Enhancing solar cell efficiency through ZnO antireflection films

Abstract

Surface reflection reduces the amount of light reaching the solar cell and can lower its photovoltaic performance. Therefore, antireflection coatings are important for reducing optical losses and improving the solar cell performance. In this study, ZnO/PMMA films were coated on the cover glass of the solar cell using a sol-gel dip-coating technique. PMMA was added to the ZnO matrix as a porogen to form porous ZnO films. The effect of PMMA concentration in the dip-coating solution on optical properties, crystal and chemical structure, and photovoltaic conversion efficiency was investigated. XRD and FTIR analyses proved that ZnO was successfully obtained both alone and in the presence of PMMA. In addition, FESEM and optical microscopy images revealed that the pores on the surface were observed to increase as the PMMA content of the ZnO/PMMA film increased. ZnO/PMMA coated glass slides exhibited higher transmittance, lower reflectance and refractive index values in the visible wavelength range compared to pure ZnO coated glass slides. Among the investigated samples, the film containing 3 wt.% PMMA exhibited the most favorable combination of optical and photovoltaic properties. The UV-Vis spectrum showed a maximum transmittance of 92.50%, a lowest reflectance of 6.35% and a lowest refractive index value of 1.64 at a wavelength of 650 nm with the PMMA/ZnO film containing 3 wt.% PMMA on a glass slide. Adding the PMMA phase to the ZnO film resulted in approximately a 6% increase in solar cell efficiency. The pore formation mechanism of PMMA could be attributed to the aforementioned improvement in the light transmittance and photovoltaic conversion efficiency. The present findings demonstrated that the addition of PMMA provided a simple solution-based route to modify the porosity, refractive index, optical transmittance/reflectance, and photovoltaic performance of ZnO films. Therefore, ZnO/PMMA coatings might represent a promising alternative approach for antireflection applications in silicon solar cells.