Solution-processed interlayer of n-type small molecules for organic photovoltaic devices: Enhancement of the fill factor due to ordered orientation

• We synthesized alcohol/water-soluble small molecules.
• The synthesized molecules showed good solubility and thermal stability.
• DPPA showed strong π–π stacking interaction.
• QA and DPPA exhibited a more strongly ordered orientation.
• DPPA showed PCE of 7.9% with high FF (69.7%).

Novel alcohol/water-soluble small molecules were obtained using various p- and n-type backbones. The synthesized molecules were dissolved in organic solvents and highly polar solvents. The DPPA film exhibited strong shoulder peak at approximately 633 nm compared with the solution, which was due to the ordered orientation of DPPA. According to XRD measurements, a prominent diffraction peak at 20.1° was observed in the in-plane diffraction pattern of DPPA, which indicates an out-of-plane peak (010) due to the molecular packing by π–π stacking. A photovoltaic device containing DPPA exhibited an open-circuit voltage of 0.75 V, a current density of 15.1 mA/cm2, a fill factor of 69.0% and a power conversion efficiency of 7.9%. The photovoltaic device containing the DPPA derivative exhibited an improved power conversion efficiency compared with those containing BPA and QA (6.6% and 7.6%, respectively) due to the ordered orientation and packing of DPPA.

Figure optionsDownload as PowerPoint slide