Displacement Damage Equivalence of Neutron and Proton Radiations in Triple-Junction GaInP/GaAs/Ge Solar Cells

In this work, radiation effects in GaInP/GaAs/Ge triple junction solar cells irradiated by 3-, 5-, 10-, 60-, 100-MeV protons and 1-MeV equivalent neutrons are investigated. The external quantum efficiency (EQE), open-circuit voltage (
$V_{\mathrm {oc}}$
), maximum power (
$P_{\mathrm {max}}$
), and conversion efficiency (
$E_{\mathrm {ff}}$
) of solar cells are measured and compared. The Geant4 software is utilized to simulate non-ionizing energy loss (NIEL) with different particles. The physical mechanisms behind the different phenomena of device performance degradation due to neutron, low-energy proton, and high-energy proton irradiations at the same displacement damage dose (DDD) are analyzed. The proportion of primary knock-on atom (PKA) number produced by neutrons and low-energy protons is consistent with that of NIEL, but the proportion of PKA number produced by high-energy protons is not consistent with that of NIEL. The energy spectrum of PKA is investigated, and it is proposed that different energies and types of PKA may lead to different defect morphologies. The DDD method is used to determine the radiation damage equivalent between protons and neutrons, and the equivalent relationship between
$V_{\mathrm {oc}}$
,
$P_{\mathrm {max}}$
, and
$E_{\mathrm {ff}}$
is given. The results prove that the neutron source can be used as an alternative particle source for on-orbit solar cells to predict the performance degradation caused by protons.