Synthesis of Phenanthro[1,10,9,8-cdefg]carbazole-Based Conjugated Polymers for Green-Selective Organic Photodiodes

A push–pull-type donor copolymer, named PP-TPD, was synthesized with the Suzuki coupling reaction using 6H-phenanthro­[1,10,9,8-cdefg]­carbazole (PCZ) as the donor unit and 1,3-bis­(5-bromothiophen-2-yl)-5-octyl-4H-thieno­[3,4-c]­pyrrole-4,6­(5H)-dione (TPD) as the acceptor unit. The synthesized PP-TPD was systematically investigated in terms of crystallinity and thermal, electrical, electrochemical, and optical properties. PP-TPD revealed green-selective absorption with a narrow full width at half-maximum of 138 nm. Green-selective organic photodiodes (OPDs) were constructed using PP-TPD as the green-absorbing donor and ZnO as the nonabsorbing acceptor material. The fabricated OPDs exhibited an extremely low dark current of 0.68 nA/cm² at −5 V and a high detectivity above 10¹² Jones at 550 nm. Moreover, they showed a sufficiently high 3-dB frequency and a linear dynamic range, similar to those of ideal-operating OPDs. The origin and physics background of the observed low dark current and high detectivity are discussed in detail.