Photoluminescence Analysis of Injection-Enhanced Annealing of Electron Irradiation-Induced Defects in GaAs Middle Cells for Triple-Junction Solar Cells

Photolumineseenee measurements are carried out to investigate the injection-enhanced annealing behavior of electron radiation-induced defects in a GaAs middle cell for GaInP/GaAs/Ge triple-junction solar cells which are irradiated by 1.8 MeV with a fluence of i ~ 1015 cm-2. Minority-carrier injection under forward bias is observed to enhance the defect annealing in the GaAs middle cell, and the removal rate of the defect is determined with photoluminescenee radiative efficiency recovery. Furthermore, the injection-enhanced defect removal rates obey a simple Arrhenius law. Therefore, the annealing activation energy is acquired and is equal to 0.58eV. Finally, in comparison of the annealing activation energies, the E5 defect is identified as a primary non-radiative recombination center.

Photoluminescence Analysis of Electron Damage for Minority Carrier Diffusion Length in GaInP/GaAs/Ge Triple-Junction Solar Cells

Photoluminescence（PL） measurements are carried out to investigate the degradation of GaInP top cell and GaAs middle cell for GaInP/GaAs/Ge triple-junction solar cells irradiated with 1.0, 1.8 and 11.5 MeV electrons with fluences ranging up to 3 × 10^15, 1 × 10^15 and 3 × 10^14 cm^-2, respectively. The degradation rates of PL intensity increase with the electron fluence and energy. Furthermore, the damage coefficient of minority carrier diffusion length is estimated by the PL radiative efficiency. The damage coefficient increases with the electron energy. The relation of damage coefficient to electron energy is discussed with the non-ionizing energy loss（NIEL）, which shows a quadratic dependence between damage coefficient and NIEL.

Nano-sphere surface arrays based on GaAs solar cells

In this paper,we present our efforts on simulating and analyzing the effect of two-dimensional nano-sphere surface array on the characteristic of GaAs solar cells.Based on the scattering and diffraction theory of the photonic crystals,the simulation results show that the distance of adjacent nano-spheres(D)has the pronounced influence on the conversion efficiency and exhibits much poor tolerance,the absolutely conversion efficiency is reduced by exceeding of 2%as the D varies from 0 to 1μm,in addition,the lower conversion efficiency(<18%)is exhibited and almost remains unaltered when the D is of>2μm.The radius(R)of nano-spheres demonstrates much great tolerance.For D=0,the solar cells exhibit high conversion efficiency(>20%)and the efficiency is only varied by less than 1%when R is varied in a very wide region of 0.3-1.2μm.One can also find out that there is good tolerance for efficiency around the optimal value of refractive index and there is only about 0.2%decrease in final cell efficiency for around±24%variation in the optimal values,which implys that it does not demand high precision processing equipment and the whole nano-sphere array could be fully complemented using self-assembled chemical methods.