Two major applications of III-V solar cells
- Use on satellites or in space
To use solar cells in space. Basically, there are three important points to consider.
(1) High energy conversion efficiency
The solar spectrum (AMO) on the satellite or in space is different from the surface < AM I. 5), and the difference is that the AMO is mainly short-wavelength light. The efficiency of solar cells will be poor for AMO, and can only reach 0.85~0.9 of AM 1.5. In the past, silicon solar cells and GaAs solar cells were mainly used on satellites. Generally, the efficiency of silicon solar cells for satellites is 12.7%~14.8%, and the high-efficiency silicon solar cells can reach 16.6%. The efficiency of single-junction GaAs solar cells is 19%, the efficiency of double-junction III-V solar cells is 22%, and the efficiency of triple-junction → V group solar cells is up to 26.8%.
( 2 ) Good radiation resistance
There are radiations of various energies in space, ranging from 50keV to 50 MeV. Space radiation can cause defects inside solar cells and reduce conversion efficiency. Therefore, if the factor of energy conversion efficiency attenuation is not considered into the system design. After the solar cell runs for a period of time. There will be a problem of insufficient power supply. Among single-junction solar cells, InP solar cells have the best radiation resistance, GaAs solar cells are the next, and silicon solar cells are the worst.
(3) Lightweight
The cost of launching a satellite or spacecraft is about $10,000 per stand, and in order to reduce the launch cost, the weight of the solar cell must be considered, or the power/weight ratio CW/kg). Silicon solar cells have a good advantage in this regard, and their weight per unit area is 0.13~0.50 kg/m2. The GaAs substrate is too heavy and has weak mechanical strength, so Ge is used as the substrate. 8 ~ 1. Okg/m2 0 For GaAs solar cells with Ge substrate or double junction and blue junction solar cells, the weight per unit area is still 0.8 ~ 1.0kg/m2 0
Due to its high energy conversion efficiency and good radiation resistance, III-V solar cells have gradually replaced silicon solar cells and are used in satellites and spacecraft.
In recent years, GaAs solar cells have replaced silicon solar cells on newly launched satellites. GalnP/GaAs/Ge solar cells are very similar to GaAs solar cells in the assembly and integration of solar cell modules, with higher energy conversion efficiency and as good radiation resistance as GaAs solar cells, while adding the advantages of high voltage and low current, Therefore, it is expected to become the next generation of space solar cells.
- Surface power generation
At present, solar power generation systems are widely used on the surface, from the power supply of small consumer products to large power plants. As mentioned in the preface, because the cost of Tian V solar cells is too expensive, Tian V solar cells are rarely used to make flat-panel solar cells except for special purposes such as satellites. According to the calculation, if we want to achieve an acceptable power generation cost, the concentrating conditions must be at least 400 times (400suns) above.
Using GalnP/GaAs/Ge high-efficiency solar cells, under high concentration conditions (such as 1000 suns), the power generation cost has the opportunity to drop to 0.07 US dollars / (kW h). At present, the annual production capacity of solar cells for space is about 0.5 MW. If these production capacities are converted into 1000 × concentrated solar cells, the annual power generation can reach about 0.5 GW. The current highest efficiency record for GalnP/GaAs/Ge solar cells is 34 % (AM 1.5 G, 210 suns), while the conversion efficiency of outdoor modules is 25 % 29 % at low concentration magnification. These data show that III-V solar The potential for batteries to be used for surface power generation is very high. Of course, before the actual large-scale investment in power generation systems, stable and reliable products are still required.
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