Interface engineering for highly efficient polymer solar cells

Abstract

Polymer solar cell (PSC) is regarded as the next-generation photovoltaic technology due to its low fabrication cost, light weight and high mechanical flexibility. The interfaces between the active layer and the two electrodes play key roles in improving the photovoltaic performance and device stability. This work aims to develop novel interfacial materials and cost-effective methods to modify the interface for highly efficient PSCs and understanding the mechanisms for the performance enhancement. Four approaches have been successfully employed to improve the efficiency of PSCs: (1) sodium compound-treatment of indium tin oxide (ITO) transparent electrode; (2) modification of ITO with zwitterions; (3) co-solvent treatment of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) buffer layer; and (4) chlorination of ITO. Efficiency of around 4% has been achieved after interface engineering. The enhancement is attributed to dipole-induced work function change, enhanced conductivity and morphology of PEDOT:PSS buffer layer, and change in surface energy of the substrate.