A new alcohol-soluble electron-transporting molecule for efficient inverted polymer solar cells

A new electron-transporting material 4,7-diphenyl-1,10-phenanthroline-2,9-dicarboxylic acid (DPPA) was synthesized by modifying a n-type small molecule bathocuproine (BCP). DPPA inherits the excellent electron collecting and transporting property from BCP. In addition, DPPA demonstrated more stable and efficient performance than BCP under various processing conditions, likely due to the improved film quality and better hole-blocking. More importantly, this work brings up a fast and economical approach to obtain efficient, solution-processible buffer layer materials by modifying the existing functional molecules with corresponding electron-withdrawing/donating groups.