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

Abstract

The radiation response of In 0.5 Ga 0.5 P, GaAs, In 0.2 Ga 0.8 As, and In 0.3 Ga 0.7 As single-junction solar cells, whose materials are also used as component subcells of inverted metamorphic triple-junction (IMM3J) solar cells, was investigated. All four types of cells were prepared using a simple device layout and irradiated with high-energy electrons and protons. The essential solar cell characteristics, namely, light-illuminated current-voltage (LIV), dark current-voltage (DIV), external quantum efficiency (EQE), and two-dimensional photoluminescence (2D-PL) imaging were obtained before and after irradiation, and the corresponding changes due to the irradiations were compared and analyzed. The degradation of the cell output parameters by electrons and protons were plotted as a function of the displacement damage dose. It was found that the radiation resistance of the two InGaAs cells is approximately equivalent to that of the InGaP and GaAs cells from the materials standpoint, which is a result of different initial material qualities. However, the InGaAs cells show relatively low radiation resistance to electrons especially for the short-circuit current (Isc). By comparing the degradation of Isc and EQE, data, It was confirmed that the greater decrease of minority-carrier diffusion length in InGaAs compared with InGaP and GaAs causes severe degradation in the photo-generation current of the InGaAs bottom subcells in IMM3J structures. Additionally, it was found that the InGaP and two InGaAs cells exhibited equivalent radiation resistance of Voc, but radiation response mechanisms of Voc are thought to be different. Further analytical studies are necessary to interpret the observed radiation response of the cells.

Measurement of the limiting subcell in multijunction space solar devices by restricted‐wavelength‐range illumination

“…However, these deviations still remain within our estimated error. As expected by the literature, the tested cells are more sensitive to the irradiation dose than to the particle energy(): Congruently, we observe that the arising of a middle‐limited regime in EOL2 sample is fundamentally due to the employed high dose, which is more intense with respect to the case of EOL1 sample, rather than the kind and energy of the involved particles, as pointed out in previous studies. ()…”

“…() For these reasons, handling the peculiar multijunction current limitation effect requires that the 3J InGaP/InGaAs/Ge spatial devices are generally tailored in the so‐called top‐limited configuration, so that each middle and bottom cell supplies current levels higher than the top one: Then the final current of the cell is limited by the current produced by the top subcell. () Nevertheless, very high irradiation conditions can deteriorate the middle cell more than the other ones, so much that the response of the whole device is changed into a middle‐limited configuration, strongly affecting the final performance. ()…”

“…6,15 For these reasons, handling the peculiar multijunction current limitation effect requires that the 3J InGaP/InGaAs/Ge spatial devices are generally tailored in the so-called top-limited configuration, so that each middle and bottom cell supplies current levels higher than the top one: Then the final current of the cell is limited by the current produced by the top subcell. 2,6,16 Nevertheless, very high irradiation conditions can deteriorate the middle cell more than the other ones, so much that the response of the whole device is changed into a middle-limited configuration, strongly affecting the final performance. 15,17 Therefore, in order to suitably plan the limiting subcell during the development phase and to investigate irradiation-induced modifications during the testing phase, it is necessary to establish standard methods for characterizing subcells directly in their working configuration, ie, embedded in monolithic devices.…”

Effect of the Irradiation on Optical and Electrical Properties of Triple-Junction Flexible Thin Solar Cells for Space Applications

“…Specific previous studies on irradiated thick CTJ30 solar cells demonstrated that the introduction of this Bragg structure is able to increase the performance of the solar cell both in BOL and EOL conditions. The irradiation damage were evaluated by calculating the remaining factors, a figure of merit specifically employed in these kind of studies [22]. Indeed, the qualification campaign highlighted very good resistance under electron and proton irradiation [23].…”

Difference in space‐charge recombination of proton and electron irradiated GaAs solar cells

“…Therefore, Equation is no longer strictly valid. Taking in addition a linear increase of the back‐surface recombination velocity with DDD into account, the observed linear dependence can be rationalized.…”