Research On Surface Treatment And Anti-Reflection Properties Of V₂O₅/FTO Composite Thin Films

Fluorine-doped tin oxide（FTO）,as a kind of transparent conductive material with high optical transmittance,has been widely used in various display fields and is also one of the important materials for the preparation of solar cell electrodes.Due to its advantages of low cost,high optical transmittance and good thermal/chemical stability,the FTO film has gradually replaced other transparent conductive films and becomes one of the preferred materials for fabricating solar cell electrodes.However,the optical performance improvement of the single-layer FTO film is very limited,which cannot meet the needs of rapidly developing optoelectronic devices.Some studies have shown that vanadium pentoxide（V₂O₅）as an anti-reflection coating combined with a thin film can effectively improve its anti-reflection performance,but there are few reports on the performance optimization of V₂O₅-based composite films by laser surface treatment.Based on these,the surface optimization treatment of V₂O₅/FTO composite films was carried out by laser annealing and laser etching of anti-reflection grating structures.The effects of defocusing amount,laser fluence,scanning speed and anti-reflection structure parameters on the optical properties of the composite films were studied,and the technological parameters for the optical performance optimization of the composite films were discussed.Some meaningful results were obtained.1.Laser annealing on the surfaces of V₂O₅/FTO composite films prepared by sol-gel method was performed by using a nanosecond pulsed laser with 532 nm wavelength.The effects of defocusing amount,laser fluence and scanning speed on the surface morphology,reflectance and transmittance of the composite films were mainly studied.The experimental results revealed that when the defocus was 1.5 mm,the laser fluence was 0.2 J/cm²and the scanning speed was 15 mm/s,the composite film possessed the best optical properties.The average reflectance in the visible region（400–800 nm）was 16.88%,which was 2.42%lower than that of the unannealed composite film（19.3%）.The average transmittance achieved 69.34%.2.The optimal V₂O₅/FTO composite film after laser annealing was adopted as the research object,on whose surface laser etching was employed to fabricate anti-reflection grating structures.The influences of groove depth and groove spacing（i.e.,scanning spacing）on the surface morphology,reflectance and transmittance of the composite films were mainly investigated.The experimental results indicated that the optical properties of the composite film were the best under a laser fluence of 2.2J/cm²（a groove depth of 0.385μm）and a scanning spacing of 80μm（a groove spacing of 80μm）.The average reflectance in the visible region（400–800 nm）was11.84%,which was 5.04%lower than that of the composite film without etching grating structure.The average transmittance achieved 82.19%.The fabrication of grating structures greatly improved the anti-reflection performance of the composite films.3.The optimal V₂O₅/FTO composite film after laser annealing was adopted as the research object,on whose surface laser etching was utilized to fabricate bidirectional anti-reflection grating structures.Using the best laser etching parameters determined above,the effects of grating inclination angle（30°,60°and 90°）on the surface morphology,reflectance and transmittance of the composite films were mainly explored,and compared with the film sample with fabricating unidirectional anti-reflection grating structure.The experimental results showed that the bidirectional grating structure was more conducive to improving the anti-reflection performance of the composite film.As the inclination angle was 90°,the composite film reached the best optical performance,with an average reflectance of 8.98%and an average transmittance of 87.18%in the visible region（400–800 nm）.