Ab initio electronic stopping power for protons in Ga$_{0.5}$In$_{0.5}$P/GaAs/Ge triple-junction solar cells for space applications

TL;DR

This study combines Monte Carlo simulations and ab initio RT-TDDFT calculations to analyze proton interactions with triple-junction solar cells, revealing how layer interfaces and channeling conditions influence electronic stopping power relevant for space radiation damage.

Contribution

It provides the first ab initio calculations of electronic stopping power in multilayer solar cell materials, considering interface and strain effects at relevant velocities.

Findings

Proton penetration varies with energy and channeling conditions.

Interface effects on energy loss are minor but increase at lower velocities.

Strain effects are negligible compared to bulk properties.

Abstract

Motivated by the radiation damage of solar panels in space, firstly, the results of Monte Carlo particle transport simulations are presented for proton impact on triple-junction Ga$_{0.5}$In$_{0.5}$P/GaAs/Ge solar cells, showing the proton projectile penetration in the cells as a function of energy. It is followed by a systematic {\it ab initio} investigation of the electronic stopping power for protons in different layers of the cell at the relevant velocities via real-time time-dependent density functional theory (RT-TDDFT) calculations. The electronic stopping power is found to depend significantly on different channeling conditions, which should affect the low velocity damage predictions, and which are understood in terms of impact parameter and electron density along the path. Additionally, we explore the effect of the interface between the layers of the multilayer structure on the energy loss of a proton, along with the effect of strain in the lattice-matched solar cell. Both effects are found to be small compared with the main bulk effect. The interface energy loss has been found to increase with decreasing proton velocity, and in one case, there is an effective interface energy gain.