Design and photovoltaic performance analysis of electrodeposited ZnO microspheres/p-Si heterojunction energy harvesters

The present study introduced an innovative bottom-up technique to grow zinc oxide microspheres by the nanoplatelet assembling with the use of the template-free electrodeposition method. For investigating the photovoltaic performance of developed nanostructures, the ZnO seed layer was coated on the p-type silicon substrates using a radio frequency magnetron sputtering technique to act as an n-type layer and to form a p–n heterojunction. For the synthesis of ZnO microspheres, a photoelectrochemical cell with a Pt electrode as anode and the silicon samples as cathode was used. The electrolyte contained zinc chloride and potassium chloride. Glycerin was added to the aqueous solution, and its effect on the microsphere formation was investigated. The nanoplatelet average size was as low as few nanometers, and the deposited microsphere diameter was equal to 4 µm. The morphology of the samples showed the successful synthesis of ZnO nanoplatelets with different orientations, which may increase their light-trapping capability. The optical investigations revealed an increase in the photon absorption and photoluminescence intensity in the ZnO microspheres due to the multiple light scattering in the microspheres. A heterojunction thin film solar cell was designed by the metallization of ZnO/p-Si samples to study the power conversion capability of ZnO microspheres. The photovoltaic performance of developed devices was evaluated under a solar light simulator. The results indicated an efficiency improvement for the fabricated solar cells based on the ZnO microspheres, which might be attributed to their higher surface-to-volume ratio and increased exciton generation rate.