The well-aligned and highly uniform one-dimensional ZnO with organic dyes core/shell (ZNs) and ZnO with dyes and liquid crystals core/double-shells nanoarrays (ZNLs) with controllable lengths were fabricated as electron transport layers (ETLs) in inverted polymer solar cells (PSCs). Ditetrabutylammonium cis-bis(isothiocyanato)bis(2,2'-bipyridyl-4,4'-dicarboxylato) ruthenium(II) dye (N719) was presented to reduce the surface defects of ZnO nanoarrays (NAs). In addition, the shell modification could decrease the electron injection barrier between ZnO and active layer, thereby facilitating electron injection effectively and forming a direct electron transport channel into the cathode. Due to the orientation of nanoarrays and the self-organization of 3,6,7,10,11-pentakis(hexyloxy)-2-hydroxytriphenylene liquid crystals (LCs) in liquid crystalline mesophase and isotropic phase transition, the components of active layer would be driven rearrange and infiltrate among the interspaces of nanoarrays more orderly. The increased interfacial contact between cathode and active layer would benefit charge generation, transportation and collection. On the basis of these advantages, it was found the N719 shell and N719/LCs double-shells modifications of ZnO NAs could boost the photovoltaic performance of PSCs with the best power conversion efficiency (PCE) of 7.3% and 8.0%, respectively.
Keywords: core/double-shells; liquid crystals; nanoarrays; polymer solar cells.