Study On Effect Of Micro-nano Structures Produced By Femtosecond Laser Irradiation Of Ga As Solar Cells Surface On Antireflection Performance

With the deployment of the national space strategy plan,space satellite technology has become the main technology that countries in the world have been striving to develop in the 21st century.However,the space-satellite space power acts as the main component of space satellites,its photoelectric conversion efficiency is the key factor in the development of space technology.As a space power source,multi-junction layer solar cell can effectively improve the photoelectric conversion efficiency of the solar cell,but the preparation process is complicated and the cost is high,thus it is difficult to apply in industrial production.The surface microstructures can suppress the reflection of incident light,enhance the absorption of light on the absorption layer surface of the cell,thus improve the photoelectric conversion efficiency of the solar cell.Therefore,researchers are committed to the anti-reflection studies of surface microstructures.In this paper,GaAs solar cell as the research object irradiated by femtosecond laser to prepare the micro/nano-structures for anti-reflection,which provides an effective experimental foundation for improving the photoelectric conversion efficiency of the GaAs cells.In this paper,the surface of GaAs/Ge single-junction heterogeneous cells were processed by a suitable processing environment and optimized femtosecond laser process parameters.Simultaneously,femtosecond lasers were used to irradiate different battery materials(GaAs/Ge single-junction hetero cells and GaAs double-junction hetero cells)to fabricate microstructures.The interactions between different microstructures and incident light of different wavelengthswere analyzed,andthe formationmechanismof different microstructures was analyzed through experiments and schematics.The major conclusions were attained as following:(1)The effects of different processing environments(air,ethanol,distilled water)on the microstructure fabricated by femtosecond lasers on GaAs/Ge single junction heterogeneous cells surface were studied.Respectively characterized the cell surface processed by the femtosecond laser in different processing environments.The results showed that the micro-structures prepared in distilled water environment are 1-2orders of magnitude smaller than in the air environment,and more evenly distributed,which depth range is controlled at 100-350nm.The microstructure prepared in distilled water environment is more complex than in ethanol environment,the density of protrusion structures is relatively large,and more nanopores are distributed around the protrusion structures.(2)In distilled water,the effects of the change of laser processing parameters such as energy density and scanning speed on the morphology of microstructures were studied,and the optimum process parameters(7.9J/cm~2,2.2mm/s)were obtained.Then the composite nanostructures(CNs)were successfully prepared on the surface of GaAs/Ge single-junction heterogeneous cell.The CNs structures consist of nano-pores and nano-protrusions,with a size range of 300-500nm.The average reflectance(300-1700nm)of the cell surface covered by the CNs is reduced from30.84%to 8.9%.The anti-reflection mechanism of the CNs structure is on the one hand its multiple reflection to incident light in short wavelength band,and on the other hand it acts as the effective refractive index layer to reduce the reflection of the incident light in long wavelengths band.(3)One-dimensional micro-nano composite grating structures(ID-CGs)were fabricated on the surface of GaAs/Ge single-junction cells by femtosecond laser irradiation in air environment.The average reflectance of the GaAs/Ge single-junction cell surface was reduced from 30.84%to 7.17%in the 300-1700nm wavelength band.Simultaneously,similar grating structures were fabricated on the surface of GaAs double-junction cell.The average reflectance of the double-junction cell was reduced from 38.36%to 9.09%within the same wavelength band.The anti-reflection mechanism of the CNs structures is due to the combination of light trapping effect and effective medium effect.The micro-scale grating structures generate light trapping effect,and the composite nano-structure inside the grating structures form an effective medium effect.