Indexed on: 25 Jan '17Published on: 25 Jan '17Published in: ACS Applied Materials & Interfaces
In this study, we report efficient inverted bulk heterojunction (BHJ) polymer solar cells (PSCs) via utilizing an ultrathin layer of lithium sulfonated polystyrene (LiSPS) ionomer to reengineer the surface of the solution-processed zinc oxide (ZnO) electron extraction layer (EEL). The unique lithium-ionic conductive LiSPS contributes to enhanced electrical conductivity of the ZnO/LiSPS EEL, which not only facilitate charge extraction from BHJ active layer, but also minimize the energy loss within the charge transport processes. In addition, the organic-inorganic LiSPS ionomer well circumvents the coherence issue of the organic BHJ photoactive layer on the ZnO EEL. Consequently, the enhanced charge transport and the lowered internal resistance between the ZnO/LiSPS EEL and BHJ photoactive layer give rise to a dramatically reduced dark saturate current density and significantly minimized charge carrier recombination. As a result, an approximatively 25% enhancement in efficiency is observed from the inverted BHJ PSCs with the ZnO/LiSPS EEL. These results indicate our method provides a simple but effective way to approach high efficiency from the inverted PSCs.