ISO 23038:2018 pdf free

ISO 23038:2018 pdf free.Space systems – Space solar cells – Electron and proton irradiation test methods
Solar cells, like all semiconductor devices, are subject to electrical degradation when exposed to particle irradiation. In terms of radiation damage to solar cells used in space, the primary particles of interest are electrons and protons. When these energetic particles are incident upon the solar cell material,they collide with the atoms of the crystal lattice of the solar cell. In these atomic collisions, energy is transferred from the incident particle to the target atom. This energy can be transferred in several ways. The majority of the energy is transferred through ionization of the target atom, where electrons of the target atom absorb the transferred energy and are promoted to higher energy levels. Another energy transfer mechanism is through nonionizing events, which results in the displacement of the target atom. If enough energy is transferred in a nonionizing event, then the displaced target atom may,in turn, displace other atoms, creating a cascade of displaced atoms. The displacement damage induced by the nonionizing interactions is the primary cause of most solar cell degradation.
When an atom is displaced in a lattice, the electron energy band structure of the material is disturbed,and localized energy levels can be created near the site of the defect. These defect energy levels can act to trap electrical charge carriers, thus restricting their ability to move through the material, which is characterized by a reduction in the minority carrier diffusion length. Since solar cell operation depends on the motion of photogenerated charge carriers through the material, these defect sites tend to degrade the solar cell performance.
The amount of displacement damage caused by an incident particle is a function of the type of incident particle (i.e. electron or proton), the particle energy, and the composition of the crystal lattice. The rate at which the incident particle transfers energy to the crystal lattice through nonionizing events is referred to as the nonionizing energy loss (NIEL). Electrons become more damaging as the incident electron energy increases. The opposite is true for protons, where the lower energy protons are the most damaging. Also, protons are significantly more damaging in comparison to electrons, primarily due to the increased proton differential scattering cross section for atomic displacements. There is a lower limit to displacement damage corresponding to the threshold energy for atomic displacements.This threshold energy is dependent on the semiconductor material that constitutes the solar cell.ISO 23038 pdf download.