A water/alcohol-soluble copolymer based on fluorene and perylene diimide as a cathode interlayer for inverted polymer solar cells

Abstract

A novel copolymer based on fluorene and perylene diimide with pendent amino groups, namely poly[2,9-bis(3-(dimethylamino)propyl)-5-methyl-12-(7-methyl-9,9-dioctyl-9H-fluoren-2-yl)anthra(2,1,9-def:6,5,10-d′e′f′)diisoquinoline-1,3,8,10(2H,9H)-tetraone] (PF-PDIN), has been synthesized and developed as a cathode interlayer for inverted polymer solar cells (I-PSCs). PF-PDIN shows good alcohol solubility and uniform film morphology. The device with the configuration of ITO/PF-PDIN/P3HT:PC₆₁BM/MoO₃/Ag exhibits a power conversion efficiency (PCE) of 3.54%. The resulting device shows higher efficiency and better stability relative to the device using an organic small-molecule analogue, 2,9-bis(3-(dimethylamino)propyl)anthrax(2,1,9-def:6,5,10-d′e′f′)diisoquinoline-1,3,8,10(2H,9H)-tetraone (PDIN), as the cathode interlayer. This work indicates that PF-PDIN is a new promising candidate cathode interlayer for highly efficient and stable PSCs.