Document Type : Regular Article
Authors
1 Renewable Energy and Environment Research Center, Corporation of Research and Industrial Development, Iraq
2 Department of Chemistry and Physics, Midweastrwan State University, USA
Abstract
A cost-effective DC glow discharge plasma system was used to deposit a 75 nm titanium dioxide (TiO2) antireflective coating on 5 cm2 crystalline silicon solar cells (initial efficiency 10.13%). The plasma-deposited TiO2 film was nanocrystalline: X-ray diffraction revealed mixed anatase/rutile phases with an average crystallite size of ≈17.6 nm and an optical band gap Eg ≈ 3.5 eV. Atomic force microscopy (AFM) showed a granular surface with average roughness Ra ≈50.7 nm (Rq ≈ 67.7 nm) and grain size ≈ 13.1 nm. Optical reflectance measurements indicated a significant reduction in surface reflectance across the visible spectrum after coating, consistent with enhanced light trapping. Photovoltaic current-voltage (I-V) characterization under standard illumination showed a marked increase in performance: the TiO2-coated cells exhibited improved short-circuit current density and an enhanced power conversion efficiency (PCE) of 11.56% (up from 10.13%), corresponding to 14.1% relative increase. Notably, the fill factor also improved (from 0.614 to 0.639), reflecting reduced resistive losses in the device. The efficiency gain is attributed to the high refractive index and engineered thickness of the TiO2 layer, which improve light coupling into the silicon absorber and reduce front-surface reflection. These results demonstrate that a thin (75 nm) plasma-deposited TiO2 antireflection coating can substantially lower front-surface reflectivity and boost the efficiency of silicon solar cells, offering a straightforward route to higher-performance devices.
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