Preparation Of Novel Wide - Spectrum Nanometer Three - Layer Antireflective Coatings By Sol - Gel Method

The traditional double-layer antireflection coating can not achieve ideal reflectioneffect in the wide spectrum range for GaAs-based multi-junction solar cell. It canalmost realize the absorption of the full solar spectrum at300~1800nm if theabsorption spectrum is further broadened. Therefore, in order to achieve idealreflection effect at350~1800nm, multi-layer antireflection coatings were designedand optimized in the wavelength range of350~1800nm by the TFC thin-film designsoftwar for triple junction solar cell structure GaInP/InGaAs/Ge in the paper. Theresults show reflection effect of Al2O3/SiO2/N(N is the nanometer SiO2film, therefractive index of which is less than1.4)is the ideal, effective reflectivity Reof whichis3.97％。The Al2O3layer and SiO2layer refractive index of which is adjustable, wereprepared on GaAs substrate by sol-gel technique for exploring the traceable basicexperimental parameters,to meet the needs of that Al2O3/SiO2/N triple-layernanometer antireflection coatings were prepared.The results were shown as:(1) Toobtain stable and transparent sol solution, the concentration of C9H21AlO3was controlled at0.68～1.04mol/L.Hydrolysis temperature is controlled at90℃～95℃. Reflux time should begreater than10hours.(2) The thickness of Al2O3layer and SiO2layer were increasedwith increase of withdrawal rate, were decreased with increase of temperature.(3) TheAl2O3layer was γ-AlOOH structure by200℃heat treatment, was γ-Al2O3phasewhen greater than200℃. Its refractive index was1.71, the thickness was controlled at74.1～161nm. The SiO2layer belong to amorphous, the refractive index and thicknessof were controlled at1.21～1.45and132.8nm～219nm.The Al2O3/SiO2/N triple-layer nanometer antireflection coatings were preparedon GaAs substrate. Through comparing the test and TFC simulation results, analysisobtained:(1)The measured reflected spectrum is close to theoretical reflectedspectrum at350～800nm.(2)Volatility of the measured reflected spectrum is larger, and have a gap for theoretical reflected spectrum at800～1800nm.(3)The averagereflectivity of the measured reflected spectrum was10.34％at all wavelength, has adeviation of26％to the theoretical reflected spectrum(7.65％).(4)To the triple junctionsolar cell structure GaInP/GaAs/Ge, the measured Reof Top Cell was14.64％, has adeviation of10.59％to the theoretical reflected spectrum(13.09％) at350～660nm; themeasured Reof Middle Cell was10.04％, has a deviation of7.47％to the theoreticalreflected spectrum(9.29％) at660～900nm; the measured Reof Bottom Cell was8.43％, hasa greater deviation of44.72％to the theoretical reflected spectrum(4.66％) at900～1800nm.