ZnO films using a precursor solution irradiated with an electron beam as the cathode interfacial layer in inverted polymer solar cells

Abstract

We demonstrate the possibility of irradiating sol-gel ZnO with an electron beam (EB-ZnO) to modify sol-gel ZnO, and EB-ZnO is explored as a cathode interfacial layer for inverted polymer solar cells. We investigate the effect of EB-ZnO on the surface, optical and electric properties of sol-gel ZnO films through morphology, chemical composition, optical band gap shift, various defect excitations (photoluminescence) and work function measurement. Oxygen vacancies and the formation of nitrogen on the surface of EB-ZnO films contribute to the formation of n-type degenerated EB-ZnO films. The electric properties of EB-ZnO strongly depend on the adsorbed dose, and EB-ZnO with a suitable dose of 100 kGy improved the power conversion efficiency of inverted polymer solar cells based on PTB7-Th: PC71BM from 8.05% for non-treated sol-gel ZnO to 9.36% for EB-ZnO with an enhanced fill factor.