Direct evaluation of influence of electron damage on the subcell performance in triple-junction solar cells using photoluminescence decays

Abstract

Tandem solar cells are suited for space applications due to their high performance, but also have to be designed in such a way to minimize influence of degradation by the high energy particle flux in space. The analysis of the subcell performance is crucial to understand the device physics and achieve optimized designs of tandem solar cells. Here, the radiation-induced damage of inverted grown InGaP/GaAs/InGaAs triple-junction solar cells for various electron fluences are characterized using conventional current-voltage (I–V) measurements and time-resolved photoluminescence (PL). The conversion efficiencies of the entire device before and after damage are measured with I–V curves and compared with the efficiencies predicted from the time-resolved method. Using the time-resolved data the change in the carrier dynamics in the subcells can be discussed. Our optical method allows to predict the absolute electrical conversion efficiency of the device with an accuracy of better than 5%. While both InGaP and GaAs subcells suffered from significant material degradation, the performance loss of the total device can be completely ascribed to the damage in the GaAs subcell. This points out the importance of high internal electric fields at the operating point.

Radiation degradation characteristics of component subcells in inverted metamorphic triple-junction solar cells irradiated with electrons and protons

“…Moreover, we require a thorough understanding of what the PL intensity represents by considering the cell structures. We have proposed advanced analysis of solar cell operation using electroluminescence and time‐resolved PL characteristics , and our preliminary results have indicated that the luminescence efficiency of the InGaP cell under AM0, 1 sun illumination is not as high as we have expected from the relatively good cell performance . The reason for this is under investigation, but might explain the similarity with the InGaAs cells.…”

Space degradation of triple junction solar cells at low temperatures: II ‐electron irradiation

“…The degradation of diffusion current could result from the radiation‐induced defects acting as recombination centers. According to the study by Tex et al, in both electron‐irradiated GaInP and GaAs sub‐cells nonradiative recombination losses were observed 36 . When comparing the EOL properties of top and middle cells in dark, a larger degradation of diffusion current of the middle cell was observed in comparison to that of the top cell.…”

“…According to the study by Tex et al, in both electron-irradiated GaInP and GaAs subcells nonradiative recombination losses were observed. 36 When comparing the EOL properties of top and middle cells in dark, a larger degradation of diffusion current of the middle cell was observed in comparison to that of the top cell. However, the excess current of the top cell increased over 10 À5 A/cm 2 where it can affect the P MAX degradation whereas that of the middle cell was under 10 À6 A/cm 2 .…”

Electron and proton irradiation effect on the minority carrier lifetime in SiC passivated p-doped Ge wafers for space photovoltaics

“…Irradiation effects in TJ GaInP/GaInAs/Ge cells have been well studied at room temperature (RT) [9][10][11] or at low temperature [12,13]. In these studies, the Ge doping level is around 10 18 at.cm -3 .…”