Solar Cells For Space Use Research Articles

Materials Challenges in Photovoltaic Energy Generation in Space

AbstractVirtually all spacecraft employ photovoltaic energy conversion for continuous power generation. Compared to their counterpart on Earth, photovoltaic modules in the space environment face a unique set of performance requirements. Among the most demanding ones are the need to have the highest possible specific power output with regard to mass and surface area while showing as little degradation as possible under intense particle and ultraviolet radiation during lifetimes of up to 15 years. In addition, the thermomechanical stresses induced by temperature fluctuations up to 200°C are not to result in additional electrical degradation. This article briefly outlines the state-of-the-art design solution to meet these requirements before it focuses on current materials issues in two core areas: On the solar cell itself, which requires new materials systems and cell concepts to surpass the efficiency of the lattice-matched triple junction solar cell technology, and on materials issues concerning the encapsulation of solar cells for space use. Closely linked to these materials challenges are testing-related issues that arise in verifying the expected material behavior during extended periods in the space environment. These are discussed in conjunction with the materials challenges.

Effects of 0.28–2.80 MeV proton irradiation on GaInP/GaAs/Ge triple-junction solar cells for space use

GaInP/GaAs/Ge triple-junction solar cells were irradiated with 0.28, 0.62 and 2.80MeV protons with fluences ranging from 1×1010cm−2 to 1×1013cm−2. Their performance degradation is analyzed using current–voltage characteristics and spectral response measurements. The degradation rates of the short circuit current, open circuit voltage, and maximum power output increase with fluence, but decrease with increasing proton energy. It was also observed that the spectral response of the GaAs middle cell degrades more significantly than that of the GaInP top cell.

Low-energy proton irradiation effects on GaAs/Ge solar cells

Abstract This paper reports the low-energy proton irradiation effects on GaAs/Ge solar cells for space use. The proton irradiation experiments were performed with a fluence of 1.2×10 13 cm −2 , energies ranging from 0.1 to 3.0 MeV. The results obtained demonstrate that the irradiation with a proton energy of 0.3 MeV gives rise to the most degradation rates of I sc , V oc and P max of the solar cells with no coverglass, which is related to the proton irradiation-induced vacancies near the pn junction in GaAs/Ge cells. The degradation rates of I sc , V oc and P max of the solar cells with coverglass increase as the proton energy increases due to the cascade ions induced by collision processes. It is found that the coverglass has an obvious protection effect against the irradiation with the proton energy below 0.5 MeV.

5–20 MeV proton irradiation effects on GaAs/Ge solar cells for space use

This paper reports the high-energy proton irradiation effects on GaAs/Ge space solar cells. The solar cells were irradiated by protons with energy of 5–20 MeV at a fluence ranging from 1×10 9 to 7×10 13 cm −2 , and then their electric parameters were measured at AM0. It was shown that the I sc , V oc and P max degrade as the fluence increases, respectively, but the degradation rates of I sc , V oc and P max decrease as the proton energy increases, and the degradation is relative to proton irradiation-induced defect Ec−0.41 eV in irradiated GaAs/Ge cells.

High-efficiency silicon space solar cells

SHARP's activities on Si solar cells developments and features of Si solar cells for space use in comparison with GaAs solar cells are presented. Two types of high-efficiency silicon solar cells and the same kinds of high-efficiency solar cells with integrated bypass function (IBF cells) were developed and qualified for space applications. The NRS/LBSF cells and NRS/BSF cells showed an average of 18% and 17% efficiencies, respectively, at AMO and 28°C conditions. The IBF cells have P +N + diodes on the front surface to protect itself from reverse voltage due to shadowing. The designs and features of these solar cells are presented. The radiation tests results of these solar cells are also presented. The NRS/BSF cells showed lower degradation rate compared to conventional BSFR cells with the same thickness (100 μm). But the NRS/LBSF cells showed a higher degradation rate than the BSFR cells. The IBF cells showed almost the same radiation characteristics as the same kinds of cells without IBF. The results of radiation tests on these high-efficiency solar cells and the discussions about the radiation characteristics of them are presented. In the last section, the future silicon solar cell development plan is discussed.

Results of the solar cell experiment of the first Brazilian satellite

The first satellite of the Brazilian Complete Space Mission, launched on 9 February 1993, hosts a solar cell experiment (SCE). The objective of the SCE is to qualify in mission and real time the silicon solar cells for space use developed and manufactured in Brazil. The solar cells have the following characteristics: 4 cm 2 of area, base resistivity of 10 Ωcm and efficiency over 11% under AMO condition. The SCE is a small solar module composed by a single array of six silicon solar cells connected in series, laid down in an aluminium mechanical structure. The signal generated by the array is sent to a peak detector circuit located inside the mechanical structure. Three telemetry signals are available for the SCE behavior analysis, which are the peak detector output, the temperature sensor output, located inside the SCE mechanical structure under the solar array, and the attitude sensor signal, which gives the sunlight incidence angle with respect to the SCE plane. The SCE signal versus temperature curve is used to obtain the solar cell current versus voltage characteristic parameters values, based on the double exponential model, using a computational method developed to accomplish this task in real time, during the satellite lifetime. This work describes the solar cell experiment, the numerical methods and the analysis of the telemetry data received during the first two years in orbit. For this period, considering the standard deviation obtained in the output parameters, we can say that the radiation damage in the SCE solar cells is lower than expected when compared with data presented in the literature (1.7%) and those calculated from simulation in laboratory (1.0%). The analysis of the data indicates a degradation of the SCE solar cells around 0.5%.

High performance InGaAsP solar cells for space use

InGaAsP homojunction solar cells have been fabricated. InGaAsP layer of which the bandgap is 1.55 eV has been lattice-matched to GaAs substrate by LPE growth. Al 0.8Ga 0.2As has been introduced as window layer blocking layer. The best cell without an antireflection coating showed a conversion efficiency of 11.67% under AM 1.5 illumination, and the corresponding open-circuit voltage V oc , short-circuit current density J sc , and fill factor are 0.980 V, 15.99 mA/cm 2, and 0.745, respectively. InGaAsP cells have been lower temperature dependences of V oc and J sc as compared with InP and GaAs cells and have higher radiation resistance as compared with GaAs cells.