ZnO nanorod hemispherical light scatterers for thin film solar cell applications

Abstract Efficient light management is crucial for enhancing the performance of thin film solar cells. This study investigates the use of solution-processed zinc oxide (ZnO) nanorod (NR) arrays with novel hemispherical nanostructures as light scatterers for thin film solar cell applications. The morphology of the ZnO NR arrays is controlled by varying the seed layer deposition method [slot-die coating versus physical vapour deposition (PVD)] and thickness. A thin slot-die coated seed layer (i.e. ∼100 nm) promotes the formation of hemispherical nanostructures, which exhibit enhanced light-scattering properties compared with vertically aligned NRs grown on PVD seed layers. This study reveals that in-plane stress induced by lattice mismatches along the c -axis of NRs causes the thin seed layer to arch upwards, developing these hemispherical light scatterers. COMSOL simulations further reveal that the enhanced scattering is due to a combination of total internal reflection and refraction within the NR arrays. The deposition of a CdS buffer layer on the hemispherical arrays further improves light scattering, achieving a high average haze value of 0.72 in the wavelength range from 400 nm to 1000 nm. Bringing together the light-scattering features of these structures, SCAPS simulations demonstrate that incorporation of ZnO NR hemispherical light scatterers into cadmium telluride solar cells can significantly enhance photogenerated carrier collection, potentially enabling thinner absorber layers and reduced material consumption. This work offers a promising pathway towards cost-effective and high-efficiency thin film solar cells through innovative nanostructure design and solution-based fabrication techniques.