Photoluminescence Analysis of Proton Irradiation Effects in Cu(In,Ga)Se₂ Solar Cells

Abstract

We investigated proton irradiation effects on Cu(In,Ga)Se 2 (CIGS) solar cells with a structure of ZnO/CdS/CIGS using photoluminescence (PL) spectroscopy. After proton irradiation, near band-edge emission from the CIGS layer was considerably reduced, while deep-level emission emerged at 0.8 eV. Subsequent annealing restored the intensity of the near band-edge emission slightly, and reduced the 0.8 eV band substantially. An anomalous spectral variation caused by the annealing suggests that the 0.8 eV band does not originate from a single irradiation-induced defect. After the irradiation, the 1.35 eV emission from the CdS layer was moderately reduced, and the band-edge emission from the ZnO layer had disappeared. These bands recovered to the initial state after the annealing. Qualitative correlation was observed between the PL properties and the electrical properties of the cell.

Effects of Proton Irradiation on Optical and Electrical Properties of Cu(In,Ga)Se2 Solar Cells

“…The X-ray diffraction patterns and surface scanning electron microscope images did not change under proton irradiation (data not shown). Previous reports also showed that PL peak intensities due to deep level defects in CIGS decreased under electron 16) and proton 8) irradiation.…”

“…1,2) In fact, irradiation-damage studies of CIGS solar cells in space have revealed that their electrical properties show relatively less degradation due to proton, [3][4][5][6][7][8] electron, 3,6,[9][10][11] or gamma-ray 12) irradiation than Si solar cells, making them more suitable for space satellite applications, which require solar cells to function for several years. However, despite many reports on CIGS solar cells, [3][4][5][8][9][10][11][12] there have been few reports on irradiated CIGS thin films; hence, the degradation and/or resistance mechanism of irradiated CIGS solar cells remains to be clarified. 6,7) The mechanism of solar cell degradation, as researchers have gradually come to realize, is a complex phenomenon.…”

“…Thin film solar cells composed of polycrystalline Cu(In,Ga)Se 2 (CIGS) show high conversion efficiency and excellent radiation tolerance, making them very promising for space applications. 1,2) In fact, irradiation-damage studies of CIGS solar cells in space have revealed that their electrical properties show relatively less degradation due to proton, [3][4][5][6][7][8] electron, 3,6,[9][10][11] or gamma-ray 12) irradiation than Si solar cells, making them more suitable for space satellite applications, which require solar cells to function for several years. However, despite many reports on CIGS solar cells, [3][4][5][8][9][10][11][12] there have been few reports on irradiated CIGS thin films; hence, the degradation and/or resistance mechanism of irradiated CIGS solar cells remains to be clarified.…”

Influence of electron irradiation on electroluminescence of Cu(In,Ga)Se2solar cells

“…Protons and electrons with energy of over MeV, which can generate all kinds of Frenkel-pairs in CIGS, reduced the EL intensity from CIGS solar cells. 14) The particles can also generate recombination centers in material that is able to degrade cell performance. However, the EL emission intensity was found to increase with increasing electron fluence in this case, although it remains veiled whether the defects affect to increase in the intrinsic, or decrease in the number of the non-radiative recombination centers.…”

Optical and Solar Cell Properties of Alpha-ray, Proton, and Gamma-ray Irradiated Cu(In,Ga)Se2 Thin Films and Solar Cells

“…In fact, CIGS-based solar cells have been reported to show excellent radiation tolerance in space. 1) Irradiation damage studies of CIGS-based solar cells have revealed that their electrical properties are not degraded by proton, [2][3][4][5][6][7] electron, 2,5,[8][9][10] or gamma-ray 11) irradiation, unlike Si-based solar cells. However, although many studies have been reported on CIGS-based solar cells, [2][3][4][7][8][9][10][11] there have been only a few reports on irradiated CIGS thin films.…”