Eliminating light soaking effect of inverted polymer solar cells functionalized with a conjugated macroelectrolyte electron-collecting interlayer

To overcome the light soaking and hysteresis characteristics in indium tin oxides (ITO)/poly[(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) based bulk-heterojunction polymer solar cells, a smart gate dielectrics nano-interfacial layer was incorporated by spin-coating an ultrathin polyetherimide (PEI) between ITO and PFN electron extraction layer. The ultrathin PEI micromolecule can effectively fill the surface defects of ITO and surmount electron transport barrier upon forming attached dipoles. The passivation surface decreased the total interfacial electron localized state and electron transfer barrier, which could re-modulate the interfacial property of buffer layer and facilitate electron collection. The additional insulating layer can influence the photoconductivity response and consequently restrain photocurrent hysteresis phenomena, leading to the improved power conversion efficiency. This finding would be helpful to achieve large-scale and low-cost polymer solar cells without light soaking effect.