Electron radiation–induced degradation of GaAs solar cells with different architectures

Abstract

The effects of electron irradiation on the performance of GaAs solar cells with a range of architectures is studied. Solar cells with shallow and deep junction designs processed on the native wafer as well as into a thin‐film were irradiated by 1‐MeV electrons with fluence up to 1×1015 e−/cm2. The degradation of the cell performance due to irradiation was studied experimentally and theoretically using model simulations, and a coherent set of minority carriers' lifetime damage constants was derived. The solar cell performance degradation primarily depends on the junction depth and the thickness of the active layers, whereas the material damage shows to be insensitive to the cell architecture and fabrication steps. The modeling study has pointed out that besides the reduction of carriers lifetime, the electron irradiation strongly affects the quality of hetero‐interfaces, an effect scarcely addressed in the literature. It is demonstrated that linear increase with the electron fluence of the surface recombination velocity at the front and rear hetero‐interfaces of the solar cell accurately describes the degradation of the spectral response and of the dark current characteristic upon irradiation. A shallow junction solar cell processed into a thin‐film device has the lowest sensitivity to electron radiation, showing an efficiency at the end of life equivalent to 82% of the beginning‐of‐life efficiency.

Challenges for the future of tandem photovoltaics on the path to terawatt levels: a technology review

“…These radiation belts can cause severe damage to the satellites' solar cells and microelectronic circuits. In the case of solar cells, this radiation significantly reduces the minority carrier lifetimes and the quality of the interfaces by creating lattice defects [64]. Silicon-based devices were particularly shown to degrade, leading to questions whether solar cells would be useful in space at all [19].…”

Limiting mechanisms for photon recycling in thin‐film GaAs solar cells

“…The difference in J 01 observed between the different sized cells from structure C is due to the increase in f PR granted by the reduced C f in the 1.0 × 1.0 cm 2 cells. J 0, diff , on the other hand, is limited by the quality of the hetero‐interfaces, 10,30 so in order to fully benefit from the increase in photon recycling, it is important that J 0, rad dominates the dark curve at V ≈ V oc , and therefore J 0, diff and J 0, perim should be as low as possible.…”

“…When comparing single junction GaAs solar cells in the thin‐film or wafer‐based designs, the advantages of the wafer‐based architecture are mainly the more mature and quick processing route. The thin‐film architecture presents as main advantages the reduced weight and potential of reduced costs with the removal and reuse of the wafer, 3‐5 possibility of utilizing thinner epilayers with the application of a back reflector that increases the light optical path 6‐8 ; increased resilience to particle irradiation for space application due to the reduced thickness, 9,10 bendability, 11‐14 and increased photon recycling due to reflectance of emitted photons 15‐19 …”

“…In the same study, it was shown that the rear reflectance has a direct impact on the solar cell parameters, most drastically affecting the open circuit voltage ( V oc ), due to a more efficient re‐absorption of radiatively emitted photons. Since then, multiple studies have been conducted towards increasing photon recycling in thin‐film solar cells, most of which present high quality crystal structures and efficiencies close to 25% 10,17‐24 . The main direction is to increase the reflectivity at the rear side, generally resulting in an increase of the devices' V oc .…”

A Theoretical Perspective of the Photochemical Potential in the Spectral Performance of Photovoltaic Cells

“…Recent theoretical approximations to the assessment of the spectral response and external quantum efficiency are diverse, (see, for instance, [ 10 ]), although the vast majority are based in computational programs solving the electrodynamic and electron and hole transport equations in semiconductor junctions under several assumptions; see, for instance, [ 11 , 12 , 13 , 14 ]. Analytical approaches are also reported in the phenomenological and quantum realms.…”