Investigating the impact of parametric optimization on efficiency and radiation degradation performance of triple junction InGaP/InGaAs/Ge solar cells

This computational study presents a comprehensive optimization approach adapted to achieve an enhanced power conversion efficiency of an InGaP/InGaAs/Ge lattice-matched triple junction solar cell through Crosslight APSYS, a TCAD device simulation package. The study focuses on optimizing device parameters, i.e., layered materials and their thicknesses and doping concentrations to improve efficiency and analyze radiation-induced performance degradation. Prior to the parametric optimization, the cell’s design was benchmarked against a typical commercially available triple junction solar cell with an efficiency close to 31%. Considering lattice matching and layer-wise bandgap energies, thickness and doping concentrations were systematically varied to identify optimum values. Our study demonstrates a decent enhancement in the efficiency of the optimized cell, reaching a value as high as 35.10%. Upon introducing the cell under particle irradiations, by means of introducing charge carrier traps, the power conversion efficiency is observed to degrade to ca. 30% and 31% upon 1 MeV electron irradiation with a fluence of 10¹⁶ cm⁻² and 10 MeV proton irradiation with a fluence of \(10^{13} {\text{ cm}}^{ - 2}\), respectively. Additionally, Shockley–Read–Hall trap assisted recombination is observed to be prominent in the n-InGaAs layer and is relatively negligible across the other two active layers of the cell. Consequently, radiative recombination is observed to be suppressed in the middle subcell with increased irradiation fluences, as the traps densities are increasingly introduced with the irradiation. Both the recombination rates remain relatively unaffected in the bottom subcell with increase in irradiation fluences. Pre-optimization efficiencies under similar irradiation were ca. 27% and 28%. Though degradation levels were similar, the optimized cell showed ca. 3% higher open-circuit voltage, ca. 4% higher short-circuit current and 10–11% better efficiency, demonstrating superior end-of-life performance for space applications.