…”

“…The energetic particles in space environments such as proton, electron, gamma etc. cause lattice damage in an active area of solar cell which degrades the performance of the solar cell used as a power sources in space satellite [10][11][12][13][14][15][16].This puts a limit on the use of solar cell for longer duration. Therefore, the stability of material which is used for making the solar cell for space application is very important.…”

Radiation Tolerant Nanowire Array Solar Cells

“…2 The second approach to mitigate radiation damage is to increase the intrinsic radiation tolerance of the solar cells through choice of semiconductor materials and/or device architectures with enhanced radiation robustness, which experience less degradation for a given radiation exposure. [3][4][5][6][7] State-of-the-art space solar panels composed of III-V multijunction solar cells 8,9 are attractive because of high power conversion efficiencies (>30 % under extraterrestrial solar spectrum (AM0)), enabling a reduction in the panel area for a given mission. The development of thinnedsubstrate 10 and epitaxial lift-off (ELO) 11 technologies have allowed extremely thin III-V solar cells to be produced, such that the mass of the panels using these cells would be dominated largely by 4 the requisite radiation-shielding.…”

“…First, a layer of shielding (typically a cerium-doped cover glass) is used to reduce the amount of radiation reaching the solar cells but this adds undesired weight . The second approach to mitigate radiation damage is to increase the intrinsic radiation tolerance of the solar cells through choice of semiconductor materials and/or device architectures with enhanced radiation robustness, which experience less degradation for a given radiation exposure. − …”

10 MeV proton irradiation effects on GaInP/GaAs/Ge concentrator solar cells and their component subcells

“…In the past decade, the lattice-matched GaInP/GaAs/Ge triple-junction solar cell (3JSC) has been chosen for space power generation in spacecrafts and satellites mainly as a result of its high efficiency (~30% at AM0), relatively high power-to-mass ratio and good radiation hardness [1][2][3]. Other existing multijunction solar cell architectures capable of achieving higher efficiencies than the conventional 3J -namely, inverted metamorphic (IMM) solar cells, solar cells including dilute nitride subcells, multijunction devices fabricated through wafer bonding, among others-have not yet fully demonstrated a radiation hardness comparable to the 3JSC case (see for instance Ref: [2]).…”