Semiconducting junctions for solar energy production

Abstract

Solar energy has regarded as the latest comparatively sustainable energy source due to its low cost, eco-friendly and large scale the productibility. Silicon-based solar cells having a significant interest for many years. However, production and fabrication techniques are demanded which make the solar cells more cheaper. Therefore, thin film solar cells have emerged to be an alternative. Thin film technology is considered as inexpensive given that devices have a small amount of material and are established on varied pattern of light absorbing semiconductors. Furthermore, appropriate materials should be prepared, inexpensive, and show a stable behavior over long periods of operation. Zinc sulfide and zinc oxide are considered as the most favorable materials for heterojunction solar cells. This thesis aims to produce high efficiency and cost-effective solar cells by useing the energy that comes from the sun as an alternative and clean energy source. ZnS and ZnO thin films including silicon based solar cells were grown by using easy

and economic techniques which are chemical bath deposition, spin coating, and spray pyrolysis techniques. Properties of undoped and Na doped ZnS thin films were grown on glass and Si substrates by spray pyrolysis were investigated. Effect of annealing time and precursor solution amount of ZnO films on the optical properties were investigated. Structural, morphological, optical and electrical properties were examined by using XRD, SEM, UV-Visible spectrometry, and resistivity measurement. It had been found that the band gap energy of ZnS film was decreased to 3.42 eV from 3.66 eV and the resistivity of the film was decreased to 2.00 x105 Ω from 5.17 x105 Ω with increasing Na doping concentration. Performance of ZnS/Si heterojunction cell was improved to increase from 2.20% to 5.06% by Na doping. Moreover, the conversion efficiency of undoped and Na doped ZnS/Si is higher than undoped ZnO/Si fabricated under the same condition.